Engine Controls Self-Diagnostics - 2.2l & 2.4l Pontiac Grand AM V

MODEL IDENTIFICATION

Vehicle and engine model is identified by Vehicle Identification Number (VIN). VIN is stamped on metal pad on top of left end of instrument panel, near windshield. See MODEL IDENTIFICATION and ENGINE IDENTIFICATION tables.

MODEL IDENTIFICATION

ENGINE IDENTIFICATION

INTRODUCTION

To properly diagnose and repair this vehicle, follow DIAGNOSTIC PROCEDURE under SELF-DIAGNOSTIC SYSTEM. If no Diagnostic Trouble Codes (DTC) are present and a no start condition exists, proceed to appropriate BASIC DIAGNOSTIC PROCEDURES article. If no DTCs are present and a driveability condition exists, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, ENGINE STALLS, etc.).

ON-BOARD DIAGNOSTICS

PCM is equipped with a self-diagnostic system which detects system failures or abnormalities. When a malfunction occurs, PCM will store a Diagnostic Trouble Code (DTC) and, if code is emissions related, illuminate the Malfunction Indicator Light (MIL) located on instrument cluster.

There are 2 paths for accessing on-board diagnostics. It is necessary to access information through both paths, as each path presents some different information.

1. Generic OBD-II This provides all generic codes and some OEM codes, serial data PIDs required for generic OBD-II and some OEM PIDs, monitor status, pending codes and freeze frame.
2. OEM All DTCs, all PIDs, failure records, enhanced scan tool information and all other OEM scanner functions.

Code Types

There are 4 types of DTC categories

1. Type "A" Emissions related. Illuminates MIL the first time DTC sets.
2. Type "B" Emissions related. Illuminates MIL if fault is active for 2 consecutive driving cycles.
3. Type "C" Non-emissions related. Does not illuminate MIL, but will illuminate SERVICE light.
4. Type "D" Non-emissions related. Does not illuminate MIL or SERVICE light.

Freeze Frame/Failure Records

PCM stores one freeze frame record for the first failed test that sets a DTC and illuminates MIL. Freeze frame will not be overwritten unless a misfire or fuel trim DTC is set. Failure records are stored when any DTC is set. Some PCMs can store up to 5 failure records. Failure records will be stored for all types of codes, whether or not the MIL is illuminated.

Typical data includes

1. Air/fuel ratio.
2. Airflow rate.
3. Fuel trim.
4. Engine speed.
5. Engine load.
6. Engine coolant temperature.
7. Vehicle speed.
8. Throttle position angle.
9. Manifold absolute pressure.
10. Injector base pulse width.
11. Loop status.

Monitors

1. Comprehensive Component Monitor Monitors PCM systems for opens, shorts grounds and out-of-range sensors. Also monitors rationality of sensors. Rationality is whether the sensors value is consistent with the operating conditions of the other sensors.
2. Misfire Monitor Monitors engine misfire using crankshaft sensor to determine location and severity of misfire. A catalyst damaging misfire will flash the MIL, and a non-catalyst damaging misfire is a normal type "B" code.
3. Fuel Trim Monitor Monitors short and long term fuel trim for being at maximum lean or rich limit.
4. Oxygen Sensor Monitor Monitors all oxygen sensors for maximum voltage level, minimum voltage level and lean rich/rich lean switching rate.
5. Oxygen Sensor Heater Monitor Monitors oxygen sensor heater by watching sensor's time-to-activity after a cold start.
6. Catalyst Monitor Monitors catalyst efficiency by comparing activity rate of precatalyst oxygen sensor and postcatalyst oxygen sensor.
7. EVAP Monitor Monitors EVAP system for large leaks, small leaks and purge flow.

Intermittent Trouble Code Determination

Note. Intermittent is a DTC or symptom, with a condition that cannot be duplicated. Before attempting to diagnose an intermittent condition, ensure powertrain diagnostic system check has been performed. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE) under SYSTEM CHECKS.

1. Duplicating Failure Conditions Freeze frame and failure records data contain the conditions present when DTC set. Review and record freeze frame and failure records data. Clear DTCs using scan tool. Turn ignition off and wait 15 seconds. Operate the vehicle under the same conditions noted in freeze frame and failure records data, as closely as possible. Vehicle must also be operating within conditions for running the DTC. See CODE ENABLE CRITERIA in appropriate DTC test. Monitor DTC Status for the DTC being tested. The scan tool will indicate Ran, when the enabling conditions have been satisfied long enough for the DTC to run. The scan tool will also indicate whether the DTC passed or failed. An alternate method is to drive the vehicle with the DVOM connected to a suspected circuit. An abnormal reading on the DVOM when the problem occurs, may help you locate the problem.
2. Wiring Harness & Electrical Connectors Many intermittent open or shorted circuits come and go with harness or connector movement caused by vibration, engine torque, and bumps or rough pavement. Test for intermittents by moving related connectors and wiring while monitoring appropriate scan tool data. With engine running, move related connectors and wiring while monitoring engine operation. Verify if harness or connector movement affects scan tool data display, component or system operation, or engine operation. Repair condition as necessary. Intermittents caused by electrical connectors are usually caused by poor electrical connections, terminal tension and/or wiring problems. Check for poor mating of connector halves, terminals backed out or not fully seated in connector body, improperly formed or damaged terminals or poor terminal tension. Also check for poor terminal-to-wire connections including terminals crimped over insulation, swollen and stiff sections of wire in suspect circuits, wires that are broken inside the insulation, pinched, cut or rubbed through wiring or wiring that is in contact with hot exhaust components. Repair condition as necessary.
3. Control Module & Component Power & Grounds Many vehicles have multiple circuits supplying power to control modules. Other components may have separate power circuits that may also need to be tested. Check connections at module or component connectors, fuses, and any intermediate connections between power source and the module or component. Ensure that the circuit can carry the current necessary to operate the component. Test all control module ground and system ground circuits. Control module may have multiple ground circuits. Other components may have separate grounds that may also need to be tested. Check grounds for clean and tight connections at the ground connection. Check the connections at the component and in splice packs, where applicable. Ensure that the circuit can carry the current necessary to operate the component.
4. Temperature Sensitivity An intermittent condition may occur when a component or connection reaches normal operating temperature. Condition may occur only when component or connection is cold, or hot. Use freeze frame and failure records, scan tool snapshot or vehicle data recorder to help diagnose this type of intermittent. If intermittent is related to heat, check for high ambient temperatures, underhood or engine generated heat, circuit generated heat due to a poor connection, or high electrical load. If intermittent is related to cold, check for low ambient temperatures or water intrusion.
5. Electromagnetic Interference & Electrical Noise Some electrical components or circuits are sensitive to Electromagnetic Interference (EMI) or other types of electrical noise. Check for misrouted wiring that is too close to high voltage or high current devices. Check for wires that are too close to secondary ignition components, electrical motors or the generator. Check for non-factory or aftermarket add-on accessories such as lights, 2-way radios, amplifiers, electric motors, remote starters, alarm systems, or cell phones. Test for open diode across AC compressor. Some relays may contain a clamping diode. Check that generator is operating properly.

DIAGNOSTIC PROCEDURE

Diagnosis of computerized engine control system should be performed in the following order

1. Ensure all engine systems not related to computer system are operating properly. DO NOT proceed with testing unless all other problems have been repaired. Diagnostic system check must be performed before using specific DTC testing procedure. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) or «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) .
2. If no DTCs are present and a driveability problem exists, refer to SYMPTOMS in appropriate TROUBLE SHOOTING - NO CODES article. Doing so will help identify proper system or component to check in appropriate SYSTEM & COMPONENT TESTING article.
3. After necessary repairs are made, clear DTCs, verify vehicle will enter "closed loop" operation and ensure DTC does not reset.

RETRIEVING DIAGNOSTIC TROUBLE CODES

DTCs are retrieved using a Tech 2 scan tool, or other OBD-II compatible scan tool connected to OBD-II 16-pin Data Link Connector (DLC). See POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE) or POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG). (Scheme 1) DLC is located below left side of dash.

Scheme 1

POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)

Note. Check for applicable Technical Service Bulletins (TSBs) before proceeding. DO NOT perform the following procedure if driveability conditions are not present. DO NOT turn ignition off during the following procedure or clear DTCs unless instructed to do so.

1. If vehicle does not crank, see appropriate STARTERS article in STARTING & CHARGING SYSTEMS. Ensure battery is fully charged and cables are clean and tight. Ensure PCM grounds are clean, tight, and in proper location. Install scan tool. If scan tool turns on, go to next step. If scan tool does not turn on, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article.
2. Turn ignition on, engine off. Attempt to establish communication with Body Control Module (BCM), Electronic Brake Control Module (EBCM), Instrument Panel Cluster (IPC), PCM, Sensing and Diagnostic Module (SDM), and Vehicle Theft Deterrent (VTD) module. If scan tool communicates with all control modules, go to next step. If scan tool does not communicate with all control modules, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
3. Attempt to start engine. If engine starts and idles, go to next step. If engine does not start and idle, see appropriate BASIC DIAGNOSTIC PROCEDURES article.
4. Select DTC display function for BCM, EBCM, IPC, PCM, SDM and VTD. If DTCs are present, record DTCs, which module set DTC and failure record for DTC. Go to next step. If DTCs are not present, go to step 7 .
5. If scan tool displays DTCs which begin with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article. If scan tool does not display DTCs which begin with "U", go to next step.
6. If scan tool displays DTC P0562, P0563, P0621 or P0622, see appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If scan tool does not display DTC P0562, P0563, P0621 or P0622, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .
7. If customer's concern is with the transmission, see appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS or MANUAL TRANSMISSIONS article. If customer's concern is not with the transmission, go to next step.
8. If customer's concern is MIL inoperative, see «MIL INOPERATIVE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__mil-inoperative-gasoline) under SYSTEM TESTS. If customer's concern is MIL always on, see «MIL ON STEADY (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__mil-on-steady-gasoline) under SYSTEM TESTS. If customer's concern is driveability, see appropriate TROUBLE SHOOTING - NO CODES article.

POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)

Note. Check for applicable Technical Service Bulletins (TSBs) before proceeding. DO NOT perform the following procedure if driveability conditions are not present. DO NOT turn ignition off during the following procedure or clear DTCs unless instructed to do so.

1. Ensure both fuel tanks are at least 1/4 full. Turn ignition off. Connect scan tool to Data Link Connector (DLC). Turn ignition on. If Malfunction Indicator Light (MIL) is illuminated, go to next step. If MIL does not illuminate, go to «MIL INOPERATIVE (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__mil-inoperative-cng) under SYSTEM TESTS.
2. Using scan tool, attempt to establish communication with Powertrain Control Module (PCM). If scan tool communicates with PCM, go to next step. If scan tool does not communicate with PCM, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article. If scan tool does not power up, go to SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
3. Using scan tool, attempt to communicate with Alternative Fuels Engine Control Unit (AF ECU). If scan tool displays alternative fuel data, go to next step. If scan tool does not display alternative fuel data, go to IGNITION RELAY DIAGNOSIS (2.2L - CAVALIER - CNG) under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article.
4. Select DTC display function for PCM and AF ECU. If DTCs are set, go to step 10 . If DTCs are not set, go to next step.
5. Using scan tool, command MIL off. If MIL turns off, go to next step. If MIL does not turn off, go to «MIL ON STEADY (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__mil-on-steady-cng) under SYSTEM TESTS.
6. Crank engine for a maximum of 10 seconds. If engine starts, go to next step. If engine does not start, go to step 9 .
7. Monitor Fuel Indicator Light (FIL) and select NGO ENABLE OUTPUT and INPUT parameters on scan tool to determine which fuel system is operating. If vehicle is operating on gasoline and FIL is not illuminated, go to fuel indicator light diagnosis in appropriate ANALOG INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. If NGO ENABLE OUTPUT and INPUT parameters do not indicate same data, go to FUEL SYSTEM UNWANTED SWITCH TO GASOLINE under FUEL SYSTEMS (2.2L - CAVALIER CNG) in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article.
8. Operate vehicle and observe/record engine data parameters on scan tool. If parameters are within operating range, go to step 11 . If parameters are not within operating range, go to DTC testing procedure that best matches out of range condition. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .
9. Remove CNG fuse (20-amp) located in underhood fuse block. Crank engine for at least 10 seconds. If engine starts and runs with fuse removed, reinstall fuse and go to IGNITION RELAY DIAGNOSIS (2.2L - CAVALIER - CNG) under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article. If engine does not start and run, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) .
10. Compare stored AF ECU DTCs with PCM DTCs. If DTCs are stored only in PCM, diagnose gasoline related DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If same DTCs are stored in AF ECU and PCM or only in AF ECU, diagnose alternative fuel (CNG) related DTCs. If multiple DTCs are set in both AF ECU and PCM, diagnose gasoline related DTCs first.
11. If driveability conditions exist, go to next step. If driveability conditions do not exist, go to step 13 .
12. Perform FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS (2.2L - CAVALIER CNG) in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article. If fuel system diagnosis locates and repairs a malfunction, go to step 15 . If fuel system diagnosis does not locate and repair a malfunction, attempt to diagnose by symptom. See appropriate TROUBLE SHOOTING - NO CODES article.
13. If symptoms exist for fuel gauge, fuel gauge selector or fuel indicator light, diagnose and repair as necessary. See SYSTEM TESTS in appropriate ANALOG INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. If symptoms do not exist for fuel gauge, fuel gauge selector or fuel indicator light, go to next step.
14. Ensure ignition is off. Remove CNG fuse (20-amp) from underhood fuse block. This will cause a forced switch to gasoline operation. Crank engine for at least 10 seconds. If engine starts and runs on gasoline, go to next step. If engine does not start and run on gasoline, go to FUEL PUMP RELAY DIAGNOSIS under FUEL SYSTEMS (2.2L - CAVALIER CNG) in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article.
15. Remove all test equipment except scan tool. Reconnect any disconnected components. Using scan tool, clear DTCs from AF ECU and PCM. Turn ignition off and wait 30 seconds. Start engine and operate vehicle. Monitor FIL and MIL operation. Observe vehicle performance and driveability. After operating vehicle check for DTCs in AF ECU and PCM. If vehicle operates on CNG with normal driveability, no FIL/MIL illumination and no set DTCs, system is okay. If vehicle does not operate on CNG with normal driveability, or FIL/MIL are illuminated or DTCs are set, go to step 1 .

CLEARING DIAGNOSTIC TROUBLE CODES

There are 3 methods to clear DTCs.

Scan Tool

Scan tool is preferable way to clear DTC information. Freeze frame and failure record data will also be cleared. PCM adaptive learning and system monitors will only be cleared for those system which had a stored DTC.

Disconnect Battery

Note. On many OBD-II systems, PCM will retain memory for an extended period of time with battery disconnected. Memory may be retained for several days.

Disconnecting PCM power or battery ground will clear all PCM memory including DTCs, freeze frame, failure records, adaptive learning and system monitors.

Warm-up Cycles

If fault that caused DTC to set is repaired, PCM will begin to count warm-up cycles. After 40 consecutive warm-up cycles with no further faults, PCM will automatically clear DTC from memory.

SCAN TOOL USAGE

Scan tool is a specialized tester which, when connected to DLC, can be used to diagnose on-board computer control systems by providing instant access to circuit voltage information without need to crawl under dash or hood to backprobe sensors and connectors.

Scan tool reduces diagnostic time dramatically by furnishing input data (voltage signals) which can be compared to specification parameters. They may also furnish information on output device (solenoids and motors) status. However, status parameters only indicate output signals have been sent to devices by PCM; they do not indicate whether devices have responded properly to signal. Verify proper response at output device using a voltmeter or test light.

A problem may exist even if DTCs are not present. Many driveability problems occur without setting DTCs.

Using a scan tool is the easiest method of checking sensor specifications and other data parameters. Scan tool is also useful in finding intermittent wiring problems by wiggling wiring harnesses and connections (key on, engine off) while observing data parameters.

Note. If erroneous voltage signals are suspected, verify tester information using a digital voltmeter and wiring schematic. If nonexistent codes are displayed, DO NOT use scan tool for diagnosis. Contact tester manufacturer for additional information.

Scan Tool Display

Note. OBD-II vehicles have options available in the scan tool DTC mode to display enhanced information available. However, to fully utilize information and procedures requires the use of a Tech 2 scan tool. See scan tool operator's manual for additional information.

The following are Tech 2 scan tool sub-menus in the DTC INFO and SPECIFIC DTC modes

1. DTC INFO MODE Used to search for specific type of stored DTC information. There are 7 choices in this mode. Technician may be instructed to test DTCs in a certain manner. Follow the affected DTC test procedures. To get complete description of any status, hit ENTER key before pressing the desired "F" key.
2. DTC STATUS This selection will display any DTCs that have not run during the current ignition cycle or have reported a test failure during this ignition up to a maximum of 33 DTCs. A DTC test that runs and passes will cause affected DTC to be removed from scan tool screen.
3. FAIL THIS IGN. This selection will display all DTCs that have failed during the present ignition cycle.
4. HISTORY This selection will display only DTCs that are stored in the control module's history memory. It will not display type "D" DTCs. It will display all type "A" and type "B" DTCs that have the MIL illuminated and have failed within the last 40 warm-up cycles. It will also display type "C" DTCs that have failed within the 40 warm-up cycles.
5. LAST TEST FAIL This selection will only display DTCs that have failed the last time the test ran. If type "A" or "B" DTCs are displayed, the last test may have ran during the previous ignition cycle. For type "C" DTCs, the last failure must have occurred during the current ignition cycle to be displayed as LAST TEST FAIL.
6. MIL REQUEST This selection will only display DTCs that are requesting MIL illumination. Type "C" DTCs cannot be displayed using this option. This selection will report type "B" DTCs only after MIL illumination has been requested.
7. NOT RUN SCC Not Run Since Code Clear option will display up to 33 DTCs that have not run since DTCs were last cleared. Since any displayed DTCs have not run, their condition (passing or failing) is unknown.
8. TEST FAIL SCC Test Fail Since Code Clear selection will display all active and history DTCs that have reported a test failure since the last time DTCs were cleared. DTCs that last failed more than 40 warm-up cycles before this option is selected will not be displayed.
9. FAILED SINCE CLEAR This message indicates the DTC has failed at least once within the last 40 warm-up cycles since the last time DTCs were cleared.
10. NOT RUN SINCE CL. Not Run Since Cleared message indicates that the selected diagnostic test has not run since the last time DTCs were cleared. Therefore, the diagnostic test status (passed or failed) is unknown. After DTCs are cleared, this message will continue to be displayed until the diagnostic test runs.
11. NOT RUN THIS IGN. Not Run This Ignition message indicates the selected diagnostic test has not run this ignition cycle.
12. TEST RAN AND PASSED This message indicates the selected diagnostic test has: Passed the last test. Ran and passed during this ignition cycle. Ran and passed since DTCs were last cleared. Test has not failed since DTCs were last cleared. If this message is displayed, repair is complete. If FAILED THIS IGN. message is displayed, repair is incomplete and further diagnosis is required.

POWERTRAIN CONTROL MODULE LOCATION

PCM is located inside right front fender on "J" body cars. PCM is located behind right side of dash on "N" body cars.

ALTERNATE FUEL ENGINE CONTROL MODULE LOCATION

AF ECU is located behind left front fascia, below headlight.

ALTERNATE FUEL ENGINE CONTROL UNIT

After replacing AF ECU or if program needs to be updated (flashed), refer to latest Techline information on AF ECU reprogramming.

POWERTRAIN CONTROL MODULE REPROGRAMMING

After replacing PCM or if program needs to be updated, refer to latest Techline information on PCM reprogramming. After reprogramming, perform CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE and PROGRAMMING THEFT DETERRENT SYSTEM COMPONENTS .

CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE

Note. Battery must be fully charged and in good condition. Scan tool connection at Data Link Connector (DLC) should be clean and tight before starting crankshaft position system variation learn procedure.

1. Close hood.
2. Block drive wheels and set vehicle parking brake.
3. Put vehicle in Park or Neutral.
4. Turn all accessories off.
5. Connect a scan tool.
6. Start and run engine until engine is at normal operating temperature 165°F (74°C) on 2.2L or 185°F (85°C) on 2.4L.
7. With engine still running, use scan tool to enable CRANKSHAFT POSITION SYSTEM VARIATION LEARNING PROCEDURE.
8. Press and hold brake pedal firmly and raise engine speed to specified value of 3920 RPM, releasing throttle as soon as engine cuts out.
9. Using scan tool, verify that crankshaft variation has been learned.

PROGRAMMING THEFT DETERRENT SYSTEM COMPONENTS

If replacing a PCM with a replacement part, after programming, these modules will learn incoming fuel continue password immediately upon receipt of a password message. Once a password message is received and a password is learned, a learn procedure must be performed to change this password again. A PCM which has been previously installed in another vehicle will have learned the other vehicle's fuel continue password and will require a learn procedure after programming to learn current vehicle's password.

1. Turn ignition on, engine off.
2. Attempt to start engine, then release key to ON position (vehicle will not start).
3. Observe SECURITY telltale, after approximately 10 minutes telltale will turn off.
4. Turn ignition off and wait 5 seconds.
5. Repeat steps 1 through 4 2 more times for a total of 3 cycles in 30 minutes. Vehicle is now ready to relearn Passlock(tm) sensor data code and/or passwords on next ignition switch transition from OFF to CRANK position.
6. Start engine. Vehicle has now learned Passlock(tm) sensor data code and/or password.
7. Using scan tool, clear any DTCs if needed.

DRIVE CYCLES

See INSPECTION/MAINTENANCE SYSTEM CHECK (GASOLINE) or INSPECTION/MAINTENANCE SYSTEM CHECK (CNG) .

Diagnostic Procedures

1. Perform «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. If DTC or driveability concerns were repaired using powertrain diagnostic system check, go to step 3 . If no DTC or driveability concerns were repaired using powertrain diagnostic system check, go to next step.
2. Check for applicable Technical Service Bulletins (TSB) for software updates that may prevent Inspection/Maintenance (I/M) readiness. Perform any reprogramming or repairs indicated by TSBs. If reprogramming or repair service was required, see «INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) . If reprogramming or repair service is not required, go to next step.
3. Using scan tool, observe I/M SYSTEM STATUS display. If more than one test indicates a NO status, see «INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) . If only one test indicates a NO status, go to appropriate I/M system set procedure for indicated system.

Diagnostic Aids

I/M SYSTEM STATUS display provides an indication of when control module has completed required tests. This does not necessarily mean that test has passed, only that test has run. If diagnostics fail, a DTC will indicate failure. If a failure indication is present for a DTC associated with one of the I/M regulated systems, it may prevent other required tests from running. I/M SYSTEM STATUS information may be useful for a technician to determine if diagnostics have run when verifying repairs.

INSPECTION/MAINTENANCE SYSTEM CHECK (CNG)

Note. CNG controller supports HO2S monitoring. I/M tests that are supported by gasoline controller (PCM) are same as those in a non bi-fuel vehicle.

Description

For vehicles designed to run on fuels other than gasoline, some additional procedures may be required to set I/M System Status indicators to YES. Vehicles designed to run on both gasoline and Compressed Natural Gas (CNG) will disable certain diagnostic tests when vehicle is operating on CNG. These vehicles will require operation using gasoline for remaining tests to run. The system set procedures for gasoline vehicles can be used once vehicle is operating on gasoline.

Conditions For Updating I/M System Status

Each system requires at least one, sometimes several, diagnostic tests. Results of these tests are reported by a Diagnostic Trouble Code (DTC). System monitor is complete when either all DTCs comprising monitor have run and passed, or any one DTC comprising monitor have illuminated the Malfunction Indicator Light (MIL). Once all tests are completed, I/M System Status display will indicate YES in COMPLETED column.

For example, when HO2S Heater Test indicates YES, all oxygen sensor heaters have been diagnosed. If vehicle has four heated oxygen sensors, all four heater circuits have been diagnosed. I/M System Status will indicate NO under COMPLETED column when any required tests for that system have not run.

Following is a list of conditions that would set I/M System Status indicator to NO

1. Vehicle is new from factory and has not yet been driven through necessary drive cycles to complete tests.
2. Battery has been disconnected or discharged below operating voltage.
3. Control module power or ground has been interrupted.
4. Control module has been reprogrammed.
5. Control module DTCs have been cleared as part of a service procedure.

1. Perform powertrain diagnostic system check for alternative fuel engine controls. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. Repair any DTCs or driveability concerns that may prevent I/M System Status tests from completing. If DTCs or driveability concerns are found and repaired, go to step 3 . If no DTCs or driveability concerns are found and repaired, go to next step.
2. Check Technical Service Bulletins (TSB) for software updates that may prevent I/M readiness. Perform any reprogramming or repairs indicated by service bulletins. Go to next step.
3. Using scan tool, monitor I/M System Status display for gasoline control module (PCM). If any tests indicate NO, go to next step. If no tests indicate NO, go to step 6 .
4. Turn ignition off. Remove CNG fuse (20-amp) from underhood fuse block. Start engine and allow to idle. Using scan tool, verify engine is operating in gasoline mode. Perform necessary set procedures for I/M System Status indicators that were set to NO. Go to next step.
5. Turn ignition off. Reinstall CNG fuse. Start engine and allow it idle. Using scan tool, verify engine is operating in CNG mode. Perform necessary set procedures for I/M System Status indicators that were set to NO. After performing set procedures, system is okay.
6. Start engine and allow to idle. Using scan tool, verify engine is operating in CNG mode. Perform necessary set procedures for I/M System Status indicators that were set to NO. After performing set procedures, system is okay.

I/M System Status display provides an indication of when control module has completed required DTC tests. This does not mean test has passed, only that a decision was made. If diagnostic fails, a DTC will set to indicate failure. If a failure indication is present for a DTC associated with one of the I/M regulated systems, it may prevent other required tests from running. For example, a DTC for control circuit of relay controlling AIR pump may not be listed in Inspection/Maintenance System DTC table, because it is a continuous test. If this DTC is set, Active Tests for AIR system may not run. The I/M System Status information may be useful for a technician to determine if diagnostics have run when verifying repairs.

This procedure satisfies enable criteria necessary to execute all monitor diagnostics, and complete trips for those particular diagnostics. When all diagnostic tests have been completed, I/M System Status indicators are set to YES. Perform this test when more than one or all I/M System Status indicators are set to NO.

Ensure vehicle meets the following conditions before performing procedure

1. Barometric (BARO) pressure is more than 72 kPa.
2. Engine Coolant Temperature (ECT) is less than 84°F (29°C).
3. Intake Air Temperature (IAT) is less than 84°F (29°C).
4. Difference between Intake Air Temperature (IAT) and Engine Coolant Temperature (ECT) is 13°F (7°C) or less.
5. Battery voltage is between 9-16 volts.
6. Fuel level is 1/4-3/4 tank.

1. Perform powertrain diagnostic system check. See «INSPECTION/MAINTENANCE SYSTEM CHECK»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) . After performing powertrain diagnostic system check, go to next step.
2. Preprogram scan tool with vehicle information before ignition is turned on. Ensure vehicle meets conditions under «DESCRIPTION»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) . Turn off all accessories, such as A/C, blower fan, etc. Set vehicle parking brake. Ensure transmission is in Park for automatic transmissions and Neutral for manual transmissions. Start engine. Allow engine to idle. Allow engine to idle for 2 minutes. Go to next step.
3. Acceleration at part throttle to 55 MPH (90 km/h) with this speed maintained until engine reaches operating temperature. This may be up to 8-10 minutes depending on start-up coolant temperature. Continue operation under these conditions for an additional 6 minutes. Go to next step.
4. Reduce vehicle speed to 45 MPH (72 km/h), maintain this speed for one additional minute. Four decelerations of 25 seconds each from 45 MPH (72 km/h) while maintaining the following criteria: Throttle is closed. No brake application. No clutch actuation on M/T. No manual downshift Vehicle speed remains more than 25 MPH (40 km/h). After each deceleration period, vehicle is returned to 45 MPH (72 km/h) under part throttle acceleration and speed is maintained for 15 seconds. Go to next step.
5. Accelerate at part throttle to 45-55 MPH (75-89 km/h) and maintain this speed for 2 minutes. Decelerate to zero MPH (0 km/h). Idle engine for 2 minutes while service brake is depressed, A/T is in Drive. M/T is in Neutral with clutch pedal depressed. Go to next step.
6. Using scan tool, observe I/M System Status display. If all I/M System Status indicators update to YES, go to next step. If all I/M system status indicators do not update to YES, repeat procedure.
7. Using scan tool, observe emission related DTC portion of I/M System Status display. If scan tool indicates any emission related DTCs, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If scan tool does not indicate emission related DTCs, system is okay.

Rough road conditions may prevent some tests from running. Extreme high or low ambient temperatures may prevent tests such as Heated Oxygen Sensor (HO2S) heater and Evaporative Emission (EVAP) system from initiating. If a step is interrupted before completion, perform remaining portion of set procedure. Any portion of set procedure that requires engine at operating temperature may be repeated. This allows most diagnostics to run and remaining tests can be performed using individual system set procedure.

If vehicle has recently run, start this procedure at step 3 . This will allow tests that require the engine at operating temperature to run. Using this method allows shorter cool down periods if tests requiring a cold start do not initiate.

Scan tool can be used to monitor each I/M SYSTEM STATUS indicator during I/M complete system set procedure. When all indicators for a test step have updated to YES, testing can move on to next step even if remaining portion of test is not complete. For example, step 3 is designed to run the EVAP, secondary Air Injection (AIR), and HO2S tests. Procedure instructs technician to operate vehicle in enable conditions for 6 minutes. If all 3 tests have updated to YES within 4 minutes, it is not necessary to continue with enable conditions and testing can advance to next step.

This test should satisfy enable criteria necessary to execute I/M readiness diagnostics for the catalyst system. Test may be used to set I/M SYSTEM STATUS indicators to YES. Ensure vehicle meets requirements listed in enable criteria before performing test.

Enable Criteria

1. BARO is more than 72 kPa.
2. ECT is 167-257°F (75-125°C).
3. IAT is -4 to 176°F (-20 to 80°C).
4. Engine is in closed loop.
5. Engine has run 6-8 minutes off idle.
6. Battery voltage is 9-16 volts.

1. Perform I/M system check. See «INSPECTION/MAINTENANCE SYSTEM CHECK»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) . After performing I/M system check, go to next step.
2. Turn all accessories off. Start engine and allow to idle. Operate vehicle in the following manor: Accelerate at part throttle to 55 MPH and maintain speed for 5 minutes. Decelerate to a stop. Allow engine to idle for 2 minutes with service brake applied, A/T in drive or M/T in neutral with clutch depressed. Using scan tool, monitor I/M SYSTEM STATUS. If CATALYST SYSTEM STATUS is YES, go to step 5 . If CATALYST SYSTEM STATUS is not YES, go to next step.
3. Using scan tool, observe DTC information. If scan tool indicates any failed DTCs, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If scan tool does not indicate any failed DTCs, go to next step.
4. Using scan tool, monitor DTC P0420. Operate vehicle within code enable criteria for DTC P0420. See «DTC P0420: TWC SYSTEM - LOW EFFICIENCY (2.2L)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__dtc-p0420-twc-system-low) or «DTC P0420: TWC SYSTEM - LOW EFFICIENCY (2.4L)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__dtc-p0420-twc-system-low) under DIAGNOSTIC TESTS. Operate vehicle within code enable criteria until scan tool indicates diagnostic test has run. Using scan tool, observe I/M SYSTEM STATUS. If CATALYST SYSTEM STATUS is YES, go to next step. If CATALYST SYSTEM STATUS is not YES, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
5. Using scan tool, check for DTCs. If scan tool indicates any DTCs are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

Purpose of this test is to satisfy enable criteria necessary to execute I/M readiness diagnostics for catalyst system. Test may be used to set I/M system status indicators to YES. Ensure vehicle meets enable criteria before performing test.

This test should satisfy enable criteria necessary to execute I/M readiness diagnostics for the evaporative emission system. Test may be used to set I/M SYSTEM STATUS indicators to YES. Ensure vehicle meets requirements listed in enable criteria before performing test.

1. BARO is more than 75 kPa.
2. Fuel level is 1/4-3/4.
3. Battery voltage is 9-16 volts.
4. Test will initiate only after a cold start. PCM considers engine to be cold if ECT is 41-84°F (5-29°C), IAT is 41-84°F (5-29°C) and difference between ECT and IAT is less than 13°F (7°C).

1. Perform I/M system check. See «INSPECTION/MAINTENANCE SYSTEM CHECK»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) . After performing I/M system check, go to next step.
2. Using a scan tool, select SPECIAL FUNCTIONS. Determine if vehicle is equipped with a SERVICE BAY TEST for EVAP system. If vehicle equipped with EVAP SERVICE BAY TEST, go to next step. If vehicle is not equipped with EVAP SERVICE BAY TEST, go to step 5 .
3. Ensure vehicle is within enable criteria. Turn off all of accessories. Following directions on scan tool, perform EVAP SERVICE BAY TEST. If EVAP system passed SERVICE BAY TEST, go to step 8 . If EVAP system did not pass SERVICE BAY TEST, go to next step.
4. Observe scan tool SERVICE BAY TEST for an indication of why test did not pass, e.g., failed DTC, test aborted, etc. Refer to appropriate service information for diagnosis and repair of condition as necessary. After repair, perform «DRIVE CYCLE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__drive-cycles) .
5. Ensure vehicle is within enable criteria. Turn off all of accessories. Start engine and idle. Operate vehicle in the following manner: Acceleration at part throttle to 45 MPH. Maintain this speed until engine reaches operating temperature. This may be up to 8-10 minutes depending on start up coolant temperature. Continue operating conditions for an additional 3 minutes after engine reaches operating temperature, or until I/M SYSTEM STATUS indicator updates to YES. If EVAP SYSTEM STATUS updated to YES, go to step 8 . If EVAP SYSTEM STATUS did not update to YES, go to next step.
6. Using scan tool, observe DTC information. If scan tool indicates any failed DTCs, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If scan tool does not indicate any failed DTCs, go to next step.
7. Using scan tool, observe NOT RAN SINCE CODE CLEARED display to determine if DTCs P0440, P0442, P0446 and P1441 have run. For those DTCs that have not run, see CODE ENABLE CRITERIA under appropriate DTC under DIAGNOSTIC TESTS. Operate vehicle to meet code enable criteria until DTC(s) runs. Using scan tool, observe I/M SYSTEM STATUS display. If EVAP SYSTEM STATUS updated to YES, go to next step. If EVAP SYSTEM STATUS did not update to YES, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
8. Using scan tool, check for DTCs. If scan tool indicates any DTCs are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

Extreme high or low ambient temperatures may prevent EVAP system tests from initializing. Performing a visual inspection prior to running test may prevent having to repeat test. A loose fuel cap may cause test to abort or fail and prevent I/M system from updating. A failed or aborted test will require vehicle to cool down in order to meet enable criteria to run another test.

I/M system status does not indicate whether test has passed or failed, only that test has run. When all diagnostics for a specific system have run and passed, I/M system status will update to YES. If a test for a specific system has failed, I/M system status will update to YES, indicating a determination was made, even if all required tests have not run. When a failure occurs, DTC portion of the I/M system status display will indicate MIL is requested. I/M system status also registers number of DTCs.

First failure of a type "B" DTC does not constitute a final determination of pass or fail, and will not update I/M system status to YES. A second trip is required, and all conditions to run must be met in order for test to run again. These conditions may include a partial to complete engine cool down. I/M system status will update only when DTC fails second time, or all tests pass.

If there is an impending failure, system may require more time to run diagnostic than was allotted in set procedure. If test does not run after numerous attempts and no DTC is set, review appropriate scan tool data list and service information for an indication of why test does not complete. Some tests may abort due to changes in conditions while the is running. For example, changes in engine load, such as a cooling fan or an A/C compressor clutch turning on, may cause test to abort.

If a diagnostic test is difficult to run, observe I/M system status display while maintaining necessary enable conditions until system status updates to YES.

Purpose of this test is to satisfy enable criteria necessary to execute I/M readiness diagnostics for heated oxygen sensor/oxygen sensor system. Test may be used to set I/M system status indicators to YES. Ensure vehicle meets enable criteria before performing test.

1. ECT is more than 167°F (75°C).
2. Engine is in closed loop.
3. Engine has been running more than one minute
4. Battery voltage is 10-16 volts.

1. Perform I/M system check. See «INSPECTION/MAINTENANCE SYSTEM CHECK»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) . After performing I/M system check, go to next step.
2. Turn all accessories off. Start engine and allow to idle. Accelerate at part throttle to 45-55 MPH and maintain speed for 6 minutes or until I/M SYSTEM STATUS updates to YES. If vehicle is equipped with either a 5-or 6-speed manual transmission, operation in 4th or 5th gear respectively may be required, in order for test to run. Using scan tool, observe I/M SYSTEM STATUS. If HO2S/O2S SYSTEM STATUS updated to YES, go to step 5 . If HO2S/O2S SYSTEM STATUS did not update to YES, go to next step.
3. Using scan tool, observe DTC information. If scan tool indicates any failed DTCs, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If scan tool does not indicate any failed DTCs, go to next step.
4. Using scan tool, observe NOT RAN SINCE CODE CLEARED display to determine if DTCs P0133, P0140 and P1133 have run. For those DTCs that have not run, see CODE ENABLE CRITERIA in appropriate DTC. Operate vehicle to meet code enable criteria until DTC(s) runs. Using scan tool, observe I/M SYSTEM STATUS display. If EVAP SYSTEM STATUS updated to YES, go to next step. If EVAP SYSTEM STATUS did not update to YES, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
5. Using scan tool, check for DTCs. If scan tool indicates any DTCs are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

If status does not update, test outlined in this procedure can be repeated until I/M SYSTEM STATUS updates to YES.

I/M SYSTEM STATUS does not indicate whether test has passed or failed, only that test was run. When all diagnostics for a specific system have run and passed, I/M SYSTEM STATUS will update to YES. If a test for a specific system has failed, I/M SYSTEM STATUS will update to YES, indicating a determination was made, even if all required tests have not run. When a failure occurs, DTC portion of the I/M system status display will indicate MIL is requested. I/M system status also registers number of DTCs.

First failure of a type B DTC does not constitute a final determination of pass or fail, and will not update I/M SYSTEM STATUS to YES. A second trip is required, and all conditions to run must be met in order for test to run again. These conditions may include a partial to complete engine cool down.

I/M SYSTEM STATUS will update only when DTC fails second time, or all tests pass.

If there is an impending failure, system may require more time to run diagnostic than was allotted in set procedure. If test does not run after numerous attempts and no DTC is set, review appropriate scan tool data list and service information for an indication of why test does not complete. Some tests may abort due to changes in the conditions while test is running. For example, changes in engine load, such as a cooling fan or an A/C compressor clutch turning on, may cause test to abort.

If a diagnostic test is difficult to run, observe I/M SYSTEM STATUS display while maintaining necessary enable conditions until system status updates to YES.

This test is to satisfy enable criteria to execute I/M readiness diagnostics for Oxygen Sensor (O2S) and Heated Oxygen Sensor (HO2S) system. Test may be used to set I/M System Status to YES. Ensure vehicle meets requirements listed in CONDITIONS FOR RUNNING before performing this test. Failure to meet necessary requirements may produce inaccurate test results.

Conditions For Running

1. Engine must be operating on CNG.
2. Engine Coolant Temperature (ECT) is more than 160°F (70°C).
3. Engine must be running in closed loop fuel control
4. Engine must have been running for more than 2 minutes.

1. If inspection/maintenance system check (CNG) has been performed, go to next step. If inspection/maintenance system check (CNG) has not been performed, go to «INSPECTION/MAINTENANCE SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__inspectionmaintenance-system-check-cng) . After performing inspection/maintenance system check (CNG), go to next step.
2. Ensure vehicle is within «CONDITIONS FOR RUNNING»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__conditions-for-running) . Turn off all accessories. Start engine and allow to idle. Road test vehicle. For this test to run, accelerate at part throttle to 45-55 MPH. Maintain this speed for 6 minutes or until I/M System Status updates to YES. Manual transmission equipped vehicles (5 or 6 speed), may require operation in 4th or 5th gear respectively, for this test to run. Using scan tool, review I/M System Status display. If HO2S/O2S System Status updates to YES, go to step 5 . If HO2S/O2S System Status does not update to YES, go to next step.
3. Using scan tool, monitor DTC Information for both CNG (AF ECU) and gasoline control modules (PCM). If scan tool indicates any failed DTC, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. If scan tool does not indicate any failed DTCs, go to next step.
4. Using scan tool, monitor NOT RAN SINCE CODE CLEARED display. Determine which HO2S/O2S DTCs required for a YES status, have not run. Enter DTC number in SPECIFIC DTC menu of scan tool. Operate vehicle within «CONDITIONS FOR RUNNING»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__conditions-for-running) . Repeat until scan tool indicates diagnostic test has run. Repeat for any additional required DTCs that have not run. Using scan tool, observe I/M System Status display. If HO2S/O2S System Status updates to YES, go to next step. If HO2S/O2S System Status does not update to YES, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
5. Using scan tool, monitor Emission Related DTC portion of I/M System Status display. If scan tool indicates any Emission Related DTCs are set, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. If scan tool does not indicate any Emission Related DTCs are set, system is okay.

If status does not update, test outlined in this procedure can be repeated until I/M System Status updates to YES. I/M System Status does not indicate if test has passed or failed, only that a decision was made. When all diagnostics for a specific system have run and passed, I/M System Status will update to YES. If test for a specific system has failed, I/M System Status will update to YES, indicating a determination was made, even if all required tests have not run. When a failure occurs, Emission Related DTC portion of I/M System Status display will indicate Malfunction Indicator Light (MIL) is requested. I/M System Status also registers number of Diagnostic Trouble Codes (DTCs).

First failure of a type "B" DTC does not constitute a final determination of pass or fail, and will not update I/M System Status to YES. A second trip is required, and all conditions to run must be met for test to run again. These conditions may include a partial to complete engine cool down. I/M System Status will update only when an emission related DTC fails for a second time, or when all tests pass.

If there is an impending failure, system may require more time to run diagnostic than allotted in set procedure. If test does not run after numerous attempts and no DTCs are set, review appropriate scan tool data list and service information for an indication of why test does not complete. Some tests may abort due to changes in conditions while the test is running. For example, changes in engine load, such as a cooling fan or an A/C compressor clutch turning ON, may cause test to abort. If diagnostic test is difficult to run, observe I/M System Status display while maintaining necessary enable conditions until system status updates to YES.

Purpose of this test is to satisfy enable criteria necessary to execute I/M readiness diagnostics for heated oxygen sensor heater system. Test may be used to set I/M system status indicators to YES. Ensure vehicle meets enable criteria before performing test.

1. ECT is less than 104°F (40°C).
2. ECT is less than 104°F (40°C).
3. Difference between ECT and IAT is less than 13°F (7°C).
4. Battery voltage is 11.6-16.0 volts.

1. Perform I/M system check. See «INSPECTION/MAINTENANCE SYSTEM CHECK»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) . After performing I/M system check, go to next step.
2. Preprogram scan tool with vehicle information before ignition is turned on. Ensure vehicle is within enable criteria. Set vehicle parking brake. Verify transmission is in Park for A/T and Neutral for M/T. Turn off all of accessories. Start engine and allow it to idle for 2 minutes or until I/M SYSTEM STATUS indicator updates to YES. If HO2S HEATER SYSTEM STATUS updates to YES, go to step 5 . If HO2S HEATER SYSTEM STATUS does not update to YES, go to next step.
3. Using scan tool, observe DTC information. If scan tool indicates any failed DTCs, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If scan tool does not indicate any failed DTCs, go to next step.
4. Using scan tool, monitor DTC P0141. Operate vehicle within code enable criteria for DTC P0141. See «DTC P0141: HO2S2 HEATER CIRCUIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__dtc-p0141-ho2s2-heater-circuit) under DIAGNOSTIC TESTS. Operate vehicle within code enable criteria until scan tool indicates diagnostic test has run. Using scan tool, observe I/M SYSTEM STATUS. If CATALYST SYSTEM STATUS is YES, go to next step. If CATALYST SYSTEM STATUS is not YES, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
5. Using scan tool, check for DTCs. If scan tool indicates any DTCs are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

HO2S heater tests will normally run within 2 minutes allotted in procedure. If there is an indeterminate condition, test may take up to 8 minutes on some vehicles before a decision of pass or fail is made. If test does not update within allotted period of time, continue operation within enable conditions until test updates to YES. If test does not update to YES, it may have failed or aborted due to loss of enabling conditions. Extremely high ambient temperatures may prevent HO2S heater test from initiating.

I/M SYSTEM STATUS does not indicate whether test has passed or failed, only that test was run. When all diagnostics for a specific system have run and passed, I/M SYSTEM STATUS will update to YES. If a test for a specific system has failed, I/M SYSTEM STATUS will update to YES, indicating a determination was made, even if all required tests have not run. When a failure occurs, DTC portion of the I/M system status display will indicate MIL is requested. I/M system status also registers number of DTCs.

First failure of a type "B" DTC does not constitute a final determination of pass or fail, and will not update I/M SYSTEM STATUS to YES. A second trip is required, and all conditions to run must be met in order for test to run again. These conditions may include a partial to complete engine cool down.

If a diagnostic test is difficult to run, observe I/M SYSTEM STATUS display while maintaining necessary enable conditions until system status updates to YES.

SUMMARY

If no DTC(s) are present and driveability symptoms exist proceed to appropriate TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.).

DIAGNOSTIC TROUBLE CODE DEFINITIONS

Note. Use of Tech 2 or generic OBD II scan tool is required to retrieve DTCs. Refer to user reference manual supplied with scan tool.

DIAGNOSTIC TROUBLE CODE DEFINITIONS

MIL INOPERATIVE (GASOLINE)

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Inspect fuse that supplies voltage to MIL (BCM/CLU fuse on "J" body and IPC/BFC ACC fuse on "N" body). If fuse is open, go to step 10 . If fuse is okay, go to next step.
3. Turn ignition off. Disconnect PCM. Turn ignition on, engine off. Connect fused jumper wire (3-amp) between MIL control circuit (Brown/White wire) and ground. See WIRING DIAGRAMS article. Observe MIL. If MIL illuminated, go to step 9 . If MIL is not illuminated, go to next step.
4. If fuse in jumper wire opened, go to step 11 . If fuse in jumper wire did not open, go to next step.
5. Remove Instrument Panel Cluster (IPC). Check MIL control circuit (Brown/White wire) for open between PCM and IPC. If problem was found, repair as necessary. After repairs, go to step 14 . If problem was not found, go to next step.
6. Using test light connected to ground, probe MIL ignition supply voltage circuit (Pink wire on "J" body and Purple wire on "N" body) at IPC harness connector. See WIRING DIAGRAMS article. If test light is on, go to step 8 . If test light is off, go to next step.
7. Repair open in MIL ignition supply voltage circuit. See WIRING DIAGRAMS article. After repairs, go to step 14 .
8. Check IPC connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 14 . If problem was not found, go to step 12 .
9. Check PCM connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 14 . If problem was not found, go to step 13 .
10. Repair short to ground in MIL ignition supply voltage circuit (Pink wire on "J" body and Purple wire on "N" body). See WIRING DIAGRAMS article. After repairs, go to step 14 .
11. Repair short to voltage in MIL control circuit (Pink wire on "J" body and Purple wire on "N" body). See WIRING DIAGRAMS article. After repairs, go to step 14 .
12. Replace IPC. See appropriate ANALOG INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. After repairs, go to step 14 .
13. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
14. Operate system to verify repair.

MIL INOPERATIVE (CNG)

1. If you have been sent to this procedure from another diagnostic procedure, go to next step. If you have not been sent to this procedure from another diagnostic procedure, perform alternative fuels engine controls diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Turn ignition on. If Malfunction Indicator Light (MIL) is illuminated continuously, go to next step. If MIL is not illuminated continuously, go to step 5.
3. Using scan tool, communicate with Alternate Fuel Engine Control Unit (AF ECU) and command MIL off. If MIL is illuminated, go to «MIL ON STEADY (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__mil-on-steady-cng). If MIL is not illuminated, go to next step.
4. MIL malfunction is not present at this time. If a MIL operational symptom is still present, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. If a MIL operational symptom is no longer present, problem may be intermittent. See «INTERMITTENT TROUBLE CODE DETERMINATION»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__intermittent-trouble-code-determination) under ON-BOARD DIAGNOSTICS in SELF-DIAGNOSTIC SYSTEM.
5. Crank engine for at least 10 seconds. If engine starts and runs, go to next step. If engine fails to start and run, go to step 9.
6. Observe operation of other Instrument Panel Cluster (IPC) gauges and/or indicator lights. If all IPC indicators and gauges (except MIL) operate properly, go to next step. If all IPC indicators and gauges do not operate properly, go to step 13.
7. Turn ignition on. Using scan tool, select ALT. FUELS DATA LIST and observe GASOLINE MIL COMMAND data parameter. If PCM is commanding MIL ON, go to next step. If PCM is not commanding MIL ON, go to step 11.
8. Turn ignition off. Disconnect AF ECU connectors. AF ECU is located behind left front fascia, below headlight. (Scheme 2) Turn ignition on. Connect a fused jumper between AF ECU Blue connector C001 terminal No. 2 (Brown/White wire) and ground. (Scheme 3) If MIL illuminates, go to step 14. If MIL does not illuminate, go to step 10. If fused jumper blows, repair short to voltage in Brown/White wire between AF ECU and IPC connector C1 terminal "D". (Scheme 4)
9. Fault is in gasoline control (PCM) system. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After repairing gasoline control system, go to step 17.
10. Check for open in Brown/White wire between AF ECU Blue connector C001 terminal No. 2 and IPC connector C1 terminal "D". Repair as necessary. After repairs, go to step 17. If circuit is okay, go to step 13.
11. Check for open or short to voltage in Brown wire between AF ECU Blue connector C001 terminal No. 22 and PCM connector C2 terminal No. 46. (Scheme 3)and (Scheme 5). Check for short to voltage in Brown/White wire between AF ECU Blue connector C001 terminal No. 2 and IPC connector C1 terminal "D". (Scheme 4) Repair as necessary. After repairs, go to step 17. If circuit is okay, go to next step.
12. Check for poor connections at PCM. Repair as necessary. After repairs, go to step 17. If connections are okay, go to step 15.
13. Replace IPC. See INSTRUMENT CLUSTER under REMOVAL & INSTALLATION in ANALOG INSTRUMENT PANELS - CAVALIER & SUNFIRE article. After repairs, go to step 17.
14. Check for poor connections at AF ECU. Repair as necessary. After repairs, go to step 17. If connections are okay, go to step 16.
15. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) PCM with correct vehicle software and calibration. See «POWERTRAIN CONTROL MODULE REPROGRAMMING»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-control-module-reprogramming) under PROGRAMMING. To perform CKP variation learn procedure, a switch-over to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switch-over. Perform CKP system variation learn procedure. See «CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__crankshaft-position-sensor-system-variation-learn) under PROGRAMMING. After performing repairs and procedures, go to step 17.
16. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to next step.
17. Remove all test equipment except scan tool. Reconnect any disconnected components. Using scan tool, clear DTCs from AF ECU and PCM. Turn ignition off and wait 30 seconds. Start engine and operate vehicle. Monitor FIL and MIL operation. Observe vehicle performance and driveability. After operating vehicle check for DTCs in AF ECU and PCM. If vehicle operates on CNG with normal driveability, no FIL/MIL illumination and no set DTCs, system is okay. If vehicle does not operate on CNG with normal driveability, or FIL/MIL are illuminated or DTCs are set, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM.

Scheme 2

Scheme 3

Identifying Instrument Panel Cluster Connector Terminals. Scheme 4

Scheme 5

MIL ON STEADY (GASOLINE)

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition off. Disconnect PCM. Turn ignition on, engine off. Observe MIL. If MIL is illuminated, go to next step. If MIL is not illuminated, go to step 5 .
3. Remove Instrument Panel Cluster (IPC). Check MIL control circuit (Brown/White wire) for short to ground between PCM and IPC. See WIRING DIAGRAMS article. If problem was found, repair as necessary. After repairs, go to step 6 . If problem was not found, go to next step.
4. Replace IPC. See appropriate ANALOG INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. After repairs, go to step 6 .
5. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
6. Operate system to verify repair.

MIL ON STEADY (CNG)

1. If you have been sent to this procedure from another diagnostic procedure, go to next step. If you have not been sent to this procedure from another diagnostic procedure, perform alternative fuels engine controls diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Turn ignition on. If Malfunction Indicator Light (MIL) is illuminated continuously, go to next step. If MIL is not illuminated, go to «MIL INOPERATIVE (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__mil-inoperative-cng).
3. Using scan tool, communicate with Alternate Fuel Engine Control Unit (AF ECU) and command MIL off. If MIL is illuminated, go to step 5. If MIL is not illuminated, go to next step.
4. MIL malfunction is not present at this time. If a MIL operational symptom is still present, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. If a MIL operational symptom is no longer present, problem may be intermittent. See «INTERMITTENT TROUBLE CODE DETERMINATION»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__intermittent-trouble-code-determination) under ON-BOARD DIAGNOSTICS in SELF-DIAGNOSTIC SYSTEM.
5. Using scan tool, select ALT. FUELS DATA LIST and observe GASOLINE MIL COMMAND data parameter while the MIL is commanded OFF. If a gasoline MIL command request present, go to step 7. If a gasoline MIL command request is not present, go to next step.
6. Check for short to ground in Brown/White wire between AF ECU Blue connector C001 terminal No. 2 and IPC connector C1 terminal "D". (Scheme 3)and (Scheme 4). Check for internally shorted Instrument Panel Cluster (IPC). Repair as necessary. After repairs, go to step 9. If circuit is okay, go to step 8.
7. Check for short to ground in Brown wire between AF ECU Blue connector C001 terminal No. 22 and PCM connector C2 terminal No. 46. (Scheme 3)and (Scheme 5). Repair as necessary. After repairs, go to step 9. If circuit is okay, go to next step.
8. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to next step.
9. Remove all test equipment except scan tool. Reconnect any disconnected components. Using scan tool, clear DTCs from AF ECU and PCM. Turn ignition off and wait 30 seconds. Start engine and operate vehicle. Monitor FIL and MIL operation. Observe vehicle performance and driveability. After operating vehicle check for DTCs in AF ECU and PCM. If vehicle operates on CNG with normal driveability, no FIL/MIL illumination and no set DTCs, system is okay. If vehicle does not operate on CNG with normal driveability, or FIL/MIL are illuminated or DTCs are set, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM.

DIAGNOSTIC TESTS

Note. Before clearing DTCs, perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE) or POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG) under SELF-DIAGNOSTIC SYSTEM. Record FREEZE FRAME and FAILURE RECORDS for reference during testing. Data will be erased when DTCs are cleared.

DTC P0105: MAP/TP SENSOR PERFORMANCE/RANGE (GASOLINE)

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM supplies a 5-volt reference signal and a ground circuit to both the MAP sensor and TP sensor. MAP sensor returns a signal to PCM relative to intake manifold pressure, and TP sensor returns a signal to PCM relative to throttle plate opening.

PCM can determine if sensors are out of range by comparing sensor values to expected limits predetermined by PCM during all modes of operation. DTC P0105 will set if MAP sensor or TP sensor are out of an expected range as determined by engine calibration.

Code Enable Criteria

1. DTCs P0107, P0108, P0117, P0118, P0122, P0123, P0125, P0128, P0130, P0131, P0132, P0171, P0172, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0336, P0440, P0442, P0446, P0452, P0453, P0502, P0506, P0507 or P1441 is not set.
2. Engine run time is more than 40 seconds.
3. Engine speed is between 900-6375 RPM for M/T, 600-6375 RPM for A/T.
4. Torque Converter Clutch (TCC) is stable to within 2.5 percent.
5. Engine speed is stable within 50 RPM.
6. IAC valve is stable within 5 counts.
7. Conditions are present for 1.5 seconds.

DTC sets when MAP sensor or TP sensor is out of an expected range defined by engine calibration for 14 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Observe TP sensor voltage on scan tool. If scan tool displays TP voltage less than 0.90 volt when throttle is fully closed, go to next step. If scan tool does not display TP voltage less than 0.90 volt, go to step 4.
3. Select TP ANGLE parameter on scan tool. Monitor scan tool while slowly depressing accelerator pedal to floor, then slowly release pedal. Repeat procedure several times. If TP angle value increases steadily when accelerator pedal is depressed to more than 98 percent and decrease steadily, returning to less than one percent when pedal is released, go to step 5. If TP angle value does not increases steadily when accelerator pedal is depressed to more than 98 percent or does not decrease steadily, returning to less than one percent when pedal is released, go to step 17.
4. Check throttle body for binding linkage or damaged linkage. If problem was found, repair as necessary. After repairs, go to step 34. If problem was not found, go to step 17.
5. Compare BARO reading with known good vehicle. BARO value should be within one in. Hg of other vehicle. If BARO reading is normal for your altitude, go to next step. If BARO reading is not normal for your altitude, go to step 9.
6. Start engine while watching MAP sensor value with scan tool. If MAP sensor value changes while starting engine, go to next step. If MAP sensor value does not change while starting engine, go to step 8.
7. With engine running, snap throttle while watching MAP sensor display on scan tool. If MAP sensor value changes rapidly when throttle position changes, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l). If MAP sensor value does not change rapidly when throttle position changes, go to next step.
8. Turn ignition off. Remove MAP sensor from vacuum source. (Scheme 6)or (Scheme 7). Inspect port for vacuum restrictions and vacuum leaks. If problem was found, repair as necessary. After repairs, go to step 34. If problem was not found, go to next step.
9. Turn ignition off. Disconnect MAP sensor electrical connector. Turn ignition on. Observe MAP sensor voltage on scan tool. If scan tool indicates near zero volts, go to next step. If scan tool does not indicate near zero volts, go to step 12.
10. Using test light connected to ground, probe MAP sensor connector terminal "C" (Brown wire on "N" body or Gray wire on "J" body). (Scheme 8) If test light is on, go to next step. If test light is off, go to step 14.
11. Connect fused jumper wire (3-amp) between MAP sensor connector terminals "C" (Brown wire on "N" body or Gray wire on "J" body) and "B" (Light Green wire). If scan tool indicates voltage near 5 volts, go to step 13. If scan tool does not indicate voltage near 5 volts, go to step 15.
12. Check Light Green wire between MAP sensor and PCM for short to voltage. If problem was found, repair as necessary. After repairs, go to step 34. If problem was not found, go to step 30.
13. Using test light connected to battery voltage, probe MAP sensor connector terminal "A" (Orange/Black wire on "N" body or Black/White wire on "J" body). If test light is on, go to step 28. If test light is off, go to step 16.
14. Check Brown wire on "N" body or Gray wire on "J" body between MAP sensor and PCM for high resistance. If problem was found, repair as necessary. After repairs, go to step 34. If problem was not found, go to step 30.
15. Check Light Green wire between MAP sensor and PCM for high resistance. If problem was found, repair as necessary. After repairs, go to step 34. If problem was not found, go to step 30.
16. Check Orange/Black wire on "N" body or Black/White wire on "J" body between MAP sensor and PCM for high resistance. If problem was found, repair as necessary. After repairs, go to step 34. If problem was not found, go to step 30.
17. Turn ignition off. Disconnect TP sensor electrical connector. (Scheme 6)or (Scheme 7). Turn ignition on. Observe TP sensor voltage on scan tool. If scan tool indicates voltage is near zero volt, go to next step. If scan tool does not indicate voltage is near zero volt, go to step 21.
18. Using test light connected to ground, probe TP sensor connector terminal "A" (Gray wire on "J" body or Gray/Black wire on "N" body). (Scheme 9) If test light is on, go to next step. If test light is off, go to step 23.
19. Using DVOM, measure voltage between TP sensor connector terminal "A" (Gray wire on "J" body or Gray/Black wire on "N" body) and ground. If voltage is more than 5.2 volts, go to step 24. If voltage is not more than 5.2 volts, go to next step.
20. Connect fused jumper wire (3-amp) between TP sensor connector terminals "A" (Gray wire on "J" body or Gray/Black wire on "N" body) and "C" (Dark Blue wire). If scan tool indicates voltage is near 5 volts, go to step 22. If scan tool does not indicate voltage is near 5 volts, go to step 25.
21. Check Dark Blue wire between TP sensor and PCM for short to voltage. If problem was found, repair as necessary. After repairs, go to step 34. If problem was not found, go to step 30.
22. Using test light connected to battery voltage, probe TP sensor connector "B" (Black wire) at TP sensor connector. If test light is on, go to step 29. If test light is off, go to step 26.
23. Check Gray wire on "J" body or Gray/Black wire on "N" body between TP sensor and PCM for high resistance. If problem was found, repair as necessary. After repairs, go to step 34. If problem was not found, go to step 30.
24. Check Gray wire on "J" body or Gray/Black wire on "N" body between TP sensor and PCM for short to voltage. If problem was found, repair as necessary. After repairs, go to step 34. If problem was not found, go to step 27.
25. Check Dark Blue wire between TP sensor and PCM for high resistance. If problem was found, repair as necessary. After repairs, go to step 34. If problem was not found, go to step 30.
26. Check TP sensor Black wire for high resistance. If problem was found, repair as necessary. After repairs, go to step 34. If problem was not found, go to step 30.
27. Check A/C high side pressure sensor connector terminal "B" (Gray wire) and Fuel Tank Pressure (FTP) sensor connector terminal "C" (Gray wire) for short to voltage. (Scheme 8)and (Scheme 9). If problem was found, repair as necessary. After repairs, go to step 34. If problem was not found, go to step 30.
28. Check MAP sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 34. If problem was not found, go to step 31.
29. Check TP sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 34. If problem was not found, go to step 32.
30. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 34. If problem was not found, go to step 33.
31. Replace MAP sensor. After repairs, go to step 34.
32. Replace TP sensor. See THROTTLE POSITION SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 35.
33. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 35.
34. Using scan tool, perform FUEL TRIM RESET procedure. After repairs, go to step 36.
35. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, system is okay.
36. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

1. If a DTC P0105 cannot be duplicated, information included in FREEZE FRAME/FAILURE RECORDS data can be useful. Use scan tool DTC information data in order to determine status of DTC.
2. A DTC P0105 may set due to any condition that may cause an unreasonably high or low MAP value including incorrect cam timing, restricted exhaust, worn piston rings or low fuel pressure.
3. A TP sensor that is stuck may attempt to auto zero everytime engine runs. If this happens, TP percentage will be zero percent and TP voltage will be high.
4. MAP sensor needs a dedicated vacuum source. Check MAP sensor and MAP sensor vacuum source for a vacuum leak.

Scheme 6

Scheme 7

Scheme 8

Scheme 9

Powertrain Control Module (PCM) supplies 5 volts on Throttle Position (TP) and Manifold Absolute Pressure (MAP) sensor reference voltage circuits. PCM also supplies a ground circuit to TP and MAP sensors. When throttle is depressed, TP signal voltage rises to approximately 5 volts. As throttle is released, TP signal voltage drops to around 0.6 volt. PCM and the Alternate Fuel Engine Control Unit (AF ECU) monitor TP signal circuit voltage and determine angle (or opening) of throttle plate.

When manifold vacuum is low, MAP signal voltage to approximately 4.5 volts. As manifold vacuum increases, MAP signal voltage drops to around one volt. PCM and AF ECU monitor MAP signal circuit voltage and determine vacuum within intake manifold.

Certain vehicle models will also use MAP sensor to determine barometric pressure when ignition switch is turned ON and engine is not running. This BARO reading may also be updated whenever engine is operated at wide open throttle.

For DTC to run, the following conditions must be met

1. Engine is operating on alternative fuel (CNG).
2. Engine has been running for more than 5 seconds.
3. No AF ECU DTCs are set.
4. DTCs P1215, P1432 and P1433 may be set.
5. TP sensor angle is less than 70 percent.

DTC will set when AF ECU detects MAP sensor pressure changes less than 6 kPa when TP sensor angle changes by more than 20 percent.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, establish communication with AF ECU. Observe and record MAP sensor kPa display. If MAP sensor kPa reading is more than 75 kPa at altitude or 95 kPa at sea level, go to next step. If MAP sensor kPa readings less than 75 kPa at altitude or 95 kPa at sea level, go to step 7.
3. Remove vacuum line from MAP sensor. (Scheme 6) Connect Hand Vacuum Pump (J 23738-A) to MAP sensor. Slowly apply vacuum one in. Hg at a time. Monitor MAP sensor kPa display on scan tool. Each one inch of vacuum should result in a 3 to 4 kPa drop in MAP sensor kPa reading. Observe MAP sensor kPa reading for a skip or jump while increasing vacuum up to 20 in. Hg. If MAP sensor kPa reading skips or jumps, go to step 7. If MAP sensor kPa reading does not skip or jump, go to next step.
4. Monitor MAP sensor kPa reading with 20 in. Hg of vacuum applied. If MAP sensor kPa reading is less than 34 kPa, go to next step. If MAP sensor kPa reading is more than 34 kPa, go to step 7.
5. Disconnect MAP sensor from hand vacuum pump. If MAP sensor kPa reading is more than 75 kPa at altitude or 95 kPa at sea level, go to next step. If MAP sensor kPa readings less than 75 kPa at altitude or 95 kPa at sea level, go to step 7.
6. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
7. Check for poor connections at MAP sensor. Check open or high resistance in Black/White wire between MAP sensor connector terminal "A" and PCM connector C2 terminal No. 14. (Scheme 5) If problem is found, go to next step. If connections and circuit are okay, go to step 9.
8. Repair connections or circuit as necessary. After repairs, go to step 10.
9. Replace MAP sensor. See MANIFOLD ABSOLUTE PRESSURE SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
10. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

DTC P0107: MAP SENSOR CIRCUIT - LOW VOLTAGE (GASOLINE)

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM supplies 5 volts to MAP sensor on 5-volt reference circuit. PCM also provides a ground on low reference circuit. MAP sensor provides a signal to PCM on signal circuit which is relative to pressure changes in manifold. PCM should detect a low signal voltage at a low MAP, such as during idle or deceleration. PCM should detect a high signal voltage at a high MAP, such as ignition on, with engine off, or at Wide Open Throttle (WOT). Certain models will also use MAP sensor in order to determine Barometric (BARO) pressure. This occurs when ignition is turned on, with engine off. BARO reading may also be updated whenever engine is operated at WOT. PCM monitors MAP sensor signal for voltage outside of normal range.

1. DTCs P0122 or P0123 are not set.
2. Engine speed is less than 1000 RPM.
3. Engine speed is more than 1000 RPM, and throttle position is more than 15 percent.

DTC sets when MAP sensor voltage is less than 0.2 volt for at least 6.25 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, observe MAP sensor voltage. If scan tool indicates voltage is less than 0.2 volt, go to step 4. If scan tool does not indicate voltage is less than 0.2 volt, go to next step.
3. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or as close to FREEZE FRAME/FAILURE RECORDS data that you observed. If DTC fails this ignition cycle, go to next step. If DTC does not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Disconnect MAP sensor electrical connector. (Scheme 6)or (Scheme 7). Turn ignition on, engine off. Measure voltage between MAP sensor connector terminal "C" (Gray wire on "J" body and Brown wire on "N" body) and ground. (Scheme 8) If voltage measures near 5 volts, go to next step. If voltage does not measure near 5 volts, go to step 6.
5. Connect fused jumper wire (3-amp) between MAP sensor connector terminals "C" (Gray wire on "J" body and Brown wire on "N" body) and "B" (Light Green wire). If scan tool indicates voltage is near 5 volts, go to step 8. If scan tool does not indicate voltage near 5 volts, go to step 7.
6. Check Gray wire on "J" body and Brown wire on "N" body between MAP sensor and PCM for short to ground or open. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 9.
7. Check Light Green wire between MAP sensor and PCM for short to ground or open. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 9.
8. Check MAP sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 10.
9. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 11.
10. Replace MAP sensor. After repairs, go to step 12.
11. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 13.
12. Using scan tool, perform FUEL TRIM RESET procedure. After performing procedure, go to next step.
13. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
14. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

PCM uses a single 5-volt reference output to supply power to all engine control components. If a component's 5-volt reference circuit is shorted to ground or shorted to voltage, other 5-volt reference circuits may be affected.

Inspect MAP sensor vacuum source for leaks, restrictions, or poor connections.

Powertrain Control Module (PCM) supplies 5-volt reference and ground to Manifold Absolute Pressure (MAP) sensor. When manifold vacuum is low, MAP signal voltage rises to near 4.5 volts. As manifold vacuum increases, MAP signal voltage drops to around one volt. PCM and Alternate Fuel Engine Control Unit (AF ECU) monitor MAP signal circuit voltage and determine vacuum within intake manifold. Certain vehicle models will also use MAP sensor to determine barometric pressure when ignition is on and engine is off. This BARO reading may also be updated when engine is operated at wide open throttle.

For DTC to run, the following conditions must be met

1. Engine is operating on alternative fuel.
2. Engine speed is more than 500 RPM.
3. DTCs P0121, P0122, P0123 are not set.
4. Throttle Position (TP) angle is less than 4 percent when engine speed is less than 1200 RPM or TP angle is more than 20 percent when engine speed is more than 1300 RPM.

DTC will set when AF ECU detects a MAP sensor signal voltage of less than 0.098 volts for at least 4 continuous seconds. When DTC is set, AF ECU will switch to gasoline fuel operation. AF ECU will not attempt alternative fuel operation until next key cycle.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Using scan tool, communicate PCM. Observe MAP sensor voltage. If MAP sensor voltage is less than 0.2 volt, go to step 5. If MAP sensor voltage is more than 0.2 volt, go to next step.
3. Using scan tool, communicate with AF ECU. Observe MAP sensor voltage. If MAP sensor data parameter indicates MAP voltage is less than 0.09 volt, go to step 13. If MAP sensor voltage is more than 0.09 volt, go to next step.
4. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
5. Monitor MAP sensor voltage on scan tool. Disconnect MAP sensor connector. Connect a fused jumper between MAP sensor connector terminals "B" (Light Green wire) and "C" (Gray wire). If MAP sensor voltage is more than 4.8 volts, go to step 11. If MAP sensor voltage is less than 4.8 volts, go to next step.
6. Remove fused jumper. Using DVOM, measure voltage between ground and MAP sensor connector terminal "C" (Gray wire). If voltage is less than 4.8 volts, go to step 9. If voltage is more than 4.8 volts, go to next step.
7. Check for open or high resistance in Light Green wire between MAP sensor connector terminal "B" and PCM connector C1 terminal No. 62. (Scheme 5) Check for poor connections at MAP sensor and PCM. Repair circuit or connections as necessary. After repairs, go to step 14. If circuit is okay, go to next step.
8. Disconnect AF ECU Blue connector. AF ECU is located behind left front fascia, below headlight. (Scheme 2) Check for short to ground or sensor ground circuit in Light Green wire between MAP sensor connector terminal "B" and PCM connector C1 terminal No. 62. Repair as necessary. After repairs, go to step 14. If circuit is okay, go to step 12.
9. Check for open or high resistance in Gray wire between MAP sensor connector terminal "C" and PCM connector C2 terminal No. 35. Check for poor connections at MAP sensor and PCM. Repair circuit or connector as necessary. After repairs, go to step 14. If wiring and connectors are okay, go to next step.
10. Check for short to ground in all 5-volt reference circuits from PCM. See WIRING DIAGRAMS article. Some 5-volt reference circuits are shared within PCM. Disconnect AF ECU connector containing 5-volt reference circuit to determine if AF ECU is cause of short. Disconnect all other sensors connected to PCM 5-volt reference circuits to determine if a sensor is cause of short. Repair or replace components or circuits as necessary. After repairs, go to step 14. If components and circuits are okay, go to step 12.
11. Replace MAP sensor. See MANIFOLD ABSOLUTE PRESSURE SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 14.
12. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) PCM with correct vehicle software and calibration. See «POWERTRAIN CONTROL MODULE REPROGRAMMING»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-control-module-reprogramming) under PROGRAMMING. To perform CKP variation learn procedure, a switch-over to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switch-over. Perform CKP system variation learn procedure. See «CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__crankshaft-position-sensor-system-variation-learn) under PROGRAMMING. After performing repairs and procedures, go to step 14.
13. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to next step.
14. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

DTC P0108: MAP SENSOR CIRCUIT - HIGH VOLTAGE (GASOLINE)

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM supplies 5 volts to MAP sensor on 5-volt reference circuit. PCM also provides a ground on low reference circuit. MAP sensor provides a signal to PCM on signal circuit which is relative to pressure changes in manifold. PCM should detect a low signal voltage at a low MAP, such as during an idle or a deceleration. PCM should detect a high signal voltage at a high MAP, such as ignition on, with engine off, or at a Wide Open Throttle (WOT). Certain models will also use MAP sensor in order to determine Barometric (BARO) pressure. This occurs when ignition is turned on, with engine off. BARO reading may also be updated whenever engine is operated at WOT. PCM monitors MAP sensor signal for voltage outside of normal range.

1. DTCs P0122 or P0123 are not set.
2. Throttle position is less than 12 percent.
3. Vehicle speed is less than one MPH (2 km/h).
4. Engine run time is more than 20 to 40 seconds.

DTC sets when MAP sensor voltage is more than 3.8 volts for at least 1.25 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Start engine. Let engine idle. If scan tool indicates MAP sensor voltage is more than 3.8 volts, go to step 4. If scan tool does not indicate MAP sensor voltage is more than 3.8 volts, go to next step.
3. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or as close to FREEZE FRAME/FAILURE RECORDS data that you observed. If DTC fails this ignition cycle, go to next step. If DTC does not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Disconnect MAP sensor connector. (Scheme 6)or (Scheme 7). Turn ignition on, engine off. If scan tool indicates MAP sensor voltage is less than 0.2 volt, go to next step. If scan tool does not indicate MAP sensor voltage is less than 0.2 volt, go to step 7.
5. Measure voltage between MAP sensor connector terminals "A" (Black/White wire on "J" body and Orange/Black wire on "N" body) and "C" (Gray wire on "J" body and Brown wire on "N" body). (Scheme 8) If voltage is 4.7-5.2 volts, go to step 10. If voltage is not 4.7-5.2 volts, go to next step.
6. If voltage is more than 5.2 volts, go to step 9. If voltage is not more than 5.2 volts, go to step 8.
7. Check Light Green wire between MAP sensor and PCM for short to voltage. If problem was found, repair as necessary. After repairs, go to step 14. If problem was not found, go to step 11.
8. Check Black/White wire on "J" body and Orange/Black wire on "N" body between MAP sensor and PCM for open. If problem was found, repair as necessary. After repairs, go to step 14. If problem was not found, go to step 11.
9. Check Gray wire on "J" body and Brown wire on "N" body between MAP sensor and PCM for short to voltage. If problem was found, repair as necessary. After repairs, go to step 14. If problem was not found, go to step 11.
10. Check MAP sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 14. If problem was not found, go to step 12.
11. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 14. If problem was not found, go to step 13.
12. Replace MAP sensor. After repairs, go to step 14.
13. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 15.
14. Using scan tool, perform FUEL TRIM RESET procedure. After performing procedure, go to next step.
15. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
16. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

DTC may set when attempting to start a vehicle that is out of fuel.

PCM uses a single 5-volt reference output to supply power to all of engine control components. If a component's 5-volt reference circuit is shorted to ground or shorted to voltage, other 5-volt reference circuits may be affected.

Inspect MAP sensor vacuum source for leaks, restrictions, or poor connections.

DTC may set as the result of a misfire.

Powertrain Control Module (PCM) supplies 5-volt reference and ground to Manifold Absolute Pressure (MAP) sensor. When manifold vacuum is low, MAP signal voltage rises to near 4.5 volts. As manifold vacuum increases, MAP signal voltage drops to around one volt. PCM and Alternate Fuel Engine Control Unit (AF ECU) monitor MAP signal circuit voltage and determine vacuum within intake manifold. Certain vehicle models will also use MAP sensor to determine barometric pressure when ignition is on and engine is off. This BARO reading may also be updated when engine is operated at wide open throttle.

DTC will run when the following conditions are met

1. Engine is operating on alternative fuel.
2. Engine speed is more than 500 RPM.
3. DTCs P0121, P0122, P0123 are not set.
4. Throttle Position (TP) angle is less than 4 percent.

DTC will set when AF ECU detects MAP sensor signal voltage more than 4.8 volts for at least 4 continuous seconds. When DTC is set, AF ECU will switch to gasoline fuel operation. AF ECU will not attempt alternative fuel operation until next key cycle.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Start engine and allow to idle. Using scan tool, communicate with PCM. Observe MAP sensor voltage. If voltage is more than 4.8 volts, go to step 5. If voltage is less than 4.8 volts, go to next step.
3. Using scan tool, communicate with AF ECU. Observe MAP sensor voltage. If voltage is more than 4.8 volts, go to step 11. If voltage is less than 4.8 volts, go to next step.
4. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
5. Monitor MAP sensor voltage on scan tool. Disconnect MAP sensor connector. (Scheme 6) If voltage is less than 0.25 volt, go to next step. If voltage is more than 0.25 volt, go to step 10.
6. Connect test light between ground and MAP sensor connector terminal "A" (Black/White wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 9.
7. Using DVOM, measure voltage between ground and MAP sensor connector terminal "C" (Gray wire). If voltage is less than 5.2 volts, go to step 14. If voltage is more than 5.2 volts, go to next step.
8. Check for short to voltage in all 5-volt reference circuits from PCM. See WIRING DIAGRAMS article. Some 5-volt reference circuits are shared within PCM. Disconnect AF ECU connector containing 5-volt reference circuit to determine if AF ECU is cause of short. Repair as necessary. After repairs, go to step 17. If components and circuits are okay, go to step 15.
9. Check for open or high resistance in Black/White wire between MAP sensor connector terminal "A" and PCM connector C2 terminal No. 14. (Scheme 5) Check for poor connections at MAP sensor and PCM. Repair circuit or connector as necessary. After repairs, go to step 17. If circuit and connections are okay, go to step 15.
10. Disconnect AF ECU connectors. AF ECU is located behind left front fascia, below headlight. (Scheme 2) Check for short to voltage in Light Green wire between MAP sensor connector terminal "B", PCM connector C2 terminal No. 62 and VF ECU Blue connector C001 terminal No. 14. (Scheme 3)and (Scheme 5). Repair as necessary. After repairs, go to step 17. If circuit is okay, go to step 15.
11. Turn ignition off. Disconnect AF ECU and MAP sensor connectors. (Scheme 2)and (Scheme 6). Check for continuity in Light Green wire between MAP sensor connector terminal "B" and VF ECU Blue connector C001 terminal No. 14. (Scheme 3) If continuity is indicated, go to step 13. If continuity is not indicated, go to next step.
12. Repair open in Light Green wire between MAP sensor and AF ECU. After repairs, go to step 17.
13. Check for poor connections at AF ECU. Repair as necessary. After repairs, go to step 17. If connections are okay, go to step 16.
14. Replace MAP sensor. After repairs, go to step 17.
15. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) PCM with correct vehicle software and calibration. See «POWERTRAIN CONTROL MODULE REPROGRAMMING»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-control-module-reprogramming) under PROGRAMMING. To perform CKP variation learn procedure, a switch-over to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switch-over. Perform CKP system variation learn procedure. See «CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__crankshaft-position-sensor-system-variation-learn) under PROGRAMMING. After performing repairs and procedures, go to step 17.
16. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to next step.
17. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

DTC P0112: IAT SENSOR CIRCUIT - LOW VOLTAGE (2.2L - GASOLINE)

Note. For circuit reference, see WIRING DIAGRAMS article.

Intake Air Temperature (IAT) sensor is a variable resistor, sometimes called a thermistor. IAT sensor measures temperature of air entering engine. PCM supplies 5 volts to IAT signal circuit. When IAT sensor is cold, sensor resistance is high. When air temperature increases, sensor resistance lowers. With high sensor resistance, PCM detects a high voltage on IAT signal circuit. With lower sensor resistance, PCM detects a lower voltage on IAT signal circuit. If PCM detects an excessively low IAT signal voltage, indicating a high temperature, this DTC will set.

1. DTCs P0117, P0118, P0125, P0502, or P0503 are not set.
2. Engine run time is more than 320 seconds.
3. Vehicle speed sensor indicates vehicle speed is more than 15 MPH.

IAT sensor signal voltage indicates intake air temperature is more than 262°F (128°C) for 3.13 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Using scan tool, observe IAT sensor temperature. If IAT sensor temperature is more than 262°F (128°C), go to step 4. If IAT sensor temperature is not more than 262°F (128°C), go to next step.
3. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or as close to FREEZE FRAME/FAILURE RECORDS data that you observed. If DTC fails this ignition cycle, go to next step. If DTC does not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Disconnect IAT sensor. (Scheme 6) Turn ignition on, engine off. Using scan tool, observe IAT sensor temperature. If IAT sensor temperature is less than -38°F (-39°C), go to step 6. If IAT sensor temperature is not less than -38°F (-39°C), go to next step.
5. Check Tan wire between IAT sensor and PCM for short to ground or short to Gray wire. If problem was found, repair as necessary. After repairs, go to step 9. If problem was not found, go to step 7.
6. Replace IAT sensor. After repair, go to step 9.
7. Turn ignition off. Disconnect PCM. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 9. If problem was not found, go to next step.
8. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
9. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
10. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

When vehicle is at ambient temperature, IAT sensor and ECT sensor temperatures should be relatively close to each other.

Intake Air Temperature (IAT) sensor is a thermistor. IAT sensor has high resistance when cold and low resistance when hot. Powertrain Control Module (PCM) supplies 5 volts and ground IAT sensor. When IAT resistance is high (cold sensor) signal voltage remains near 5 volts. As IAT sensor warms and resistance drops, signal voltage is low. PCM and the Alternate Fuel Engine Control Module (AF ECU) monitor IAT signal circuit voltage to determine temperature of air entering engine.

For DTC to run, the following conditions must be met

1. Engine is operating on alternative fuel.
2. Engine has been operating for more than 1.5 minutes.
3. Vehicle speed is more than one MPH.

DTC will set when AF ECU detects IAT sensor signal voltage less than 0.019 volt for at least 5 continuous seconds.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Using scan tool, communicate with AF ECU. Observe IAT sensor voltage. If IAT sensor voltage is less than 0.025 volt, go to next step. If IAT sensor voltage is more than 0.025 volt, go to step 4.
3. Using scan tool, communicate with PCM. Observe IAT sensor temperature. If IAT sensor temperature is more than 298°F (148°C), go to step 5. If IAT sensor temperature is less than 298°F (148°C), go to step 8.
4. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
5. Monitor IAT sensor temperature on scan tool. Disconnect IAT sensor. (Scheme 6) If IAT sensor temperature is more than 298°F (148°C), go to next step. If IAT sensor temperature is less than 298°F (148°C), go to step 9.
6. Turn ignition off. Disconnect PCM connectors. Disconnect AF ECU connectors. (Scheme 2) Check for short to ground or short to sensor ground circuit in Tan wire between IAT sensor connector terminal "B", PCM connector C2 terminal No. 20 and AF ECU Blue connector C001 terminal No. 13. (Scheme 3)and (Scheme 5). Repair as necessary. After repairs, go to step 12. If circuit is okay, go to next step.
7. Reconnect PCM connectors. Turn ignition on. Using scan tool, monitor IAT sensor temperature in PCM data list. If IAT sensor temperature is more than 298°F (148°C), go to step 10. If IAT sensor temperature is less than 298°F (148°C), go to step 11.
8. Check for open, high resistance or poor connections in Tan wire between IAT sensor connector terminal "B"and PCM connector C2 terminal No. 20. (Scheme 5) Repair circuit or connections as necessary. After repairs, go to step 12. If circuit and connections are okay, go to step 11.
9. Replace IAT sensor. After repairs, go to step 12.
10. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) PCM with correct vehicle software and calibration. See «POWERTRAIN CONTROL MODULE REPROGRAMMING»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-control-module-reprogramming) under PROGRAMMING. To perform CKP variation learn procedure, a switch-over to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switch-over. Perform CKP system variation learn procedure. See «CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__crankshaft-position-sensor-system-variation-learn) under PROGRAMMING. After performing repairs and procedures, go to step 12.
11. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to next step.
12. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

DTC P0112: IAT SENSOR CIRCUIT - LOW VOLTAGE (2.4L)

Note. For circuit reference, see WIRING DIAGRAMS article.

Intake Air Temperature (IAT) sensor uses a thermistor in order to control signal voltage to PCM. PCM supplies 5-volt reference and ground to sensor. When air is cold, resistance is high, and IAT signal voltage will be high. If intake air is warm, resistance is low, and IAT signal voltage will be low.

1. DTCs P0117, P0118, P0125, P0502, or P0503 are not set.
2. Engine run time is more than 320 seconds.
3. Vehicle Speed Sensor (VSS) indicates that vehicle speed is more than 15 MPH.

DTC sets when IAT sensor signal voltage indicates IAT is more than 262°F (128°C) for 3.125 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Using scan tool, observe IAT sensor temperature. If IAT sensor temperature is more than 262°F (128°C), go to step 4. If IAT sensor temperature is not more than 262°F (128°C), go to next step.
3. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or as close to FREEZE FRAME/FAILURE RECORDS data that you observed. If DTC fails this ignition cycle, go to next step. If DTC does not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Disconnect IAT sensor connector. (Scheme 7) Turn ignition on, engine off. If IAT is less than -22°F (-30°C), go to next step. If IAT is not less than -22°F (-30°C), go to step 6.
5. Turn ignition off. Replace IAT sensor. After repairs, go to step 11.
6. Turn ignition off. Using test light connected to battery voltage, probe IAT sensor connector terminal "B" (Tan wire) at IAT sensor connector. If test light is on, go to next step. If test light is off, go to step 9.
7. Turn ignition off. Disconnect PCM connector. Using test light connected to battery voltage, probe IAT sensor connector terminal "B" (Tan wire) at IAT sensor connector. If test light is on, go to next step. If test light is off, go to step 9.
8. Repair short to ground in Tan wire between IAT sensor and PCM. After repairs, go to step 11.
9. Check PCM connectors for a poor connection at the PCM. If problem was found, repair as necessary. After repairs, go to step 11. If problem was not found, go to next step.
10. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
11. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
12. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

If vehicle is at ambient temperature, compare IAT sensor to engine coolant temperature (ECT) sensor. IAT sensor and ECT sensor temperature readings should be relatively close to each other.

See TEMPERATURE VS RESISTANCE table to evaluate possibility of a skewed sensor.

TEMPERATURE VS RESISTANCE

DTC P0113: IAT SENSOR CIRCUIT - HIGH VOLTAGE (2.2L - GASOLINE)

Note. For circuit reference, see WIRING DIAGRAMS article.

Intake Air Temperature (IAT) sensor is a variable resistor, sometimes called a thermistor. IAT sensor measures temperature of air entering engine. PCM supplies 5 volts to IAT signal circuit. When IAT sensor is cold, sensor resistance is high. When air temperature increases, sensor resistance lowers. With high sensor resistance, PCM detects a high voltage on IAT signal circuit. With lower sensor resistance, PCM detects a lower voltage on IAT signal circuit. If PCM detects an excessively high IAT signal voltage, indicating a low temperature, this diagnostic trouble code (DTC) will set.

1. DTCs P0117, P0118, P0125, P0502, or P0503 are not set.
2. Engine run time is more than 320 seconds.
3. Vehicle Speed Sensor (VSS) indicates that vehicle speed is less than 15 MPH (24 km/h).

DTC sets when IAT sensor signal voltage indicates intake air temperature is less than -38°F (-39°C) for 3 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Using scan tool, observe IAT sensor temperature. If IAT sensor temperature is less than -36°F (-38°C), go to step 4. If IAT sensor temperature is not less than -36°F (-38°C), go to next step.
3. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or as close to FREEZE FRAME/FAILURE RECORDS data that you observed. If DTC fails this ignition cycle, go to next step. If DTC does not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Disconnect IAT sensor. (Scheme 6) Connect fused jumper wire (3-amp) between IAT sensor connector terminals. Turn ignition on, engine off. Using scan tool, observe IAT sensor temperature. If IAT sensor temperature is more than 262°F (128°C), go to step 8. If IAT sensor temperature is not more than 262°F (128°C), go to next step.
5. Turn ignition off. Connect fused jumper wire (3-amp) between IAT sensor connector terminal "B" (Tan wire) and ground. Turn ignition on, engine off. Using scan tool, observe IAT sensor temperature. If IAT sensor temperature is more than 262°F (128°C), go to step 7. If IAT sensor temperature is not more than 262°F (128°C), go to next step.
6. Check Tan wire between IAT sensor and PCM for open or high resistance. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 9.
7. Check Gray wire between IAT sensor and PCM for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 9.
8. Check IAT sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 10.
9. Check PCM connectors for poor connections. If problem is found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 11.
10. Replace IAT sensor. After repairs, go to step 12.
11. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
12. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
13. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

When vehicle is at ambient temperature, IAT sensor and ECT sensor temperatures should be relatively close to each other.

If a short to a separate 5-volt source occurs, this DTC may set. If this condition exists, a continuity test to all other PCM 5-volt reference circuits will be necessary.

Intake Air Temperature (IAT) sensor is a thermistor. IAT sensor has high resistance when cold and low resistance when hot. Powertrain Control Module (PCM) supplies 5 volts and ground IAT sensor. When IAT resistance is high (cold sensor) signal voltage remains near 5 volts. As IAT sensor warms and resistance drops, signal voltage is low. PCM and the Alternate Fuel Engine Control Module (AF ECU) monitor IAT signal circuit voltage to determine temperature of air entering engine.

For DTC to run, the following conditions must be met

1. Engine is operating on alternative fuel.
2. Engine has been operating for more than 1.5 minutes when engine start-up temperature is more than 32°F (0°C).
3. Engine has been operating for more than 10 minutes when engine start-up temperature is 32°F (0°C) or less.
4. Vehicle speed is less than one MPH for at least 10 seconds.
5. Calculated air flow is less than 250 grams per second for at least 10 seconds.

DTC will set when AF ECU detects IAT sensor signal voltage is more than 4.8 volts for at least 5 continuous seconds.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Using scan tool, communicate with PCM. Observe IAT sensor temperature. If IAT sensor temperature is less than -27°F (-34°C), go to step 5. If IAT sensor temperature is more than -27°F (-34°C), go to next step.
3. Using scan tool, communicate with AF ECU. Observe IAT sensor voltage. If IAT sensor voltage is more than 4.8 volts, go to step 12. If IAT sensor voltage is less than 4.8 volts, go to next step.
4. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
5. Monitor IAT sensor temperature on scan tool. Disconnect IAT sensor. (Scheme 6) Connect a fused jumper between IAT sensor connector terminals "A" (Gray wire) and "B" (Tan wire). If IAT sensor temperature is more than 298°F (148°C), go to step 8. If IAT sensor temperature is less than 298°F (148°C), go to next step. If fused jumper blows, repair short to voltage in Tan wire. After repairing short to voltage, check for an open IAT sensor and replace if necessary.
6. Connect fused jumper between IAT sensor connector terminal "B" (Tan wire) and ground. If IAT sensor temperature is more than 298°F (148°C), go to step 9. If IAT sensor temperature is less than 298°F (148°C), go to next step.
7. Turn ignition off. Disconnect PCM connectors. Using DVOM, check for continuity is Tan wire between IAT sensor and PCM connector C2 terminal No. 20. (Scheme 5) If continuity is indicated, go to step 11. If continuity is not indicated, go to step 10.
8. Replace IAT sensor. After repairs, go to step 17.
9. Repair open in Gray wire between the IAT sensor and PCM connector C2 terminal No. 28. (Scheme 5) After repairs, go to step 17.
10. Repair open in Tan wire between IAT sensor and PCM. After repairs, go to step 17.
11. Check for poor connections at PCM. Repair as necessary. After repairs, go to step 17. If connections are okay, go to step 15.
12. Turn ignition off. Disconnect AF ECU Blue connector. (Scheme 2) Using DVOM, check for continuity is Tan wire between IAT sensor and AF ECU Blue connector C001 terminal No. 20. (Scheme 3) If continuity is indicated, go to next step. If continuity is not indicated, go to step 14.
13. Check for poor connections at AF ECU. Repair as necessary. After repairs, go to step 17. If connections are okay, go to step 16.
14. Repair open in Tan wire between IAT sensor and AF ECU. After repairs, go to step 17.
15. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) PCM with correct vehicle software and calibration. See «POWERTRAIN CONTROL MODULE REPROGRAMMING»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-control-module-reprogramming) under PROGRAMMING. To perform CKP variation learn procedure, a switch-over to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switch-over. Perform CKP system variation learn procedure. See «CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__crankshaft-position-sensor-system-variation-learn) under PROGRAMMING. After performing repairs and procedures, go to step 17.
16. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to next step.
17. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Intake Air Temperature (IAT) sensor uses a thermistor to control signal voltage to PCM. PCM supplies a 5-volt reference and ground to sensor. When air is cold, resistance is high, and IAT signal voltage will be high. If intake air is warm, resistance is low, and IAT signal voltage will be low.

1. DTCs P0117, P0118, P0125, P0502, or P0503 are not set.
2. Engine run time is more than 320 seconds.
3. Engine Coolant Temperature (ECT) is more than -40°F (-40°C).
4. Vehicle speed sensor indicates vehicle speed is less than 15 MPH.

IAT sensor signal voltage indicates IAT is less than -40°F (-40°C) for 3.13 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on, engine off. Using scan tool, observe IAT parameter. If scan tool indicates IAT parameter is less than -34°F (-37°C), go to step 4. If scan tool does not indicate IAT parameter is less than -34°F (-37°C), go to next step.
3. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or as close to FREEZE FRAME/FAILURE RECORDS data that you observed. If DTC fails this ignition cycle, go to next step. If DTC does not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Disconnect IAT sensor. (Scheme 7) Connect fused jumper wire (3-amp) between IAT sensor connector terminals. Using scan tool, observe IAT parameter. If scan tool indicates IAT parameter is more than 275°F (135°C), go to step 6. If scan tool does not indicate IAT parameter is more than 275°F (135°C), go to next step.
5. Connect fused jumper wire (3-amp) between IAT sensor connector terminal "B" (Tan wire) and ground. Using scan tool, observe IAT parameter. If scan tool indicates IAT parameter is more than 275°F (135°C), go to step 7. If scan tool does not indicate IAT parameter is more than 275°F (135°C), go to step 8.
6. Check Tan wire between IAT sensor and PCM for short to voltage. If problem was found, repair as necessary. After repairs, go to step 13. If problem was not found, go to step 10.
7. Check Gray wire on "J" body and Black wire on "N" body between IAT sensor and PCM for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 13. If problem was not found, go to step 9.
8. Check Tan wire between IAT sensor and PCM for open. If problem was found, repair as necessary. After repairs, go to step 13. If problem was not found, go to next step.
9. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 13. If problem was not found, go to step 12.
10. Check IAT sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 13. If problem was not found, go to next step.
11. Replace IAT sensor. After repairs, go to step 13.
12. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
13. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
14. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

If vehicle is at ambient temperature, compare IAT sensor reading to ECT sensor reading. Readings should be relatively close to each other.

Use TEMPERATURE VS RESISTANCE table in DTC P0112: IAT SENSOR CIRCUIT - LOW VOLTAGE (2.4L) to evaluate possibility of a skewed sensor.

If a short to a separate 5-volt source occurs, this DTC may set. If this is found to be problem, a continuity test to all other PCM circuits will be necessary to diagnose specific circuit.

DTC P0117: ECT SENSOR CIRCUIT - LOW VOLTAGE (GASOLINE)

Note. For circuit reference, see WIRING DIAGRAMS article.

Engine Coolant Temperature (ECT) sensor is a variable resistor, sometimes called a thermistor, that measures temperature of engine coolant. PCM supplies 5 volts to ECT signal circuit. When ECT is cold, sensor resistance is high. When ECT increases, sensor resistance lowers. With high sensor resistance, PCM detects a high voltage on ECT signal circuit. With lower sensor resistance, PCM detects a lower voltage on ECT signal circuit. If PCM detects an excessively low ECT signal voltage, which is a high temperature indication, DTC will set.

1. Engine has been running more than 128 seconds.

DTC sets when ECT sensor indicates an engine coolant temperature more than 280°F (138°C) for more than 6.25 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, observe ECT sensor temperature. If ECT sensor temperature is more than 280°F (138°C), go to step 4. If ECT sensor temperature is not more than 280°F (138°C), go to next step.
3. Observe FREEZE FRAME AND/OR FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or as close to FREEZE FRAME/FAILURE RECORDS data that you observed. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Disconnect ECT sensor connector. (Scheme 6)or (Scheme 7). Turn ignition on, engine off. Using scan tool, observe ECT sensor temperature. If scan tool indicates ECT sensor temperature is less than -36°F (-38°C), go to step 6. If scan tool does not indicate ECT sensor temperature value is less than -36°F (-38°C), go to next step.
5. Turn ignition off. Disconnect PCM. Check Yellow wire between ECT sensor and PCM for short to ground or short to any reference low circuit. If problem was found, repair as necessary. After repairs, go to step 8. If problem was not found, go to step 7.
6. Replace ECT sensor. After repairs, go to step 8.
7. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
8. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
9. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

An overheating condition may cause DTC to set.

After starting engine, ECT sensor temperature should rise steadily to about 194°F (90°C), then stabilize after thermostat opens.

See TEMPERATURE VS RESISTANCE table in DTC P0112: IAT SENSOR CIRCUIT - LOW VOLTAGE (2.4L) in order to test ECT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor could result in poor driveability concerns.

Engine Coolant Temperature (ECT) sensor is a thermistor. ECT sensor has high resistance when cold and low resistance when hot. Powertrain Control Module (PCM) supplies 5 volts and ground to ECT sensor. ECT resistance is high (cold sensor) ECT signal voltage remains near 5 volts. As ECT sensor warms and resistance drops, signal circuit voltage is low. PCM and Alternate Fuel Engine Control Unit (AF ECU) monitor ECT signal circuit voltage to determine engine temperature.

For DTC to run, the engine must be operating on alternative fuel and running for more than 5 seconds. DTC will set when AF ECU detects ECT sensor signal voltage of less than 0.019 volt for at least 5 continuous seconds.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Using scan tool, communicate with AF ECU. Observe ECT sensor voltage. If ECT sensor voltage is less than 0.025 volts, go to next step. If ECT sensor voltage is more than 0.025 volts, go to step 4.
3. Using scan tool, communicate with PCM. Observe ECT sensor temperature. If ECT sensor temperature is more than 298°F (148°C), go to step 5. If ECT sensor temperature is less than 298°F (148°C), go to step 8.
4. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
5. Monitor ECT sensor temperature on scan tool. Disconnect IAT sensor. (Scheme 6) If ECT sensor temperature is more than 298°F (148°C), go to next step. If ECT sensor temperature is less than 298°F (148°C), go to step 9.
6. Turn ignition off. Disconnect PCM connectors. PCM is located inside right front fender. Disconnect the AF ECU Blue connector. AF ECU is located behind left front fascia, below headlight. Check for short to ground or short to sensor ground in Yellow wire between ECT connector terminal "B", PCM connector C1 terminal No. 54 and AF ECU connector C001 terminal No. 12. (Scheme 3)and (Scheme 5). Repair as necessary. After repairs, go to step 12. If circuit is okay, go to next step.
7. Reconnect PCM connectors. Turn ignition on. Monitor ECT sensor temperature in PCM data list. If ECT sensor temperature is more than 298°F (148°C), go to step 10. If ECT sensor temperature is more than 298°F (148°C), go to step 11.
8. Check for open, high resistance or poor connections in Yellow wire between ECT connector terminal "B" and PCM connector C1 terminal No. 54. (Scheme 5) Repair circuit or connectors as necessary. After repairs, go to step 12. If circuit and connections are okay, go to step 11.
9. Replace ECT sensor. After repairs, go to step 12.
10. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) PCM with correct vehicle software and calibration. See «POWERTRAIN CONTROL MODULE REPROGRAMMING»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-control-module-reprogramming) under PROGRAMMING. To perform CKP variation learn procedure, a switch-over to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switch-over. Perform CKP system variation learn procedure. See «CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__crankshaft-position-sensor-system-variation-learn) under PROGRAMMING. After performing repairs and procedures, go to step 12.
11. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to next step.
12. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

DTC P0118: ECT SENSOR CIRCUIT - HIGH VOLTAGE (GASOLINE)

Note. For circuit reference, see WIRING DIAGRAMS article.

Engine Coolant Temperature (ECT) sensor is a variable resistor, sometimes called a thermistor, that measures temperature of engine coolant. PCM supplies 5 volts to ECT signal circuit. When ECT is cold, sensor resistance is high. When ECT increases, sensor resistance lowers. With high sensor resistance, PCM detects a high voltage on ECT signal circuit. With lower sensor resistance, PCM detects a lower voltage on ECT signal circuit. If PCM detects an excessively high ECT signal voltage, which is a low temperature indication, DTC will set.

1. Engine has been running more than 60 seconds.

ECT sensor temperature is less than -40°F (-40°C) for more than 6.25 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, observe ECT sensor temperature. If ECT sensor temperature is less than -36°F (-38°C), go to step 4. If ECT sensor temperature is not less than -36°F (-38°C), go to next step.
3. Observe FREEZE FRAME AND/OR FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or as close to FREEZE FRAME/FAILURE RECORDS data that you observed. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Disconnect ECT sensor. (Scheme 6)or (Scheme 7). Connect fused jumper wire (3-amp) between ECT sensor connector terminals. Turn ignition on, engine off. Using scan tool, observe ECT sensor temperature. If scan tool indicates ECT sensor temperature is more than 280°F (138°C), go to step 8. If scan tool does not indicate ECT sensor temperature is more than 280°F (138°C), go to next step.
5. Turn ignition off. Connect fused jumper wire (3-amp) between ECT sensor connector terminal "B" (Yellow wire) and ground. Turn ignition on, engine off. Using scan tool, observe ECT sensor temperature. If scan tool indicates ECT sensor temperature more than 280°F (138°C), go to step 7. If scan tool does not indicate ECT sensor temperature more than 280°F (138°C), go to next step.
6. Check Yellow wire between ECT sensor and PCM for short to voltage, high resistance and open circuit. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to next step.
7. Check Brown wire on "J" body and Black/White wire on "N" body between ECT sensor and PCM for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 9.
8. Check ECT sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 10.
9. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 11.
10. Replace ECT sensor. After repairs, go to step 12.
11. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
12. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
13. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

If a short to a separate 5-volt source occurs, this DTC may set. If this is the problem, a continuity test to all other PCM circuits will be necessary to diagnose specific circuit.

After starting engine, ECT should rise steadily to about 194°F (90°C) then stabilize after thermostat opens.

See TEMPERATURE VS RESISTANCE table in DTC P0112: IAT SENSOR CIRCUIT - LOW VOLTAGE (2.4L) to test ECT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor could result in poor driveability concerns.

Engine Coolant Temperature (ECT) sensor is a thermistor. ECT sensor has high resistance when cold and low resistance when hot. Powertrain Control Module (PCM) supplies 5 volts and ground to ECT sensor. ECT resistance is high (cold sensor) ECT signal voltage remains near 5 volts. As ECT sensor warms and resistance drops, signal circuit voltage is low. PCM and Alternate Fuel Engine Control Unit (AF ECU) monitor ECT signal circuit voltage to determine engine temperature.

For DTC to run, engine must be operating on alternative fuel with engine running for more than 5 seconds when Intake Air Temperature (IAT) is more than 32°F (0°C) or engine running for more than 10 minutes when IAT is less than 32°F (0°C). DTC will set when AF ECU detects ECT sensor signal voltage of more than 4.8 volts for at least 5 continuous seconds.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Using scan tool, communicate with PCM. Observe ECT sensor temperature. If ECT sensor temperature is less than -27°F (-34°C), go to step 5. If ECT sensor temperature is more than -27°F (-34°C), go to next step.
3. Using scan tool, communicate with AF ECU. Observe ECT sensor voltage. If ECT sensor voltage is more than 4.8 volts, go to step 12. If ECT sensor voltage is less than 4.8 volts, go to next step.
4. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
5. Monitor ECT sensor temperature on scan tool. Disconnect ECT sensor. (Scheme 6) Connect a fused jumper between ECT sensor connector terminals. If ECT sensor temperature is more than 298°F (148°C), go to step 8. If ECT sensor temperature is less than 298°F (148°C), go to next step. If fused jumper blows, repair short to voltage in Yellow wire. After repairing short to voltage, check for an open ECT sensor and replace if necessary.
6. Monitor ECT sensor temperature on scan tool. Connect a fused jumper between ECT sensor connector terminal "B" (Yellow wire) and ground. If ECT sensor temperature is more than 298°F (148°C), go to step 9. If ECT sensor temperature is less than 298°F (148°C), go to next step.
7. Turn ignition off. Disconnect PCM connectors. PCM is located inside right front fender. Using DVOM, check for continuity in Yellow wire between ECT sensor connector terminal "B" and PCM connector C1 terminal No. 54. (Scheme 5) If continuity is indicated, go to step 11. If continuity is not indicated, go to step 10.
8. Replace ECT sensor. After repairs, go to step 17.
9. Repair open in Brown wire between ECT sensor connector terminal "A" and PCM connector C2 terminal No. 27. (Scheme 5) After repairs, go to step 17.
10. Repair open in Yellow wire between ECT and PCM. After repairs, go to step 17.
11. Check for poor connections at PCM. Repair as necessary. After repairs, go to step 17. If connections are okay, go to step 15.
12. Turn ignition off. Disconnect AF ECU Blue connector. Disconnect ECT sensor. Using DVOM, check for continuity in Yellow wire between ECT sensor connector terminal "B" and AF ECU connector C001 terminal No. 12. (Scheme 3) If continuity is indicated, go to step 14. If continuity is not indicated, go to next step.
13. Repair open in Yellow wire between ECT and AF ECU. After repairs, go to step 17.
14. Check for poor connections at AF ECU. Repair as necessary. After repairs, go to step 17. If connections are okay, go to step 16.
15. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) PCM with correct vehicle software and calibration. See «POWERTRAIN CONTROL MODULE REPROGRAMMING»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-control-module-reprogramming) under PROGRAMMING. To perform CKP variation learn procedure, a switch-over to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switch-over. Perform CKP system variation learn procedure. See «CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__crankshaft-position-sensor-system-variation-learn) under PROGRAMMING. After performing repairs and procedures, go to step 17.
16. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to next step.
17. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Throttle Position (TP) sensor is a potentiometer. Powertrain Control Module (PCM) supplies 5 volts and ground to TP sensor. When throttle is depressed, TP signal voltage rises to near 5 volts. As throttle is released, TP signal voltage drops to around 0.6 volt. PCM and Alternate Fuel Engine Control Unit (AF ECU) monitor TP signal circuit voltage and determine angle (or opening) of throttle blade.

For DTC to run, the following conditions must be met

1. Engine is operating on alternative fuel.
2. Engine has been operating for more than 2 seconds.
3. No AF ECU DTCs are set.
4. DTCs P1215, P1432 and P1433 can be set.
5. Engine MAP is less than 45 kPa.
6. TP sensor angle has changed less than 2 percent for 2 continuous seconds.

DTC will set when TP sensor angle (percent) is more than specified at given engine speed. For specifications, see THROTTLE POSITION SENSOR ANGLE SPECIFICATIONS table.

THROTTLE POSITION SENSOR ANGLE SPECIFICATIONS

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. If DTCs P0106, P0107 or P0108 are set, diagnose those DTCs first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions). If DTCs P0106, P0107 or P0108 are not set, go to next step.
3. Turn ignition on. Using scan tool, communicate with AF ECU. Observe TP sensor angle. If throttle angle is less than 2 percent, go to step 4. If throttle angle is more than 2 percent, go to step 7.
4. Monitor TP sensor angle. Depress throttle slowly to Wide Open Throttle (WOT) position. If throttle angle increases to more than 98, go to next step. If throttle angle does not increase to more than 98, go to step 7.
5. Release throttle. If throttle angle drops to less than 2 percent, go to next step. If throttle angle does not drop to less than 2 percent, go to step 7.
6. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l). NOTE: During next step, additional DTCs may set.
7. Monitor TP sensor voltage on scan tool. Disconnect TP sensor connector. Connect fused jumper wire between TP sensor connector terminals "A" (Gray wire) and "C" (Dark Blue wire). If TP sensor voltage is more than 4.9 volts, go to next step. If TP sensor voltage is less than 4.9 volts, go to step 11.
8. Remove fused jumper. Using DVOM, measure voltage between ground and TP sensor connector terminal "A" (Gray wire). If voltage is 4.8-5.2 volts, go to next step. If voltage is not 4.8-5.2 volts, go to step 13.
9. Monitor TP sensor voltage on scan tool. Connect a fused jumper wire between TP sensor connector terminal "C" (Dark Blue wire) and ground. If TP voltage is less than 0.08 volt, go to next step. If TP voltage is more than 0.08 volt, go to step 15. If fused jumper blows, repair short to voltage in Dark Blue wire. NOTE: During next step, additional DTCs may set.
10. Monitor TP sensor voltage on scan tool. Connect a fused jumper wire between TP sensor connector terminals "A" (Gray wire) and "C" (Dark Blue wire). Connect a second fused jumper wire between TP sensor connector terminals "A" (Gray wire) and "B" (Black wire). If TP voltage is less than 0.08 volt, go to step 12. If TP voltage is more than 0.08 volt, go to step 16.
11. Check for short to ground or short to sensor ground circuit in Dark Blue wire between TP sensor, PCM connector C1 terminal No. 21 and AF ECU Blue connector C001 terminal No. 27. (Scheme 3)and (Scheme 5). Repair as necessary. After repairs, go to step 20. If circuit is okay, go to step 19.
12. If fused jumper blows, check for short to voltage in Dark Blue wire between TP sensor, PCM connector C1 terminal No. 21 and AF ECU Blue connector C001 terminal No. 27. (Scheme 3)and (Scheme 5). If fused jumper does not blow, repair short to 5-volt reference circuit (Gray wire) in Dark Blue wire. Repair as necessary. After repairs, go to step 20. If circuit is okay, go to step 17.
13. Turn ignition off. Disconnect both AF ECU connectors. AF ECU is located behind left front fascia, below headlight. Turn ignition on. Using DVOM, measure voltage between ground and TP sensor connector terminal "A" (Gray wire). If voltage is 4.8-5.2 volts, go to step 19. If voltage is not 4.8-5.2 volts, go to next step.
14. If voltage is more than 5.2 volts, check for short to voltage in Gray wire. If voltage is less than 4.8 volts, check for short to ground or high resistance in Gray wire. Repair as necessary. After repairs, go to step 20. If circuit is okay, go to step 18.
15. Check for open or high resistance in Dark Blue wire between TP sensor connector terminal "C" and AF ECU Blue connector C001 terminal No. 27. (Scheme 3) Also check for poor connections at AF ECU and any in-line connectors. Repair as necessary. After repairs, go to step 20. If circuit and connections are okay, go to step 19.
16. Check for short to ground or high resistance in Black wire between TP sensor connector terminal "B" and PCM connector C2 terminal No. 57. (Scheme 5) Also check for poor connections at PCM and any in-line connectors. Repair as necessary. After repairs, go to step 20. If circuit and connections are okay, go to step 18.
17. Replace TP sensor. After repairs, go to step 20.
18. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) PCM with correct vehicle software and calibration. See «POWERTRAIN CONTROL MODULE REPROGRAMMING»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-control-module-reprogramming) under PROGRAMMING. To perform CKP variation learn procedure, a switch-over to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switch-over. Perform CKP system variation learn procedure. See «CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__crankshaft-position-sensor-system-variation-learn) under PROGRAMMING. After performing repairs and procedures, go to step 20.
19. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to next step.
20. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

DTC P0122: TP SENSOR CIRCUIT - LOW VOLTAGE (GASOLINE)

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM provides TP sensor with a 5-volt reference circuit and a low reference circuit. Rotation of TP sensor rotor from closed throttle position to wide open throttle (WOT) position provides PCM with a signal voltage from less than one volt to more than 4 volts through TP sensor signal circuit. If PCM detects an excessively low signal voltage, this DTC will set.

1. Engine is running.

DTC sets when TP sensor signal voltage is less than 0.1 volt for more than 2 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Using scan tool, observe TP SENSOR VOLTAGE parameter. If scan tool indicates TP sensor voltage is less than 0.1 volt, go to step 4. If scan tool does not indicate TP sensor voltage is less than 0.1 volt, go to next step.
3. Observe FREEZE FRAME AND/OR FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or as close to FREEZE FRAME/FAILURE RECORDS data that you observed. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Disconnect TP sensor harness connector. (Scheme 6)or (Scheme 7). Connect fused jumper wire between TP sensor connector terminals "A" (Gray wire on "J" body or Gray/Black wire on "N" body) and "C" (Dark Blue wire). (Scheme 9) Turn ignition on, engine off. Using scan tool, observe TP SENSOR VOLTAGE PARAMETER. If scan tool indicates TP SENSOR VOLTAGE is 5 volts, go to step 11. If scan tool does not indicate TP SENSOR VOLTAGE is 5 volts, go to next step.
5. Disconnect fused jumper wire. Using DVOM, measure voltage between TP sensor connector terminals "A" (Gray wire on "J" body or Gray/Black wire on "N" body) and "B" (Black wire). If voltage is near 5 volts, go to step 9. If voltage is not near 5 volts, go to next step.
6. Check Gray wire on "J" body or Gray/Black wire on "N" body between TP sensor and PCM for open or high resistance. If problem was found, repair as necessary. After repairs, go to step 14. If problem was not found, go to next step.
7. Check all 5-volt reference circuits for short to ground. If problem was found, repair as necessary. After repairs, go to step 14. If problem was not found, go to next step.
8. Using DVOM connected between TP sensor connector terminals "A" (Gray wire on "J" body and Gray/Black wire on "N" body) and "B" (Black wire), observe voltage while disconnecting all sensors, one at a time, that use 5-volt reference signal. A change in voltage indicates faulty component. If problem was found, replace that component as necessary. After repairs, go to step 14. If problem was not found, go to step 10.
9. Using DVOM, check Dark Blue wire between TP sensor and PCM for open, high resistance, or short to ground. If problem was found, repair as necessary. After repairs, go to step 14. If problem was not found, go to next step.
10. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 14. If problem was not found, go to step 13.
11. Check TP sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 14. If problem was not found, go to next step.
12. Replace TP sensor. See THROTTLE POSITION SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 14.
13. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
14. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
15. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation.

If other DTCs are set for components that share the same ground and/or 5-volt reference circuit, check for faulty connections or wiring. PCM 5-volt reference circuits are internally connected within PCM. Also, using FREEZE FRAME data may aid in determining conditions when DTC was set.

Throttle Position (TP) sensor is a potentiometer. Powertrain Control Module (PCM) supplies 5 volts and ground to TP sensor. When throttle is depressed, TP signal voltage rises to near 5 volts. As throttle is released, TP signal voltage drops to around 0.6 volt. PCM and Alternate Fuel Engine Control Unit (AF ECU) monitor TP signal circuit voltage and determine angle (or opening) of throttle blade.

For DTC to run, engine must be operating on alternate fuel. DTC will set when AF ECU detects TP sensor signal voltage of less than 0.09 volt for at least one continuous second.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, communicate with PCM. Observe TP sensor voltage. If TP sensor voltage is less than 0.09 volt, go to step 6. If TP sensor voltage is more than 0.09 volt, go to next step.
3. Using scan tool, communicate with AF ECU. Observe TP sensor voltage. If TP sensor voltage is less than 0.09 volt, go to step 14. If TP sensor voltage is more than 0.09 volt, go to next step.
4. Open and close throttle plate while monitoring TP sensor voltage. If TP sensor voltage drops below 0.09 volt at any time, go to step 6. If TP sensor voltage does not drop below 0.09 volt at any time, go to next step.
5. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
6. Disconnect TP sensor. (Scheme 6) Monitor TP sensor voltage on scan tool. Connect fused jumper between TP sensor connector terminals "A" (Gray wire) and "C" (Dark Blue wire). If TP sensor voltage is more than 4.8 volts, go to step 12. If TP sensor voltage is less than 4.8 volts, go to next step.
7. Remove jumper wire. Ensure ignition is on. Using DVOM, measure voltage between TP sensor connector terminal "A" (Gray wire) and ground. If voltage is less than 4.8 volts, go to step 10. If voltage is more than 4.8 volts, go to next step.
8. Check for open or high resistance in Dark Blue wire between TP sensor and PCM connector C1 terminal No. 21. (Scheme 5) Repair as necessary. After repairs, go to step 15. If circuit is okay, go to next step.
9. Check for short to ground or short to sensor ground circuit Dark Blue wire. Disconnect AF ECU connectors to determine if AF ECU is internally shorted. AF ECU is located behind left front fascia, below headlight. Repair as necessary. After repairs, go to step 15. If circuit and AF ECU are okay, go to step 13.
10. Check for open or high resistance in Gray wire between TP sensor connector terminal "A" and PCM connector C2 terminal No. 33. (Scheme 5) Repair as necessary. After repairs, go to step 15. If circuit is okay, go to next step.
11. Check for short to ground in all 5-volt reference circuits from PCM. See WIRING DIAGRAMS article. Some 5-volt reference circuits are shared within PCM. Disconnect AF ECU connector containing 5-volt reference circuit to determine if AF ECU is cause of short. Disconnect all other sensors connected to PCM 5-volt reference circuits to determine if a sensor is cause of short. Repair or replace components or circuits as necessary. After repairs, go to step 15. If components and circuits are okay, go to step 13.
12. Replace TP sensor. After repairs, go to step 15.
13. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) PCM with correct vehicle software and calibration. See «POWERTRAIN CONTROL MODULE REPROGRAMMING»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-control-module-reprogramming) under PROGRAMMING. To perform CKP variation learn procedure, a switch-over to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switch-over. Perform CKP system variation learn procedure. See «CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__crankshaft-position-sensor-system-variation-learn) under PROGRAMMING. After performing repairs and procedures, go to step 15.
14. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to next step.
15. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

DTC P0123: TP SENSOR CIRCUIT - HIGH VOLTAGE (GASOLINE)

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM provides TP sensor with a 5-volt reference circuit and a low reference circuit. Rotation of TP sensor rotor from closed throttle position to Wide Open Throttle (WOT) position provides PCM with a signal voltage from less than one volt to more than 4 volts through TP sensor signal circuit. If PCM detects an excessively high signal voltage, DTC will set.

1. Engine is running.
2. DTCs P0107 or P0108 are not set.
3. Manifold Absolute Pressure (MAP) is less than 60 kPa.
4. Engine speed is less than 1500 RPM.

DTC sets when TP sensor signal voltage is more than 4.8 volts for more than 2 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on, engine off. Using scan tool, observe TP SENSOR VOLTAGE parameter with throttle closed. If scan tool indicates TP SENSOR VOLTAGE is more than 4.9 volts, go to step 4. If scan tool does not indicate TP SENSOR VOLTAGE is more than 4.9 volts, go to next step.
3. Observe FREEZE FRAME AND/OR FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or as close to FREEZE FRAME/FAILURE RECORDS data that you observed. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Disconnect TP sensor. (Scheme 6)or (Scheme 7). Turn ignition on, engine off. Using scan tool, observe TP SENSOR VOLTAGE parameter. If scan tool indicates TP voltage is zero volts, go to next step. If scan tool does not indicate TP voltage is zero volts, go to step 8.
5. Using DVOM, measure voltage between TP sensor connector terminal "A" (Gray wire on "J" body and Gray/Black wire on "N" body) and ground. (Scheme 9) If 5-volt reference circuit voltage is 5 volts, go to next step. If 5-volt reference circuit is not 5 volts, go to step 9.
6. Connect test light between TP sensor connector terminal "B" (Black wire) and battery voltage. If test light is on, go to step 10. If test light is off, go to next step.
7. Check Black wire between TP sensor and PCM for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 14. If problem was not found, go to step 10.
8. Check Dark Blue wire between TP sensor and PCM for short to voltage. If problem was found, repair as necessary. After repairs, go to step 14. If problem was not found, go to step 11.
9. Check all 5-volt reference circuits for short to voltage. If problem was found, repair as necessary. After repairs, go to step 14. If problem was not found, go to step 10.
10. Check TP sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 14. If problem was not found, go to step 12.
11. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 14. If problem was not found, go to step 13.
12. Replace TP sensor. See THROTTLE POSITION SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 14.
13. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
14. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
15. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation. If other DTCs are set for components that share the same ground and/or 5-volt reference circuit, check for faulty connections or wiring. PCM 5-volt reference circuits are internally connected within PCM. Also, using FREEZE FRAME data may aid in determining conditions when DTC was set.

Throttle Position (TP) sensor is a potentiometer. Powertrain Control Module (PCM) supplies 5 volts and ground to TP sensor. When throttle is depressed, TP signal voltage rises to near 5 volts. As throttle is released, TP signal voltage drops to around 0.6 volt. PCM and Alternate Fuel Engine Control Unit (AF ECU) monitor TP signal circuit voltage and determine angle (or opening) of throttle blade.

For DTC to run, engine must be operating on alternate fuel. DTC will set when AF ECU detects TP sensor signal voltage of more than 4.9 volts for at least one continuous second.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, communicate with PCM. Observe TP sensor voltage. Depress accelerator pedal to floor. If TP sensor voltage is more than 4.9 volts, go to step 6. If TP sensor voltage is less than 4.9 volts, go to next step.
3. Continue to depress accelerator pedal. Using scan tool, communicate with AF ECU. Observe TP sensor voltage. If TP sensor voltage is more than 4.9 volts, go to step 12. If TP sensor voltage is less than 4.9 volts, go to next step.
4. Open and close throttle plate while monitoring TP sensor voltage. If TP sensor voltage is more than 4.9 volts at any time, go to step 6. If TP sensor voltage is not more than 4.9 volts at any time, go to next step.
5. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
6. Disconnect TP sensor. (Scheme 6) Monitor TP sensor voltage on scan tool. If TP sensor voltage is less than.75 volt, go to next step. If TP sensor voltage is more than.75 volt, go to step 11.
7. Connect test light between battery voltage and TP sensor connector terminal "B" (Black wire). If test light is illuminated, go to next step. If test light is not illuminated, go to step 10.
8. Using DVOM, measure voltage between TP sensor connector terminal "A" (Gray wire) and ground. If voltage is less than 5.2 volts, go to step 15. If voltage is more than 5.2 volts, go to next step.
9. Check for short to voltage in all 5-volt reference circuits from PCM. See WIRING DIAGRAMS article. Some 5-volt reference circuits are shared within PCM. Disconnect AF ECU connector containing 5-volt reference circuit to determine if AF ECU is cause of short. Disconnect all other sensors connected to PCM 5-volt reference circuits to determine if a sensor is cause of short. Repair or replace components or circuits as necessary. After repairs, go to step 18. If components and circuits are okay, go to step 16.
10. Check for open or high resistance in Black wire between TP sensor connector terminal "B" and PCM connector C1 terminal No. 57. (Scheme 5) Check for poor connections at PCM and TP sensor. Repair as necessary. After repairs, go to step 18. If connections and circuit are okay, go to step 16.
11. Check for short to voltage in Dark Blue wire between TP sensor connector terminal "C" and AF ECU Blue connector C001 terminal No. 27. (Scheme 3) Disconnect AF ECU connectors to determine if AF ECU is internally shorted. AF ECU is located behind left front fascia, below headlight. Repair as necessary. After repairs, go to step 18. If circuit and AF ECU are okay, go to step 16.
12. Turn ignition off. Disconnect AF ECU connectors to determine if AF ECU is internally shorted. AF ECU is located behind left front fascia, below headlight. Using DVOM, check for continuity of Dark Blue wire between TP sensor connector terminal "C" and AF ECU Blue connector C001 terminal No. 27. (Scheme 3) If continuity is indicated, go to step 14. If continuity is not indicated, go to next step.
13. Repair open in Dark Blue wire. After repairs, go to step 18.
14. Check for poor connections at AF ECU. Repair as necessary. After repairs, go to step 18. If connections are okay, go to step 17.
15. Replace TP sensor. After repairs, go to step 18.
16. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) PCM with correct vehicle software and calibration. See «POWERTRAIN CONTROL MODULE REPROGRAMMING»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-control-module-reprogramming) under PROGRAMMING. To perform CKP variation learn procedure, a switch-over to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switch-over. Perform CKP system variation learn procedure. See «CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__crankshaft-position-sensor-system-variation-learn) under PROGRAMMING. After performing repairs and procedures, go to step 18.
17. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to next step.
18. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

DTC P0125: ECT EXCESSIVE TIME TO ENTER CLOSED LOOP FUEL CONTROL (GASOLINE)

Note. For circuit reference, see WIRING DIAGRAMS article.

Engine Coolant Temperature (ECT) sensor monitors temperature of coolant. This input is used by PCM for engine control and as an enabling criteria for some diagnostics.

Airflow coming into engine is accumulated and used to determine if engine has been driven within conditions that would allow engine coolant to heat up normally to thermostat regulating temperature. If coolant temperature does not increase normally or does not reach regulating temperature of thermostat, diagnostics that use engine coolant temperature as enabling criteria may not run when expected.

This DTC will only run once per ignition cycle within enabling conditions.

This DTC will set when there has been excessive time to reach closed loop fuel control.

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0130, P0131, P0132, P0171, P0172, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0325, P0336, P0420, P0440, P0442, P0446, P0452, P0453, P0480, P0502, P0503, or P1441 are not set.
2. Engine has run more than 30 seconds and less than 20 minutes.
3. Minimum Intake Air Temperature (IAT) is more than 19°F (-7°C).
4. Engine coolant temperature at start up is less than 95°F (35°C).

DTC sets when

1. Average airflow is more than 15 grams per second.
2. Vehicle has traveled more than 0.5 mile at speeds more than 25 MPH.
3. Enough airflow has entered engine, and engine coolant temperature has not risen to 104°F (40°C) for 30 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. If cooling system is low on coolant, repair cooling system as necessary. If cooling system is not low on coolant, go to next step.
3. Turn ignition off. Disconnect ECT sensor. (Scheme 6)or (Scheme 7). Connect fused jumper wire (3-amp) between ECT sensor connector terminals. Turn ignition on, engine off. Using scan tool, observe ECT sensor temperature. If scan tool indicates ECT sensor temperature is more than 280°F (138°C), go to step 7. If scan tool does not indicate ECT sensor temperature is more than 280°F (138°C), go to next step.
4. Turn ignition off. Disconnect ECT sensor. Connect fused jumper wire (3-amp) between ECT sensor connector terminal "B" (Yellow wire) and ground. Turn ignition on, engine off. Using scan tool, observe ECT sensor temperature. If scan tool indicates ECT sensor temperature is more than 280°F (138°C), go to next step. If scan tool does not indicate ECT sensor temperature is more than 280°F (138°C), go to step 6.
5. Repair high resistance or open in Brown wire on "J" body or Black/White wire on "N" body between ECT sensor and PCM. After repair, go to step 10.
6. Repair high resistance or open in Yellow wire between ECT sensor and PCM. After repair, go to step 10.
7. Remove ECT sensor. Suspend the ECT sensor and a thermometer in a pan of water. Place pan on a burner or hot plate. Check resistance of ECT sensor through 50-194°F (10-90°C). See «TEMPERATURE VS RESISTANCE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) table in DTC P0112: IAT SENSOR CIRCUIT - LOW VOLTAGE (2.4L). If resistance and temperature closely match temperature versus resistance table, go to next step. If resistance and temperature do not closely match temperature versus resistance table, go to step 9.
8. Reinstall ECT sensor. Diagnose thermostat in engine cooling system.
9. Replace ECT sensor. After repairs, go to next step.
10. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
11. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

DTC P0125 is designed to detect a skewed ECT sensor or a faulty thermostat.

A skewed IAT sensor may cause this DTC to set. IAT sensor should read near ambient temperature with engine running.

Engine Coolant Temperature (ECT) sensor is a thermistor. ECT sensor has high resistance when cold and low resistance when hot. Powertrain Control Module (PCM) supplies 5 volts and ground to ECT sensor. When ECT resistance is high (cold sensor), ECT signal voltage remains near 5 volts. As ECT sensor warms and resistance drops, signal circuit voltage is pulled low. PCM and Alternate Fuel Control Module (AF ECU) monitor ECT signal circuit voltage to determine engines temperature.

For DTC to run, the following conditions must be met

1. Engine is operating on alternative fuel.
2. AF ECU DTCs P0112, P0113, P0117, P0118 are not set.
3. This DTC has not tested this ignition cycle.
4. Engine has been operating for more than 8.5 minutes.
5. Vehicle speed is more than 5 MPH.
6. Desired gas flow is more than 0.5 grams per second.
7. Intake Air Temperature (IAT) is more than 5°F (-15°C).
8. Engine coolant temperature at engine start-up is 1-91°F (-17°C to 33°C).

DTC will set when AF ECU detects engine coolant temperature that has not increased above start-up temperature by 77°F (25°C).

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Verify thermostat is opening and closing and cooling system is operating properly. Repair as necessary. After repairs, go to step 11. If cooling system is okay, go to next step. NOTE: Additional DTCs may set during next steps. Clear DTCs when diagnosis is complete.
3. Using scan tool, communicate with AF ECU. Disconnect ECT sensor connector. (Scheme 6) If ECT sensor voltage is more than 4.8 volts, go to next step. If ECT sensor voltage is less than 4.8 volts, go to step 7.
4. Monitor ECT sensor voltage. Connect a fused jumper wire between ECT sensor connector terminals "A" (Brown wire) and "B" (Yellow wire). If ECT sensor voltage is more than 0.019 volt, go to next step. If ECT sensor voltage is less than 0.019 volt, go to step 8. WARNING: To avoid being burned, DO NOT remove radiator cap or surge tank cap while engine is hot. Cooling system will release scalding fluid and steam under pressure if radiator cap or surge tank cap is removed while engine and radiator are still hot.
5. Reconnect ECT sensor connector. Install a thermometer in engine cooling system to measure actual coolant temperature. Start engine and allow to idle. Allow engine to operate until ECT sensor temperature on scan tool has stabilized. Compare actual engine coolant temperature with scan tool reading. If temperature reading on scan tool is close to actual coolant temperature, go to next step. If temperature reading on scan tool is not close to actual coolant temperature, go to step 9.
6. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
7. Check for short to ground in Yellow wire between ECT sensor connector terminal "B", PCM connector C1 terminal No. 54 and AF ECU Blue connector C001 terminal No. 12. (Scheme 3)and (Scheme 5). Repair as necessary. After repairs, go to step 11. If circuit is okay, go to step 10.
8. Check for open or high resistance in Yellow wire between ECT sensor connector terminal "B", PCM connector C1 terminal No. 54 and AF ECU Blue connector C001 terminal No. 12. (Scheme 3)and (Scheme 5). Check for open or high resistance in Brown wire between ECT sensor connector terminal "A" and PCM connector C2 terminal No. 27. Check for poor connections at PCM, AF ECU and ECT sensor connectors. Repair as necessary. After repairs, go to step 11. If circuits and connections are okay, go to step 10.
9. Replace ECT sensor. After repairs, go to step 11.
10. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to next step.
11. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Most likely cause of this DTC is an improperly operating engine coolant system and thermostat. Problem may also be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

DTC P0128: ECT LESS THAN THERMOSTAT REGULATING TEMPERATURE

Note. For circuit reference, see WIRING DIAGRAMS article.

Engine Coolant Temperature (ECT) sensor monitors temperature of coolant. This input is used by PCM for engine control, and as an enabling criteria for some diagnostics.

Airflow coming into engine is accumulated and used to determine if engine has been driven within conditions that would allow engine coolant to heat up normally to thermostat regulating temperature. If coolant temperature does not increase normally, or does not reach regulating temperature of thermostat, diagnostics that use engine coolant temperature as enabling criteria, may not run when expected.

DTC will only run once per ignition cycle within enabling conditions.

If engine coolant fails to reach a preset target temperature before a calculated airflow is accumulated, DTC will set.

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0130, P0131, P0132, P0171, P0172, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0325, P0336, P0420, P0440, P0442, P0446, P0452, P0453, P0480, P0502, P0503 (A/T), or P1441 are not set.
2. Engine has run more than 30 seconds and less than 20 minutes.
3. Minimum Intake Air Temperature (IAT) is more than 19°F (-7°C).
4. Engine coolant temperature at start up is less than 149°F (65°C).

DTC sets when

1. Average airflow is more than 15 grams per second.
2. Vehicle has traveled more than 1.5 miles at speeds more than 25 MPH.
3. Enough airflow has entered engine and engine coolant temperature has not risen to 158°F (70°C) for 30 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. If cooling system is low on coolant, repair cooling system as necessary. If cooling system is not low on coolant, go to next step.
3. Turn ignition off. Disconnect ECT sensor. (Scheme 6)or (Scheme 7). Connect fused jumper wire (3-amp) between ECT sensor connector terminals. Turn ignition on, engine off. Using scan tool, observe ECT sensor temperature. If scan tool indicates ECT sensor temperature is more than 280°F (138°C), go to step 7. If scan tool does not indicate ECT sensor temperature is more than 280°F (138°C), go to next step.
4. Turn ignition off. Disconnect ECT sensor. Connect fused jumper wire (3- amp) between ECT sensor connector terminal "B" (Yellow wire) and ground. Turn ignition on, engine off. Using scan tool, observe ECT sensor temperature. If scan tool indicates ECT sensor temperature is more than 280°F (138°C), go to next step. If scan tool does not indicate ECT sensor temperature is more than 280°F (138°C), go to step 6.
5. Repair high resistance or open in Brown wire on "J" body or Black/White wire on "N" body between ECT sensor and PCM. After repair, go to step 10.
6. Repair high resistance or open in Yellow wire between ECT sensor and PCM. After repair, go to step 10.
7. Remove ECT sensor. Suspend the ECT sensor and a thermometer in a pan of water. Place pan on a burner or hot plate. Check resistance of ECT sensor through 50-194°F (10-90°C). See «TEMPERATURE VS RESISTANCE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) table under DTC P0112: IAT SENSOR CIRCUIT - LOW VOLTAGE (2.4L). If resistance and temperature closely match temperature vs resistance table, go to next step. If resistance and temperature do not closely match temperature vs resistance table, go to step 9.
8. Reinstall ECT sensor. Diagnose engine does not reach operating temperature.
9. Replace ECT sensor. After repairs, go to next step.
10. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
11. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

DTC P0128 is designed to detect a faulty thermostat.

Skewed IAT sensor may cause DTC to set. IAT sensor should read near ambient temperature with engine running.

DTC P0130: O2S1 CIRCUIT CLOSED-LOOP PERFORMANCE

Note. For circuit reference, see WIRING DIAGRAMS article.

When vehicle is first started, engine operates in an open loop operation, ignoring oxygen sensor signal and calculating air/fuel ratio based on inputs from Engine Coolant Temperature (ECT), the Throttle Position (TP) and Manifold Absolute Pressure (MAP) sensors only. PCM will begin by using oxygen sensor signal for controlling fuel delivery (closed loop) when the following conditions are met

1. Engine has run a minimum amount of time based on ECT at engine start up.
2. Oxygen Sensor (O2S1) has a varying voltage output showing that it is hot enough to operate properly.
3. ECT has increased a minimum amount based on ECT at engine start up.

1. DTCs P0105, P0107, P0108, P0117, P0118, P0122, P0123, P0125, P0128, P0131, P0132, P0133, P0134, P0171, P0172, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0325, P0336, P0440, P0442, P0446, P0452, P0453, P0502, P0601, P0602, P1133, P1441, or P1621 are not set.
2. Engine has been running more than 100 seconds.
3. Engine speed is between 1200-3400 RPM.
4. TP angle is 10-40 percent.
5. ECT is more than 140°F (60°C).
6. Above conditions have been met for 2 seconds.

DTC sets when engine is not in closed loop for 5 seconds out of 12.5 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, check for DTCs. If any other DTCs are set, diagnose affected DTC(s) first. Start and operate engine at 1200 RPM or more for 2 minutes. Using scan tool, observe O2S voltage parameter. Voltage reading should be varying within a range of 400-500 millivolts. If voltage reading is varying outside of specified value, go to next step. If voltage reading is varying within the specified value, go to step 4 .
3. Operate vehicle within failure records conditions. If scan tool indicates that this DTC failed in this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed in this ignition cycle, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
4. Check for exhaust leaks, improperly installed O2S or damaged sensor wiring. Repair as necessary. After repairs, go to step 13 . If no problems were found, go to next step.
5. Turn ignition off. Disconnect oxygen sensor harness connector. O2S is located in exhaust manifold. Connect jumper wire between O2S connector terminal "A" (Tan wire) and ground. Turn ignition on, with engine off. Using a DVOM, check voltage between chassis ground and O2S connector terminal "B" (Purple wire). If voltage reading is 351-551 millivolts, go to next step. If voltage reading is not 351-551 millivolts, go to step 8
6. Connect a jumper wire between O2S harness connector terminals. Using scan tool, monitor O2S voltage. If voltage reading is about zero millivolt, go to step 9 . If voltage reading is not about zero millivolt, go to next step.
7. Check Tan wire between O2S and PCM for open, high resistance, or short to voltage. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 11 .
8. Check Purple wire between O2S and PCM for open, high resistance or short to voltage. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 11 .
9. Check for poor connections at O2S connectors. Repair as necessary. After repairs, go to step 13 . If connections are okay, go to next step.
10. Check for alcohol contaminated fuel, engine oil or coolant consumption or improper use of RTV sealant, affecting HO2S. Repair cause of contamination and replace O2S. See OXYGEN SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 13 .
11. Check for poor connections at PCM. Repair as necessary. After repairs, go to step 13 . If connections are okay, go to next step.
12. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
13. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
14. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

DTC P0130 or slow response is most likely caused by one of the following conditions

1. Fuel Pressure System will go rich if fuel pressure is too high. PCM can compensate for some increase, however, if it gets too high, a DTC P0172 may set.
2. Leaking Injector Leaking or malfunctioning injector can cause system to go rich.
3. Manifold Absolute Pressure (MAP) Sensor An output that causes PCM to sense a higher than normal manifold pressure (low vacuum) can cause system to go rich. Disconnecting MAP sensor will allow PCM to set a fixed value for MAP sensor. Substitute a different MAP sensor if rich condition is gone while MAP sensor is disconnected.
4. Pressure Regulator Test for a leaking fuel pressure regulator diaphragm by inspecting for presence of liquid fuel in vacuum line to fuel pressure regulator.
5. TP Sensor An intermittent TP sensor output can cause system to go rich due to a false indication of engine accelerating.
6. O2S1 Contamination Inspect O2S1 for silicone contamination from fuel or use of improper RTV sealant. O2S1 sensor may have a White powdery coating and result in a high but false voltage signal, indicating a rich exhaust condition. PCM will then reduce the amount of fuel delivered to the engine, causing a severe surge or driveability problem.

DTC P0131: O2S1 CIRCUIT - LOW VOLTAGE (GASOLINE)

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM supplies a voltage of about 450 millivolts between Oxygen Sensor (O2S1) high signal and low signal circuit. O2S1 varies voltage within a range of about 1000 millivolts if exhaust is rich, down through about 100 millivolts if exhaust is lean.

Sensor is like an open circuit and produces no voltage when less than 600°F (315°C). An open sensor circuit or a cold sensor causes open loop operation.

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set.
2. Engine Coolant Temperature (ECT) is more than 158°F (70°C).
3. Battery voltage is more than 10 volts.
4. Fuel level is more than 10 percent.
5. Engine run time is more than 10 seconds.
6. Engine is operating in closed loop.
7. Throttle Position (TP) angle is 8-50 percent.
8. Manifold Absolute Pressure (MAP) is more than 25 kPa.
9. Engine has been in specified conditions for 4 seconds.

DTC sets when O2S1 voltage is less than 52 millivolts for 125 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Run engine until normal operating temperature is reached. Using scan tool, monitor O2S voltage for sensor that applies to DTC. If O2S voltage measures less than 55 millivolts, go to step 4 . If O2S voltage does not measure less than 55 millivolts, go to next step.
3. DTC is intermittent. If any additional DTCs are stored, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If no additional DTCs are stored, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
4. Turn ignition off. Disconnect O2S sensor. O2S is located in exhaust manifold. Connect jumper wire between O2S connector terminal "A" (Tan wire) and ground. Turn ignition on, engine off. Using DVOM connected to ground, measure voltage on O2S connector terminal "B" (Purple wire) on PCM side. If voltage is 351-551 millivolts, go to next step. If voltage is not 351-551 millivolts, go to step 6 .
5. O2S may be detecting a lean exhaust condition. Check for an exhaust leak between O2S and engine, vacuum leaks, incorrect fuel pressure and lean fuel injectors. Repair as necessary. If problem was found and corrected, go to step 10 . If problem was not found, go to step 7 .
6. Check Purple wire of O2S for short to ground or short to Tan wire between O2S and PCM. If problem was found, repair as necessary. After repairs, go to step 10 . If problem was not found, go to step 9 .
7. Check O2S connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 10 . If problem was not found, go to next step.
8. Replace O2S. See OXYGEN SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 10 .
9. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
10. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
11. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

1. Fuel Pressure System will be lean if pressure is too low. It may be necessary to monitor fuel pressure while driving vehicle at various road speeds and/or loads to confirm.
2. MAP Sensor An output that causes PCM to sense a lower than normal manifold pressure, or high vacuum, can cause system to go lean. Disconnecting MAP sensor will allow PCM to substitute a fixed, or default, value for MAP sensor. If lean condition is gone when MAP sensor is disconnected, see «DTC P0105: MAP/TP SENSOR PERFORMANCE/RANGE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__dtc-p0105-maptp-sensor-performancerange-gasoline) for further diagnosis.
3. Fuel Contamination Water, in even small amounts, near in-tank fuel pump inlet, can be delivered to injector. Water causes a lean exhaust and can set DTC.
4. Sensor Harness O2S1 sensor pigtail may be mis-positioned and contacting exhaust manifold.
5. Engine Misfire A misfiring cylinder will result in unburned oxygen in exhaust, which could cause DTC.
6. Cracked Oxygen Sensor (O2S1) A cracked O2S1 sensor or poor ground at O2S1 sensor could cause DTC.
7. Plugged Fuel Filter A plugged fuel filter can cause a lean condition and cause DTC to set.
8. Plugged Oxygen Sensor (O2S1) A plugged reference port on Oxygen Sensor (O2S1) will indicate a lower then normal voltage output from O2S1 sensor.

Oxygen Sensor (O2S) is used to determine oxygen content of exhaust. Oxygen content of exhaust indicates when engine is operating lean or rich. When engine is operating lean, exhaust will have more oxygen content. Once at operating temperature, O2S will produce a voltage in relation to oxygen content of exhaust. O2S requires an operating temperature of 600°F (360°C) to produce voltage. O2S will produce more voltage when exhaust is rich and less voltage when exhaust is lean. O2S operating voltage range is approximately 0.10 volt (100 mV) to one volt (1000 mV). Powertrain Control Module (PCM) supplies a reference voltage to O2S of approximately 450 mV.

For DTC to run, the following conditions must be met

1. Engine is operating on alternative fuel.
2. Engine speed is more than 500 RPM.
3. Engine coolant temperature is more than 160°F (70°C).
4. AF ECU determines O2S has been at operating temperature for at least 2 minutes. ECT must be more than 104°F (40°C) and calculated mass air flow must be more than 6 grams per second for 2 minutes for AF ECU to determine O2S is at operating temperature.
5. AF ECU is operating in closed loop fuel control.

DTC will set when AF ECU monitors an O2S signal voltage of less than 0.02 volts (20 mV) for 6 continuous seconds.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Start engine and run until operating temperature is reached. Using scan tool, communicate with AF ECU. Observe suspect O2S voltage. If O2S voltage is fixed at less than 20 mV, go to step 5. If O2S voltage is not fixed at less than 20 mV, go to next step.
3. Condition necessary to set DTC is not present at this time. Check for the following conditions: Signal wire intermittently shorted to engine ground or sensor low circuit. Open between engine harness circuit splice and AF ECU connectors. O2S connector water intrusion. Exhaust leak between O2S and engine. Intermittent lean engine condition such as vacuum leaks, incorrect or defective PCV valve or system, incorrect fuel pressure or lean GMS/MCV. Repair as necessary. After repairs, go to step 16. If circuits and components are okay, go to next step.
4. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
5. Ensure engine is at operating temperature. Using scan tool, communicate with PCM. Observe suspect O2S voltage. If O2S voltage is fixed at less than 20 mV, go to next step. If O2S voltage is not fixed at less than 20 mV, go to step 11.
6. Turn ignition off. Disconnect AF ECU connectors. AF ECU is located behind left front fascia, below headlight. Start engine and run until operating temperature is reached. Using scan tool, monitor suspect O2S voltage. If O2S voltage is fixed at less than 20 mV, go to next step. If O2S voltage is not fixed at less than 20 mV, go to step 12.
7. Turn ignition off. Disconnect suspect O2S connector. Turn ignition on. Using scan tool, monitor suspect O2S voltage. If O2S voltage is 351-551 mV, go to next step. If O2S voltage is not 351-551 mV, go to step 9.
8. O2S my be detecting a lean condition. Check for and exhaust leak between O2S and engine, vacuum leaks, water intrusion into O2S connector or incorrect or defective PCV valve or system. Repair as necessary. After repairs, go to step 16. If no problems are found, go to step 14.
9. Turn ignition off. Disconnect PCM connectors. PCM is located inside right front fender. Using DVOM, measure resistance between ground and O2S connector terminal "B" (Purple wire). Also measure resistance between O2S connector terminals "A" (Tan wire) and "B" (Purple wire). No resistance should be measured for either measurement. If any resistance is measured for either test, go to next step. If no resistance is measured for both tests, go to step 15.
10. Repair short to ground or short to low reference circuit (Tan wire) in Purple wire between O2S, PCM connector C2 terminal No. 22 and AF ECU White/Clear connector C002 terminal No. 4. (Scheme 3)and (Scheme 5). After repairs, go to step 16.
11. Using DVOM, check for continuity in Purple wire between O2S connector terminal "B", PCM connector C2 terminal No. 22 and AF ECU White/Clear connector C002 terminal No. 4. (Scheme 3)and (Scheme 5). Also check for continuity in Tan wire between O2S connector terminal "A", PCM connector C2 terminal No. 21 and AF ECU White/Clear connector C002 terminal No. 5. Check for poor connections at AF ECU, O2S and PCM. Repair as necessary. After repairs, go to step 16. If circuits and connections are okay, go to step 13.
12. O2S may only be detecting lean condition during alternate fuel (CNG) operation. Perform fuel system diagnosis. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS (2.2L - CAVALIER CNG) in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article. Repair as necessary. After repairs, go to step 16. If fuel system diagnosis passes, go to next step.
13. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to step 16.
14. Replace suspect O2S. See REMOVAL, OVERHAUL & INSTALLATION - CARS article. After repairs, go to step 16.
15. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) PCM with correct vehicle software and calibration. See «POWERTRAIN CONTROL MODULE REPROGRAMMING»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-control-module-reprogramming) under PROGRAMMING. To perform CKP variation learn procedure, a switch-over to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switch-over. Perform CKP system variation learn procedure. See «CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__crankshaft-position-sensor-system-variation-learn) under PROGRAMMING. After performing repairs and procedures, go to next step.
16. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may also be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

DTC P0132: O2S1 CIRCUIT - HIGH VOLTAGE (GASOLINE)

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM supplies a voltage of about 0.45 volt between Oxygen Sensor (O2S1) high signal and low signal circuit. O2S1 varies voltage within a range of about one volt if exhaust is rich, down through about 0.10 volt if exhaust is lean.

Sensor is like an open circuit and produces no voltage when less than 600°F (315°C). An open sensor signal circuit or a cold sensor causes open loop operation.

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set.
2. Engine Coolant Temperature (ECT) is more than 158°F (70°C).
3. Battery voltage is more than 10 volts.
4. Fuel level is more than 10 percent.
5. Engine run time is more than 10 seconds.
6. Engine is operating in closed loop.
7. Throttle Position (TP) angle is 8-50 percent.
8. Manifold Absolute Pressure (MAP) sensor is more than 25 kPa.
9. Engine has met specified conditions for 4 seconds.

DTC sets when O2S1 voltage is more than 946 millivolts for 50 seconds, or O2S1 voltage is more than 1042 millivolts for 50 seconds while in deceleration mode.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Operate vehicle within code enable criteria. Using scan tool, monitor O2S voltage for sensor that applies to this DTC. If O2S voltage is more than 976 millivolts, go to step 4 . If O2S voltage is not more than 976 millivolts, go to next step.
3. DTC is intermittent. If any additional DTCs are stored, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If no additional DTCs are stored, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
4. Turn ignition off. Disconnect O2S sensor. O2S is located in exhaust manifold. Connect jumper wire between O2S connector terminal "A" (Tan wire) and ground. Turn ignition on, engine off. Using DVOM connected to ground, measure voltage on O2S connector terminal "B" (Purple wire) on PCM side. If voltage is 351-551 millivolts, go to next step. If voltage is not 351-551 millivolts, go to step 6 .
5. O2S is detecting a rich exhaust condition or may be contaminated. Check for O2S connector water intrusion, silicone-contaminated O2S, fuel-contaminated engine oil, incorrect fuel pressure, leaking fuel pressure regulator and rich fuel injectors. Repair as necessary. If problem was found and corrected, go to step 10 . If problem was not found, go to step 7 .
6. Check Purple wire between O2S and PCM for short to voltage. If problem was found, repair as necessary. After repairs, go to step 10 . If problem was not found, go to step 9 .
7. Check O2S sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 10 . If problem was not found, go to next step.
8. Before replacing a contaminated O2S, determine and repair cause of contamination. Replace O2S. See OXYGEN SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 10 .
9. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
10. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
11. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

Rich exhaust is most likely caused by one of the following items

1. Fuel Pressure System will go rich if fuel pressure is too high. PCM can compensate for some increase, however, if it gets too high, a DTC P0172 will be set. See «DTC P0172: FUEL TRIM SYSTEM RICH»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__dtc-p0172-fuel-trim-system-rich) .
2. Leaking Injector A leaking or malfunctioning injector can cause system to go rich causing DTC to set.
3. Electronic Ignition (EI) Shielding Open ICM reference low circuit may result in an EMI or induced electrical noise. PCM looks at this noise as crankshaft position (CKP) sensor pulses. Additional pulses result in a higher than actual engine speed signal. PCM then delivers too much fuel, causing system to go rich. Engine tachometer will also show higher than actual engine speed which can help in diagnosing this problem.
4. MAP Sensor An output that causes PCM to sense a higher than normal manifold pressure, or a low vacuum, can cause system to go rich. Disconnecting MAP sensor electrical connector will allow PCM to set a fixed value for MAP sensor. Substitute a different MAP sensor if rich condition is gone while MAP sensor is disconnected.
5. Pressure Regulator Check for leaking fuel pressure regulator diaphragm by checking for presence of liquid fuel in vacuum line to fuel pressure regulator.
6. TP Sensor An intermittent TP sensor output will cause system to go rich due to a false indication of engine accelerating.
7. O2S1 Contamination Inspect O2S1 sensor for silicone contamination from fuel or use of improper RTV sealant. O2S1 sensor may have a white powdery coating and this will result in a high but false voltage signal, indicating a rich exhaust. PCM will then reduce amount of fuel delivered to engine causing a severe surge or driveability problem.

Oxygen Sensor (O2S) is used to determine oxygen content of exhaust. Oxygen content of exhaust indicates when engine is operating lean or rich. When engine is operating lean, exhaust will have more oxygen content. Once at operating temperature, O2S will produce a voltage in relation to oxygen content of exhaust. O2S requires an operating temperature of 600°F (360°C) to produce voltage. O2S will produce more voltage when exhaust is rich and less voltage when exhaust is lean. O2S operating voltage range is approximately 0.10 volt (100 mV) to one volt (1000 mV). Powertrain Control Module (PCM) supplies a reference voltage to O2S of approximately 450 mV.

For DTC to run, the following conditions must be met

1. Engine is operating on alternative fuel.
2. Engine speed is more than 500 RPM.
3. Engine coolant temperature is more than 160°F (70°C).
4. AF ECU determines O2S has been at operating temperature for at least 2 minutes. Engine coolant temperature must be more than 104°F (40°C) and calculated mass air flow must be more than 6 grams per second for 2 minutes for AF ECU to determine O2S is at operating temperature.
5. AF ECU is operating in closed loop fuel control.

DTC will set when AF ECU senses O2S signal voltage of more than one volt (1000 mV) for continuous 3 seconds. When DTC is set, AF ECU will operate in open loop fuel control.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Start engine and run until operating temperature is reached. Using scan tool, communicate with AF ECU. Observe suspect O2S voltage. If O2S voltage is fixed at more than one volt, go to step 5. If O2S voltage is not fixed at more than one volt, go to next step.
3. Condition necessary to set DTC is not present at this time. Check for the following conditions: Signal wire intermittently shorted to voltage. O2S connector water intrusion. Silicon contaminated O2S. An intermittent rich engine condition such as EVAP canister purge system malfunction, gasoline contaminated engine oil, incorrect fuel pressure, leaking gasoline fuel pressure regulator or rich GMS/MCV. Repair as necessary. After repairs, go to step 15. If circuits and components are okay, go to next step.
4. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
5. Ensure engine is at operating temperature. Using scan tool, communicate with PCM. Observe suspect O2S voltage. If O2S voltage is fixed at more than one volt, go to next step. If O2S voltage is not fixed at more than one volt, go to step 12.
6. Turn ignition off. Disconnect AF ECU connectors. AF ECU is located behind left front fascia, below headlight. Start engine and run until operating temperature is reached. Monitor suspect O2S voltage on scan tool. If O2S voltage is fixed at more than one volt, go to next step. If O2S voltage is not fixed at more than one volt, go to step 11.
7. Turn ignition off. Disconnect O2S connector. Turn ignition on. Monitor suspect O2S voltage on scan tool. If O2S voltage is 351-551 mV, go to next step. If O2S voltage is not 351-551 mV, go to step 9.
8. O2S is detecting a rich exhaust condition. Check for O2S connector water intrusion, silicon contaminated O2S, EVAP canister purge system malfunction, gasoline contaminated engine oil, incorrect fuel pressure or leaking gasoline fuel pressure regulator. Repair as necessary. After repairs, go to step 15. If system and components are okay, go to step 13.
9. Turn ignition off. Disconnect PCM connectors. PCM is located inside right front fender. Turn ignition on. Using DVOM, measure voltage between ground and O2S connector terminal "B" (Purple wire). If voltage is more than 20 mV, go to next step. If voltage is less than 20 mV, go to step 14.
10. Repair short to voltage in Purple wire between O2S, PCM connector C2 terminal No. 22 and AF ECU White/Clear connector C002 terminal No. 4. (Scheme 3)and (Scheme 5). After repairs, go to step 15.
11. O2S may only be detecting a rich condition during alternate fuel (CNG) operation. Perform fuel system diagnosis. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS (2.2L - CAVALIER CNG) in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article. Repair as necessary. After repairs, go to step 15. If fuel system is okay, go to next step.
12. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to step 15.
13. Replace suspect O2S. See REMOVAL, OVERHAUL & INSTALLATION - CARS article. After repairs, go to step 15.
14. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) PCM with correct vehicle software and calibration. See «POWERTRAIN CONTROL MODULE REPROGRAMMING»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-control-module-reprogramming) under PROGRAMMING. To perform CKP variation learn procedure, a switch-over to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switch-over. Perform CKP system variation learn procedure. See «CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__crankshaft-position-sensor-system-variation-learn) under PROGRAMMING. After performing repairs and procedures, go to next step.
15. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may also be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

DTC P0133: O2S1 CIRCUIT - SLOW RESPONSE (2.2L - GASOLINE)

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM continuously monitors Oxygen Sensor (O2S1) activity for 100 seconds. During monitoring period, PCM counts number of times O2S1 switches from rich to lean, and from lean to rich, then adds time O2S1 took to complete all switches. With this information, an average time for all switches can be determined. Whenever average time to switch is too slow, a DTC P0133 will set.

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201-P0204, P0300, P0301-P0304, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set.
2. Engine coolant temperature is more than 158°F (70°C).
3. Battery voltage is more than 10 volts.
4. Fuel level is more than 10 percent.
5. Engine run time is more than 10 seconds.
6. Engine speed is between 1600-2450 RPM.
7. Engine is operating in closed loop.
8. Throttle Position (TP) angle is 9-18 percent.
9. Evaporative emissions control system is commanded open more than 36 percent.
10. Purge learned memory is more than approximately 0.78.
11. Diagnostic completes when 30 seconds of accumulated time has been spent in specified conditions.

DTC sets when average O2S1 response times are more than 1119 milliseconds for rich to lean sweeps, or 760 milliseconds for lean to rich sweeps. Or sum of rich to lean and lean to rich is more than 1235 milliseconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. If any other DTCs are set (except O2S DTCs), refer to other DTCs before proceeding with this procedure. Ensure engine is at operating temperature. Operate engine at speeds more than 1200 RPM for 2 minutes. Using scan tool, observe O2S voltage parameter. If scan tool indicates O2S voltage varying outside 400-500 millivolts, go to next step. If scan tool does not indicate O2S voltage varying outside 400-500 millivolts, go to step 4 .
3. If any powertrain component DTCs are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If no powertrain component DTCs are set, go to step 5 .
4. O2S sensor has been contaminated. Contamination source must be removed prior to operating engine with replacement sensor. Possible sources of contamination include use of an incorrect silicone RTV sealant, engine coolant leakage into combustion chamber, excessive engine oil consumption, use of silicone-contaminated fuel and use of fuel containing lead. Replace O2S sensor. See OXYGEN SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 14 .
5. Using scan tool, record DTC information from PCM. Clear DTC information from PCM. Reset fuel trim values. Start and idle engine until normal operating temperature is reached. Operate engine to meet code enable criteria. If DTC ran and failed in this ignition cycle, go to step 7 . If DTC did not run and fail in this ignition cycle, go to next step.
6. DTC is intermittent. If any additional DTCs are stored, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If no additional DTCs are stored, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
7. Check exhaust system for leaks between O2S and engine. Repair exhaust as necessary. Check O2S and PCM connector for poor connections. Repair connectors as necessary. If problem was found and corrected, go to step 15 . If problem was not found, go to next step.
8. Turn ignition off. Disconnect O2S sensor. O2S is located in exhaust manifold. Connect jumper wire between O2S connector terminal "A" (Tan wire) and ground. Turn ignition on, engine off. Using DVOM connected to ground, measure voltage on O2S connector (Purple wire) on PCM side. If voltage is 351-551 millivolts, go to next step. If voltage is not 351-551 millivolts, go to step 11 .
9. Turn ignition off. Connect jumper wire between O2S connector terminal "B" (Purple wire) and ground. Turn ignition on. Using scan tool, monitor O2S voltage for sensor that applies to this DTC. If O2S voltage is less than 20 millivolts, go to next step. If O2S voltage is not less than 20 millivolts, go to step 12 .
10. Check for contamination sources that may have caused O2S to fail. O2S contamination sources include use of an incorrect RTV silicone engine sealant, contaminated fuel and excessive engine oil or coolant consumption. Repair or remove source of contamination. After repairs, go to step 13 .
11. Repair short between Purple wire and Tan wire or between Purple wire and voltage source between O2S and PCM. After repairs, go to step 15 .
12. Repair open or high circuit resistance in Purple wire or Tan wire between O2S and PCM. After repairs, go to step 15 .
13. Check O2S sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 15 . If problem was not found, go to next step.
14. Replace O2S. See OXYGEN SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
15. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
16. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

DTC P0133 or slow response is most likely caused by one of the following conditions

1. Fuel Pressure System will go rich if fuel pressure is too high. PCM can compensate for some increase, but if fuel pressure becomes too high, DTC P0172 may set. See «DTC P0172: FUEL TRIM SYSTEM RICH»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__dtc-p0172-fuel-trim-system-rich) .
2. Leaking Injector Leaking or malfunctioning injector can cause system to go rich.
3. Manifold Absolute Pressure (MAP) Sensor An output that causes PCM to sense a higher than normal manifold pressure, or a low vacuum, can cause system to go rich. Disconnecting MAP sensor will allow PCM to set a fixed value for MAP sensor. Substitute a different MAP sensor if rich condition is gone while MAP sensor is disconnected.
4. Pressure Regulator Check for a leaking fuel pressure regulator diaphragm by confirming presence of liquid fuel in vacuum line to fuel pressure regulator.
5. Throttle Position (TP) Sensor An intermittent TP sensor output can cause system to go rich due to a false indication of engine accelerating.
6. O2S1 Contamination Inspect O2S1 for silicone contamination from fuel or from use of an improper room-temperature vulcanizing (RTV) sealant. O2S1 sensor may have a White powdery coating which will result in a high but false voltage signal, indicating a rich exhaust. PCM will then reduce amount of fuel delivered to engine, causing a severe surge or driveability problem.

This DTC tests the Powertrain Control Module (PCM) and NOT the Alternative Fuels Engine Control Unit (AF ECU). PCM continuously monitors oxygen sensor 1 (O2S 1) activity for 100 seconds. During monitoring period, PCM counts the number of times O2S 1 switches rich to lean, and lean to rich, then adds time O2S 1 took to complete all switches. With this information, an average time for all switches can be determined.

For DTC to run, the following conditions must be met

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0506, P0507, P0601 are not set.
2. Engine is operating on alternative fuel.
3. Engine Coolant Temperature (ECT) is more than 167°F (75°C).
4. Engine speed is 1600-2200 RPM.
5. Engine is operating in closed loop.
6. Engine has been operating for at least 120 seconds with engine speed of more than 450 RPM.
7. Throttle Position (TP) angle is 9-23 percent.
8. TP angle changes less than 3 percent per second.
9. Evaporative emissions control system is commanded open for more than 80 percent.
10. Purge learned memory is more than approximately 0.86.
11. Diagnostic completes when 30 seconds of accumulated time has been spent in the above conditions.

DTC will set when average O2S 1 response times are more than 1174 milliseconds (mS) for rich to lean sweeps, or 1008 mS for lean to rich sweeps. DTC will also set when cycle time is more than 1491 mS.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Start engine and allow to idle until normal operating temperature is reached. Operate vehicle within specifications to run DTC. See «CODE ENABLE CRITERIA»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l). Using scan tool, monitor lean/rich switching average, rich/lean switching average and rich/lean to lean/rich ratio. If averages are more than those listed in code enable criteria, go to step 4. If averages are equal to or less than those listed in code enable criteria, go to next step.
3. If any additional powertrain DTCs are set, diagnose those DTCs first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions). If no additional powertrain DTCs are set, go to step 5.
4. O2S is contaminated, replace O2S. Before replacing O2S, repair source of contamination such as engine coolant in combustion chamber, silicon contaminated O2S, EVAP canister purge system malfunction, gasoline contaminated engine oil, incorrect fuel pressure or leaking gasoline fuel pressure regulator.
5. Using scan tool, record DTC data. Clear DTCs. Communicate with AF ECU and reset fuel trim values. Start engine and allow to idle until normal operating temperature is reached. Operate vehicle within specifications to run DTC. See «CODE ENABLE CRITERIA»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l). Recheck for DTCs. If DTC resets this ignition, go to step 7. If DTC does not reset this ignition, go to next step.
6. This DTC is intermittent. If any additional DTCs are set, diagnose those DTCs first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions). If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
7. Check for exhaust leaks between engine and O2S. Check for poor connections at O2S connector. Repair as necessary. After repairs, go to step 13. If exhaust and O2S connections are okay, go to next step.
8. Turn ignition off. Disconnect O2S connector. Turn ignition on. Using scan tool, monitor O2S voltage for suspect sensor. If O2S voltage is 351-551 mV, go to next step. If voltage is not 351-551 mV, go to step 11.
9. Turn ignition off. Connect fused jumper between O2S connector terminal "B" (Purple wire) and ground. Turn ignition on. Using scan tool, monitor O2S voltage for suspect sensor. If O2S voltage is less than 20 mV, go to next step. If voltage is more than 20 mV, go to step 12.
10. Repair contamination that would cause O2S to fail. Check for RTV silicone sealant, contaminated fuel or excessive oil or engine coolant consumption. After repairs, go to step 13.
11. Repair short between O2S Purple wire between O2S connector terminal "B", PCM connector C2 terminal No. 22 and AF ECU White/Clear connector C002 terminal No. 4 and Tan wire between O2S connector terminal "A", PCM connector C2 terminal No. 21 and AF ECU White/Clear connector C002 terminal No. 5. (Scheme 3)and (Scheme 5). If short between circuits is not present, repair short to voltage in Purple wire. After repairs, go to step 14.
12. Repair for open or high resistance in Purple wire between O2S connector terminal "B", PCM connector C2 terminal No. 22 and AF ECU White/Clear connector C002 terminal No. 4 and Tan wire between O2S connector terminal "A", PCM connector C2 terminal No. 21 and AF ECU White/Clear connector C002 terminal No. 5. (Scheme 3)and (Scheme 5). After repairs, go to step 14.
13. Replace O2S. After repairs, go to next step.
14. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and allow it to reach normal operating temperature. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, go to step 2.
15. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions). If no undiagnosed DTCs are displayed, system is okay.

DTC P0133 or slow response is most likely caused by one of the following conditions

1. MAP sensor output that causes PCM to sense a higher than normal manifold pressure, or low vacuum, can cause system to go rich. Disconnecting MAP sensor will allow PCM to set a fixed value for MAP sensor. Substitute a different MAP sensor if rich condition is gone while MAP sensor is disconnected.
2. An intermittent TP sensor output can cause system to go rich due to a false indication of engine accelerating.
3. Check O2S 1 for silicone contamination from fuel or from use of an improper Room Temperature Vulcanizing (RTV) sealant. O2S 1 sensor may have a white powdery coating which will result in high but false voltage signal, indicating rich exhaust. PCM will then reduce amount of fuel delivered to engine, causing a severe surge or driveability problem.

DTC P0133: O2S1 CIRCUIT - SLOW RESPONSE (2.4L)

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM continuously monitors oxygen sensor (O2S1) activity for 100 seconds. During monitor period, PCM counts number of times that O2S1 switches from rich to lean and from lean to rich and adds amount of time that O2S1 took in order to complete all of switches. With this information, you can determine an average time for all of the switches. If average time to switch is too slow, a DTC P0133 will set.

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set.
2. Fuel level is more than 10 percent.
3. Engine Coolant Temperature (ECT) is more than 158°F (70°C).
4. Engine speed is between 1600 RPM and 2450 RPM.
5. Engine is operating in closed loop.
6. Throttle Position (TP) angle is 9-18 percent.
7. Evaporative emissions control system is commanded OPEN more than 36 percent.
8. Purge learned memory is more than approximately 0.78.
9. Diagnostic completes when 30 seconds accumulated time has been spent in specified conditions.

DTC sets when average O2S1 response times are more than 1119 milliseconds for rich to lean sweeps or 760 milliseconds for lean to rich sweeps. Or sum of rich to lean and lean to rich is more than 1235 milliseconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. If any other DTCs are set (except O2S DTCs), refer to other DTCs before proceeding with this procedure. Ensure engine is at operating temperature. Operate engine at speeds more than 1200 RPM for 2 minutes. Using scan tool, observe O2S voltage parameter. If scan tool indicates HO2S voltage varying outside 400-500 millivolts, go to next step. If scan tool does not indicate HO2S voltage varying outside 400-500 millivolts, go to step 4 .
3. Operate vehicle within failure records conditions. If scan tool indicates this DTC failed this ignition cycle, go to next step. If scan tool does not indicate this DTC failed this ignition cycle, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
4. Inspect and test for exhaust leak, O2S installed correctly and damaged wiring. If problem was found, repair as necessary. After repairs, go to step 13 . If problem was not found, go to next step.
5. Turn ignition off. Disconnect O2S sensor. O2S is located in exhaust manifold. Connect jumper wire between O2S connector terminal "A" (Tan wire) and ground. Turn ignition on, engine off. Using DVOM connected to ground, measure voltage on O2S connector terminal "B" (Purple wire) on PCM side. If voltage is 351-551 millivolts, go to next step. If voltage is not 351-551 millivolts, go to step 8 .
6. Connect jumper wire between O2S connector terminals. Using scan tool, observe O2 VOLTAGE parameter. If scan tool indicates O2 voltage at or near zero millivolts, go to step 9 . If scan tool does not indicate O2 voltage at or near zero millivolts, go to next step.
7. Check Tan wire between O2S and PCM for open or high resistance. If problem was found, repair as necessary. After repairs, go to step 13 . If problem was not found, go to step 11 .
8. Check Purple wire between O2S and PCM for open or high resistance. If problem was found, repair as necessary. After repairs, go to step 13 . If problem was not found, go to step 11 .
9. Check O2S connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 13 . If problem was not found, go to next step.
10. O2S sensor has been contaminated. Contamination source must be removed prior to operating engine with replacement sensor. Possible sources of contamination include use of an incorrect silicone RTV sealant, engine coolant leakage into combustion chamber, excessive engine oil consumption, use of silicone-contaminated fuel and use of fuel containing lead. Replace O2S sensor. See OXYGEN SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 13 .
11. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 13 . If problem was not found, go to next step.
12. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
13. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
14. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

DTC P0133 or slow response is most likely caused by one of the following items

1. Fuel Pressure System will go rich if fuel pressure is too high. PCM can compensate for some increase, however, if it gets too high, a DTC P0172 may set. See «DTC P0172: FUEL TRIM SYSTEM RICH»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__dtc-p0172-fuel-trim-system-rich) .
2. Leaking Injector Leaking or malfunctioning injector can cause system to go rich.
3. Manifold Absolute Pressure (MAP) Sensor An output that causes PCM to sense a higher than normal manifold pressure (low vacuum) can cause system to go rich. Disconnecting MAP sensor will allow PCM to set a fixed value for MAP sensor. Substitute a different MAP sensor if rich condition is gone while MAP sensor is disconnected.
4. Pressure Regulator Check for a leaking fuel pressure regulator diaphragm by checking for the presence of liquid fuel in vacuum line to fuel pressure regulator.
5. TP Sensor An intermittent TP sensor output can cause system to go rich due to a false indication of engine accelerating.
6. O2S1 Contamination Inspect O2S1 for silicone contamination from fuel or use of improper room temperature vulcanizing (RTV) sealant. O2S1 sensor may have a White powdery coating and result in a high but false voltage signal (rich exhaust indication). PCM will then reduce amount of fuel delivered to engine causing a severe surge or driveability problem.

DTC P0134: O2S1 CIRCUIT - INSUFFICIENT ACTIVITY (GASOLINE)

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM supplies a voltage of about 450 millivolts between Oxygen Sensor (O2S1) high signal and low signal circuit. O2S1 varies voltage within a range of about 1000 millivolts if exhaust is rich, down through about 100 millivolts if exhaust is lean.

Sensor is like an open circuit and produces no voltage when less than 600°F (315°C). An open sensor signal circuit or a cold sensor causes an open loop operation.

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set.
2. Battery voltage is more than 10 volts.
3. Fuel level is more than 10 percent.
4. Engine coolant temperature is more than 158°F (70°C).
5. Airflow is more than 3 grams per second.
6. Throttle Position (TP) angle is 8-56 percent.
7. Manifold Absolute Pressure (MAP) is more than 25 kPa.
8. Engine run time is more than 30 seconds.

DTC sets when O2S1 voltage is 399-499 millivolts for 125 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. If any other DTCs are set (except O2S DTCs), refer to other DTCs before proceeding with this procedure. Ensure engine is at operating temperature. Operate engine at more than 1200 RPM for 2 minutes. Using scan tool, observe O2S voltage parameter. If scan tool indicates O2S voltage varying outside 400-500 millivolts, go to next step. If scan tool does not indicate HO2S voltage varying outside 400-500 millivolts, go to step 4 .
3. Operate vehicle within failure records conditions. If scan tool indicates this DTC failed this ignition cycle, go to next step. If scan tool does not indicate this DTC failed this ignition cycle, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
4. Inspect and test for exhaust leak, O2S installed correctly and damaged wiring. If problem was found, repair as necessary. After repairs, go to step 13 . If problem was not found, go to next step.
5. Turn ignition off. Disconnect O2S sensor. O2S in located in exhaust manifold. Connect jumper wire between O2S connector terminal "A" (Tan wire) and ground. Turn ignition on, engine off. Using DVOM connected to ground, measure voltage on O2S connector terminal "B" (Purple wire) on PCM side. If voltage is 351-551 millivolts, go to next step. If voltage is not 351-551 millivolts, go to step 8 .
6. Connect jumper wire between O2S connector terminals. Using scan tool, observe O2 VOLTAGE parameter. If scan tool indicates O2 voltage at or near zero millivolts, go to step 9 . If scan tool does not indicate O2 voltage at or near zero millivolts, go to next step.
7. Check Tan wire between O2S and PCM for open, high resistance or short to voltage. If problem was found, repair as necessary. After repairs, go to step 13 . If problem was not found, go to step 11 .
8. Check Purple wire between O2S and PCM for open, high resistance or short to voltage. If problem was found, repair as necessary. After repairs, go to step 13 . If problem was not found, go to step 11 .
9. Check O2S connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 13 . If problem was not found, go to next step.
10. O2S sensor has been contaminated. Contamination source must be removed prior to operating engine with replacement sensor. Possible sources of contamination include use of an incorrect silicone RTV sealant, engine coolant leakage into combustion chamber, excessive engine oil consumption, use of silicone-contaminated fuel and use of fuel containing lead. Replace O2S sensor. See OXYGEN SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 13 .
11. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 13 . If problem was not found, go to next step.
12. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
13. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
14. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

Check oxygen sensor pigtail wire for breaks, contamination or grounding on exhaust manifold. Check for intermittent ground in signal wire between sensor connector and sensor. DO NOT attempt to repair damaged oxygen sensor connector or wiring. If damage is detected, replace oxygen sensor.

Oxygen Sensor (O2S) is used to determine oxygen content of exhaust. Oxygen content of exhaust indicates when engine is operating lean or rich. When engine is operating lean, exhaust will have more oxygen content. Once at operating temperature, O2S will produce a voltage in relation to the oxygen content of the exhaust. O2S requires an operating temperature of 600°F (360°C) to produce voltage. O2S will produce more voltage when exhaust is rich and less voltage when exhaust is lean. O2S operating voltage range is 0.1-1 volt (100-1000 mV).

Powertrain Control Module (PCM) supplies a reference voltage to O2S. This reference voltage is around 450 mV. Alternate Fuel Engine Control Unit (AF ECU) monitors reference voltage as well as voltage produced by O2S.

During normal closed loop fuel control operation, AF ECU will add fuel (enriches mixture) when O2S indicates a lean exhaust condition. When O2S indicates a rich exhaust content, AF ECU will subtract fuel (lean-out mixture). This oscillation above and below reference voltage (sometimes referred to as activity or switching) can be monitored using O2S signal voltage.

For DTC to run, the following conditions must be met

1. Engine is operating on alternative fuel.
2. Engine speed is more than 500 RPM.
3. Engine has been operating for at least 2 minutes.
4. AF ECU determines O2S has been at operating temperature for at least 2 minutes.
5. Engine coolant temperature must be more than 104°F (40°C) and calculated mass air flow must be more than 6 grams per second for 2 minutes for AF ECU to determine O2S is at operating temperature.

DTC will set when AF ECU detects an O2S signal voltage stuck between 0.347 volt and 0.550 volt (in-active) for 9 continuous seconds or AF ECU detects an O2S signal voltage between zero and one volt that has not performed a rich/lean switch for 15 continuous seconds. When DTC is set, AF ECU will operate in open loop fuel control.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Using scan tool, communicate with AF ECU. Record DTC data, clear DTCs and reset fuel trim values. Start engine and allow to idle until normal operating temperature is reached. Using scan tool, monitor suspect O2S voltage. If O2S voltage is fixed between zero and one volt, go to step 5. If O2S voltage is not fixed between zero and one volt, go to next step.
3. Conditions necessary to set DTC are not present at this time. Check for intermittents open or high resistance in Purple wire between O2S connector terminal "B", PCM connector C2 terminal No. 22 and AF ECU White/Clear connector C002 terminal No. 4 and Tan wire between O2S connector terminal "A", PCM connector C2 terminal No. 21 and AF ECU White/Clear connector C002 terminal No. 5. (Scheme 3)and (Scheme 5). Check for poor connections at PCM, AF ECU and O2S. Check for high resistance in AF ECU ground circuits. Check for an exhaust leak approximately 12" upstream from O2S. Repair as necessary. After repairs, go to step 16. If connections, components and circuits are okay, go to next step.
4. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
5. Start engine and allow to idle until normal operating temperature is reached. Using scan tool, communicate with AF ECU. Using scan tool, select special functions and force a switch over to gasoline. Communicate with PCM. Verify engine is operating in closed loop fuel control. Monitor suspect O2S voltage. If O2S voltage is fixed between zero and one volt, go to next step. If O2S voltage is not fixed between zero and one volt, go to step 11.
6. Turn ignition off. Disconnect suspect O2S connector. Connect a fused jumper between negative battery terminal and O2S connector terminal "B" (Purple wire). Turn ignition on. Monitor suspect O2S voltage. If O2S voltage is less than 20 mV, go to step 10. If O2S voltage is more than 20 mV, go to next step.
7. Turn ignition off. Remove fused jumper wire. Disconnect PCM connectors. PCM is located inside right front fender. Using DVOM, measure resistance of Purple wire between O2S connector terminal "B" and PCM connector C2 terminal No. 22. (Scheme 5) Also measure resistance of Tan wire between O2S connector terminal "A" and PCM connector C2 terminal No. 21. If resistance for both circuits is less than 5 ohms, go to next step. If resistance in either circuit is more than 5 ohms, go to step 9.
8. Check for poor connections at PCM. Repair as necessary. After repairs, go to step 16. If connections are okay, go to step 15.
9. Repair open or high resistance in circuit that measured more than 5 ohms. After repairs, go to step 16.
10. Check for exhaust leaks approximately 12" upstream of O2S. Repair as necessary. After repairs, go to step 16. If exhaust is okay, go to step 13.
11. Turn engine off. Disconnect O2S, PCM and AF ECU connectors. PCM is located inside right front fender. AF ECU is located behind left front fascia, below headlight. Using DVOM, check for continuity in Purple wire between O2S connector terminal "B" and AF ECU White/Clear connector C002 terminal No. 4 and Tan wire between O2S connector terminal "A" and AF ECU White/Clear connector C002 terminal No. 5. (Scheme 3) Repair as necessary. After repairs, go to step 16. If circuits are okay, go to next step.
12. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to step 16.
13. Perform fuel system diagnosis then return to this test step. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS (2.2L - CAVALIER CNG) in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article. If fuel system problem is found and repaired, go to step 15. If fuel system problem is not found and repaired, go to next step.
14. Replace O2S. After repairs, go to step 16.
15. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) PCM with correct vehicle software and calibration. See «POWERTRAIN CONTROL MODULE REPROGRAMMING»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-control-module-reprogramming) under PROGRAMMING. To perform CKP variation learn procedure, a switch-over to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switch-over. Perform CKP system variation learn procedure. See «CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__crankshaft-position-sensor-system-variation-learn) under PROGRAMMING. After performing repairs and procedures, go to next step.
16. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may also be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

DTC P0137: HO2S2 CIRCUIT - LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article.

In order to control emissions, a catalytic converter converts any harmful exhaust emissions into harmless water vapor and carbon dioxide.

PCM has capability to monitor this process by using a rear heated oxygen sensor (HO2S2). HO2S2 , located in exhaust stream past catalytic converter, produces an output signal which indicates storage capacity of catalyst. This in turn indicates catalysts ability to convert exhaust emissions effectively. If catalyst is functioning properly, HO2S2 signal will be far less active than signal produced by front oxygen sensor (O2S1).

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set.
2. Engine coolant temperature (ECT) is more than 158°F (70°C).
3. Battery voltage is more than 10 volts.
4. Engine run time is more than 10 seconds.
5. Throttle Position (TP) angle is 8-50 percent for 4 seconds.
6. Manifold Absolute Pressure (MAP) is more than 25 kPa.

DTC sets when HO2S2 remains less than 43 millivolts for 150 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Run engine until normal operating temperature is reached. Using scan tool, monitor HO2S voltage for sensor that applies to this DTC. If HO2S voltage is less than 26 millivolts, go to step 4. If HO2S voltage is not less than 26 millivolts, go to next step.
3. DTC is intermittent. If any additional DTCs are stored, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions). If no additional DTCs are stored, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Disconnect HO2S sensor. HO2S is located in exhaust stream past catalytic converter. Connect jumper wire between HO2S connector terminal "A" (Tan/White wire) and ground. (Scheme 10) Turn ignition on, engine off. Using DVOM connected to ground, measure voltage on HO2S connector terminal "B" (Purple/White wire) on PCM side. If voltage is 351-551 millivolts, go to next step. If voltage is not 351-551 volts, go to step 6.
5. HO2S may be detecting a lean exhaust condition. Check for one of the following conditions: HO2S connector water intrusion. An exhaust leak between HO2S and engine. Vacuum leaks. Incorrect fuel pressure. Lean fuel injectors. An inaccurate MAF sensor. Repair as necessary. If problem was found and corrected, go to step 10. If problem was not found, go to step 7.
6. Check Purple/White wire between HO2S and PCM for short to ground or short to low signal circuit. If problem was found, repair as necessary. After repairs, go to step 10. If problem was not found, go to step 9.
7. Check HO2S connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 10. If problem was not found, go to next step.
8. Replace HO2S. See OXYGEN SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. If problem was found, repair as necessary. After repairs, go to step 10. If problem was not found, go to next step.
9. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
10. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
11. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

1. Exhaust system Inspect exhaust system for the following conditions: Leaks. Corrosion between 3-way catalytic converter and flange. Loose or missing hardware.
2. Poor Electrical Connection Or A Damaged Harness Inspect harness for a short to ground in HO2S2 high signal circuit. Ensure HO2S2 pigtail is not contacting exhaust. Check for the following conditions: Wiring contacting exhaust system. Improper mating. Broken locks. Improperly formed harness connectors. Damaged terminals. Poor terminal-to-wire connection. Damaged harness.
3. Intermittent Test Observe HO2S2 on scan tool while moving any related electrical connectors and wiring harness with ignition on. If malfunction is induced, HO2S2 display will change. This should help isolate location of malfunction.

Obstruction of air reference and degrade HO2S2 performance could result in any attempt to repair HO2S harness or connector.

HO2S2 must have a clean air reference in order for HO2S2 to function properly. This clean air reference is obtained by way of HO2S2 wires.

Scheme 10

DTC P0138: HO2S2 CIRCUIT - VOLTAGE HIGH

Note. For circuit reference, see WIRING DIAGRAMS article.

In order to control emissions, a catalytic converter converts any harmful exhaust emissions into harmless water vapor and carbon dioxide.

PCM has capability to monitor this process by using a rear heated oxygen sensor (HO2S2). HO2S2 , located in exhaust stream past catalytic converter, produces an output signal which indicates storage capacity of catalyst. This in turn indicates catalyst's ability to convert exhaust emissions effectively. If catalyst is functioning properly, HO2S2 signal will be far less active than signal produced by front oxygen sensor (O2S1).

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set.
2. Engine Coolant Temperature (ECT) is more than 158°F (70°C).
3. Battery voltage is more than 10 volts.
4. Fuel level is more than 10 percent.
5. Engine run time is more than 10 seconds.
6. Engine is operating in closed loop.
7. Throttle Position (TP) angle is between 8-50 percent for 4 seconds.
8. Manifold Absolute Pressure (MAP) is more than 25 kPa.

DTC sets when HO2S2 voltage is more than 1042 millivolts for 50-75 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Run engine until normal operating temperature is reached. Using scan tool, monitor HO2S voltage for sensor that applies to this DTC. If HO2S voltage is fixed at more than 994 millivolts, go to step 4. If HO2S voltage is not fixed at more than 994 millivolts, go to next step.
3. DTC is intermittent. If any additional DTCs are stored, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions). If no additional DTCs are stored, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Disconnect HO2S sensor. HO2S2 is located in exhaust stream past catalytic converter. Connect jumper wire between HO2S connector terminal "A" (Tan/White wire) and ground. Turn ignition on, engine off. Using DVOM connected to ground, measure voltage on HO2S connector terminal "B" (Purple/White wire) on PCM side. If voltage is 351-551 millivolts, go to next step. If voltage is not 351-551 volts, go to step 6.
5. HO2S is detecting a rich exhaust condition or may be contaminated. Check for one of the following conditions: HO2S connector water intrusion. silicone-contaminated HO2S. Fuel-contaminated engine oil. Incorrect fuel pressure. Leaking fuel pressure regulator. Rich fuel injectors. Repair as necessary. If problem was found and corrected, go to step 11. If problem was not found, go to step 8.
6. Turn ignition off. Remove jumper wire from HO2S connector terminal "A". Disconnect PCM connector C2. Turn ignition on, engine off. Using DVOM, measure voltage between PCM connector C2 terminal No. 24 (Purple/White wire) and ground. (Scheme 5) If voltage is more than 20 millivolts, go to next step. If voltage is not more than 20 millivolts, go to step 10.
7. Repair short to voltage in Purple/White wire between HO2S and PCM. After repairs, go to step 11.
8. Check HO2S connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 11. If problem was not found, go to next step.
9. Before replacing a contaminated HO2S, determine and repair cause of contamination. Replace HO2S. See OXYGEN SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 11.
10. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
11. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
12. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

Check for the following conditions

1. Rich Exhaust An overly rich exhaust may load catalyst causing high HO2S2 signal voltages.
2. Silicone Contamination Silicone contamination of HO2S2 could cause a false rich condition. A powdery White deposit on sensor will indicate this condition.
3. Malfunctioning HO2S2 If there is an internal short in HO2S2, HO2S2 voltage displayed on a scan tool will be more than 1000 millivolts. Disconnect HO2S2, and connect a jumper wire between HO2S2 low signal circuit to engine ground. Replace HO2S2 if displayed voltage goes from more than 1000 millivolts to approximately 450 millivolts.
4. Intermittent Test Observe HO2S2 on scan tool while moving related electrical connectors and wiring harness with ignition on. If malfunction is induced, HO2S2 display will change. This should help isolate location of malfunction.
5. Damaged Harness Inspect PCM harness for a short to voltage in HO2S2 high signal circuit.

Obstruction of air reference and degraded HO2S2 performance could result in any attempt to repair HO2S harness or connector.

HO2S2 must have a clean air reference in order for HO2S2 to function properly. This clean air reference is obtained by way of HO2S2 wires.

DTC P0140: HO2S2 CIRCUIT - INSUFFICIENT ACTIVITY

Note. For circuit reference, see WIRING DIAGRAMS article.

In order to control emissions, a catalytic converter converts any harmful exhaust emissions into harmless water vapor and carbon dioxide.

PCM has capability to monitor this process by using a rear heated oxygen sensor (HO2S2). HO2S2, located in exhaust stream past catalytic converter, produces an output signal which indicates storage capacity of catalyst. This in turn indicates catalyst's ability to convert exhaust emissions effectively. If catalyst is functioning properly, HO2S2 signal will be far less active than signal produced by front oxygen sensor (O2S1).

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set.
2. Battery voltage is more than 10 volts.
3. Fuel level is more than 10 percent.
4. Engine run time is more than 10 seconds.
5. Airflow is more than 5.5 grams per second (2.2L) or 140 grams per second (2.4L).
6. Engine Coolant Temperature (ECT) is more than 104°F (40°C).
7. Throttle Position (TP) is 8-56 percent.
8. Manifold Absolute Pressure (MAP) is more than 25 kPa.
9. Engine is operating in closed loop.

DTC sets when HO2S2 remains within 425-460 millivolts for 125 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. If any other DTCs are set (except HO2S DTCs), refer to other DTCs before proceeding with this procedure. Ensure engine is at operating temperature. Operate engine at speeds more than 1200 RPM for 2 minutes. Using scan tool, observe HO2S voltage parameter. If scan tool indicates HO2S voltage varying outside 400-500 millivolts, go to next step. If scan tool does not indicate HO2S voltage varying outside 400-500 millivolts, go to step 4.
3. Operate vehicle within failure records conditions. If scan tool indicates this DTC failed this ignition cycle, go to next step. If scan tool did not indicate this DTC failed this ignition cycle, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Inspect and test for exhaust leak, HO2S is installed correctly and damaged wiring. If problem was found, repair as necessary. After repairs, go to step 13. If problem was not found, go to next step.
5. Turn ignition off. Disconnect HO2S sensor. HO2S2 is located in exhaust stream past catalytic converter. Connect jumper wire between HO2S connector terminal "A" (Tan/White wire) and ground. (Scheme 10) Turn ignition on, engine off. Using DVOM connected to ground, measure voltage on HO2S connector terminal "B" (Purple/White wire) on PCM side. If voltage is 351-551 millivolts, go to next step. If voltage is not 351-551 volts, go to step 8.
6. Connect jumper wire between HO2S connector terminals (PCM side). Using scan tool, observe O2 VOLTAGE parameter. If scan tool indicates O2 voltage at or near zero millivolts, go to step 9. If scan tool does not indicate O2 voltage at or near zero millivolts, go to next step.
7. Check Tan/White wire between HO2S and PCM for open, high resistance or short to voltage. If problem was found, repair as necessary. After repairs, go to step 13. If problem was not found, go to step 11.
8. Check Purple/White wire between HO2S and PCM for open, high resistance or short to voltage. If problem was found, repair as necessary. After repairs, go to step 13. If problem was not found, go to step 11.
9. Check HO2S connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 13. If problem was not found, go to next step.
10. HO2S sensor has been contaminated. Contamination source must be removed prior to operating engine with replacement sensor. Possible sources of contamination include use of an incorrect silicone RTV sealant, engine coolant leakage into combustion chamber, excessive engine oil consumption, use of silicone-contaminated fuel and use of fuel containing lead. Replace HO2S sensor. See OXYGEN SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 13.
11. Check PCM connectors for poor connections. at the PCM. If problem was found, repair as necessary. After repairs, go to step 13. If problem was not found, go to next step.
12. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
13. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
14. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

Check oxygen sensor pigtail wire for breaks and contamination. An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation. Check for intermittent open in HO2S2 signal circuit wire. DO NOT attempt to repair damaged oxygen sensor connector or wiring. If damage is detected, replace oxygen sensor.

Obstruction of air reference and degraded HO2S2 performance could result in any attempt to repair HO2S harness or connector.

HO2S2 must have a clean air reference in order for HO2S2 to function properly. This clean air reference is obtained by way of HO2S2 wires.

DTC P0141: HO2S2 HEATER CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

In order to control emissions, a catalytic converter converts any harmful exhaust emissions into harmless water vapor and carbon dioxide.

PCM has capability to monitor this process by using a rear heated oxygen sensor (HO2S2). HO2S2, located in exhaust stream past catalytic converter, produces an output signal which indicates storage capacity of catalyst. This in turn indicates catalyst's ability to convert exhaust emissions effectively. If catalyst is functioning properly, HO2S2 signal will be far less active than signal produced by front oxygen sensor (O2S1).

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set.
2. Ignition 1 signal is more than 10 volts.
3. Engine Coolant Temperature (ECT) less than 113°F (45°C).
4. Intake Air Temperature (IAT) less than 113°F (45°C).
5. Difference between ECT and IAT is less than 45°F (7°C).
6. Fuel level is more than 10 percent.
7. Rear HO2S voltage is between 395-495 millivolts.

DTC sets when HO2S voltage does not go more than 600 millivolts or less than 300 millivolts 110-255 seconds after a cold start.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. HO2S must be cool before proceeding with diagnosis. Ignition must remain off for at least one-half hour before proceeding with diagnosis. Connect scan tool. Set up scan tool with proper vehicle identification information prior to turning ignition on. Turn ignition on, engine off. As quickly as possible, observe and record HO2S voltage for sensor that applies to this DTC. Monitor HO2S voltage for 2 minutes. If HO2S voltage increases or decreases from initial voltage by at least 150 millivolts, go to next step. If HO2S voltage does not increase or decrease from initial voltage by at least 150 millivolts, go to step 4.
3. Condition that set this DTC is not present. This DTC may have been set by one of the following conditions: Intermittently open or high resistance HO2S high signal circuit, or low signal circuit. Intermittently open or high resistance HO2S heater ignition 1 voltage, or heater ground circuit. Faulty HO2S or PCM connector terminal contact. Defective HO2S. Repair as necessary. If problem was found and corrected, go to step 15. If problem was not found, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Disconnect HO2S connector. HO2S2 is located in exhaust stream past catalytic converter. Connect test light between HO2S connector terminals "C" (Black wire) and "D" (Brown wire) at engine harness side. (Scheme 10) Turn ignition on, engine off. If test light is on, go to next step. If test light is off, go to step 6.
5. Disconnect test light. Connect jumper wire between HO2S connector terminal "A" (Tan/White wire) and ground. Connect jumper wire between HO2S connector terminal "B" (Purple/White wire) and ground. Using scan tool, monitor HO2S voltage for sensor that applies to this DTC. Ensure ignition is on while engine is off. If HO2S voltage is less than 20 millivolts, go to step 8. If HO2S voltage is not less than 20 millivolts, go to step 7.
6. Connect test light between HO2S connector terminal (Brown wire) at engine harness side and ground. Ensure ignition is on while engine is off. If test light is on, go to step 10. If test light is off, go to step 11.
7. Turn ignition off. Remove jumpers. Using DVOM, measure resistance of Purple/White wire between HO2S and PCM and then Tan/White wire between PCM and HO2S. If resistance is less than 5 ohms, go to step 13. If resistance is not less than 5 ohms, go to step 12.
8. Check HO2S connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 15. If problem was not found, go to next step.
9. Replace HO2S. See OXYGEN SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 15.
10. Repair open in Black wire between HO2S and ground. After repairs, go to step 15.
11. Repair lack of voltage on Brown wire between HO2S and underhood fuse block. Blown fuse or lack of voltage to fuse may cause other DTCs or symptoms to be present. After repairs, go to step 15.
12. Repair circuit that measured high resistance. After repairs, go to step 15.
13. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 15. If problem was not found, go to next step.
14. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
15. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
16. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

Check oxygen sensor pigtail wire for breaks and contamination. An intermittent problem can be caused by misrouted harness, rubbed through wire insulation or broken wire inside insulation. DO NOT attempt to repair damaged oxygen sensor connector or wiring. If damage is detected, replace oxygen sensor.

Obstruction of air reference and degraded HO2S2 performance could result in any attempt to repair HO2S harness or connector.

HO2S2 must have a clean air reference in order for HO2S2 to function properly. This clean air reference is obtained by way of HO2S2 wires.

PCM controls air/fuel metering system in order to provide best possible combination of driveability, fuel economy and emission control. Fuel delivery is controlled differently during open and closed loop. During open loop, PCM determines fuel delivery based on sensor signals, without oxygen sensor input. During closed loop, PCM adds oxygen sensor inputs to calculate short and long term fuel trim (fuel delivery adjustments). Short term fuel trim values change rapidly in response to HO2S voltage signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel (A/F) ratio of 14.7:1. Fuel Trim (FT) index is average of short and long term fuel trim and purge learn memory based on engine speed and load. If PCM detects an excessively lean condition, this DTC will set.

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0125 , P0131, P0132, P0133, P0134, P0201-P0204, P0300, P0301-P0304, P0325, P0341, P0446, P0502, P0503, P0506, P0507, P0601, P0602, P1133, or P1441 are not set.
2. Engine Coolant Temperature (ECT) is 14-239°F (60-115°C).
3. Intake air temperature is -13 to 239°F (-25 to 115°C).
4. Manifold Absolute Pressure (MAP) is more than 26 kPa.
5. Vehicle speed is less than 82 MPH.
6. Engine speed is 55-3400 RPM.
7. Barometric (BARO) pressure is more than 72 kPa.
8. Fuel ethanol composition is less than 88 percent.
9. Fuel level is more than 9.8 percent.

DTC sets when fuel trim index is more than 23 percent.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Start engine and drive vehicle under normal conditions until engine reaches operating temperature and is in closed loop. Turn engine off. Turn ignition on, engine off. Review FREEZE FRAME RECORDS and/or FAILURE RECORDS and record displayed data for this DTC. If scan tool indicates fuel trim index is more than 23 percent, go to next step. If scan tool does not indicate fuel trim index is more than 23 percent, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
3. Operate engine at idle. Using scan tool, observe O2S parameters. If scan tool indicates values are within 200-800 millivolts and fluctuating, go to next step. If scan tool does not indicate values are within 200-800 millivolts and fluctuating, go to step 5 .
4. Turn engine off. Visually and physically inspect the following items: Vacuum hoses for splits, kinks, and proper connections. Fuel pressure is too low. This may cause this DTC to set. Fuel contamination. Check for alcohol or contaminants in fuel. If problem was found, repair as necessary. After repairs, go to step 7 . If problem was not found, go to step 6 .
5. Turn engine off. Check O2S for proper installation. Check to ensure electrical connectors and wires are secured and not contacting exhaust system. Check Purple wire and Tan wire between O2S and PCM for short. If problem was found, repair as necessary. After repairs, go to step 7 . If problem was not found, diagnose fuel system. See appropriate BASIC DIAGNOSTIC PROCEDURES article.
6. Operate engine at idle. Check for missing, loose, or leaking exhaust components. Check for vacuum leaks at intake manifold, throttle body and injector "O" rings. Check air induction system and air intake ducts for leaks. Check crankcase ventilation system for leaks. If problem was found, repair as necessary. After repairs, go to next step. If problem was not found, diagnose engine mechanical problem. See appropriate article in ENGINES.
7. After repairs, using scan tool Fuel Trim Reset function, reset LONG TERM FUEL TRIM. Clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
8. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

System will go lean if an injector is not suppling enough fuel. A lean condition could be present during high fuel demand due to a fuel pump that does not pump enough fuel.

An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation. DO NOT attempt to repair damaged oxygen sensor connector or wiring. If damage is detected, replace oxygen sensor.

Exhaust Oxygen Sensor (O2S) is used to determine oxygen content of exhaust. Oxygen content indicates when engine is operating lean or rich. When engine is operating lean, exhaust will have more oxygen content. Once at operating temperature, O2S will produce a voltage in relation to oxygen content of exhaust. O2S requires an operating temperature of 600°F (360°C) to produce voltage. O2S will produce more voltage when exhaust is rich and less voltage when exhaust is lean. O2S operating voltage range is 0.10-1 volt (100-1000 mV).

Alternate Fuel Engine Control Module (AF ECU) uses closed loop air/fuel metering system when O2S is at operating temperature. During normal closed loop fuel control operation, AF ECU will add fuel (enriches mixture) when O2S indicates lean exhaust content. When O2S indicates rich exhaust content, AF ECU will subtract fuel (lean out mixture). This addition and subtraction to air/fuel mixture may be indicated on scan tool as long and short term fuel trim values. Short term values are adjustments to fuel mixture that occur quickly. Long term values are adjustments to fuel mixture that accumulate over longer periods of time. Long and short term fuel trim values are displayed on scan tool as percent. Positive percentage values indicate fuel is being added and negative percentage values indicate fuel is being subtracted from the mixture.

For DTC to run, the following conditions must be met

1. Engine is operating on alternative fuel.
2. Engine coolant temperature is more than 102°F (49°C).
3. AF ECU is operating in closed loop fuel control.

DTC will set when AF ECU monitors short term fuel trim at +50 percent for at least 5 continuous seconds or AF ECU monitors long term fuel trim at +45 percent for at least 5 continuous seconds.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Using scan tool, capture DTC information from AF ECU. Check for poor connections at PCM and AF ECU. PCM is located inside right front fender. AF ECU is located behind left front fascia, below headlight. Check for DTCs. If additional DTCs are set, go to next step. If no additional DTCs are set, go to step 4.
3. Diagnose and repair additional DTCs before attempting to diagnose this DTC. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions). After repairing additional DTCs, go to step 12.
4. DTC may have been set by one of the following conditions: An O2S signal wire intermittently open or shorted to ground. O2S connector water intrusion. Lean engine condition such as incorrect CNG fuel pressure, vacuum leaks, PCV system malfunction or exhaust system leaks between engine and oxygen sensor. Repair as necessary. After repairs, go to step 12. If condition is not found and repaired, go to next step.
5. Reconnect all disconnected or removed components. Using scan tool, clear DTCs from PCM and AF ECU. Communicate with AF ECU and reset fuel trim values. Turn ignition off for 30 seconds. Start engine and view captured data FREEZE FRAME records on scan tool. Operate vehicle within conditions to run DTC. See «CODE ENABLE CRITERIA»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l). Monitor short term fuel trim values. If fuel trim values indicate a lean mixture condition is present, go to step 7. If fuel trim values do not indicate a lean mixture condition is present, go to next step.
6. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
7. Perform fuel system diagnosis then return to this test step. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS (2.2L - CAVALIER CNG) in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article. If fuel system problem is found and repaired, go to step 12. If fuel system problem is not found and repaired, go to next step.
8. Turn engine off. Disconnect O2S, PCM and AF ECU connectors. PCM is located inside right front fender. AF ECU is located behind left front fascia, below headlight. Using DVOM, check for continuity in Purple wire between O2S connector terminal "B" and AF ECU White/Clear connector C002 terminal No. 4 and Tan wire between O2S connector terminal "A" and AF ECU White/Clear connector C002 terminal No. 5. (Scheme 3) Repair as necessary. After repairs, go to step 12. If circuits are okay, go to next step.
9. Reconnect all disconnected or removed components. Using scan tool, clear DTCs from PCM and AF ECU. Communicate with PCM and reset fuel trim values. Turn ignition off. Remove CNG fuse (20-amp) located in underhood fuse block. (Scheme 11) Removing CNG fuse will force switch to gasoline operation and Fuel Indicator Light (FIL) will not illuminate. Start engine and view captured data FREEZE FRAME records on scan tool. Operate vehicle within conditions to run DTC. See «CODE ENABLE CRITERIA»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l). Monitor short term fuel trim values. If fuel trim values indicate a lean mixture condition is present and/or fuel trim DTC resets, go to next step. If fuel trim values do not indicate a lean mixture condition is present and fuel trim DTC does not reset, go to step 11.
10. Repair cause for lean condition as outlined in step 4. After repairs, go to step 12.
11. Replace Gas Mass Sensor/Mixture Control Valve (GMS/MCV). (Scheme 12) After repairs, go to next step.
12. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may also be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Scheme 11

Scheme 12

DTC P0172: FUEL TRIM SYSTEM RICH (GASOLINE)

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM controls air/fuel metering system in order to provide best possible combination of driveability, fuel economy and emission control. Fuel delivery is controlled during open and closed loop. During open loop, PCM determines fuel delivery based on sensor signals, without oxygen sensor input. During closed loop, oxygen sensor inputs are added and used by PCM to calculate short and long term fuel trim (fuel delivery adjustments). Short term fuel trim values change rapidly in response to heated oxygen sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustments in order to maintain air/fuel ratio of 14.7:1. Fuel trim index is average of short and long term fuel trim and purge learn memory based on engine speed and load. Fuel trim diagnostic will conduct a test to determine if a rich failure actually exists or if excessive vapor from Evaporative Emission (EVAP) canister is causing a rich condition. If PCM detects an excessively rich condition, this diagnostic trouble code (DTC) will set. If PCM detects excessive vapor then a pass is logged.

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0125 , P0131, P0132, P0133, P0134, P0201-P0204, P0300, P0301-P0304, P0325, P0341, P0446, P0502, P0503, P0506, P0507, P0601, P0602, P1133, or P1441 are not set.
2. Engine Coolant Temperature (ECT) is 140-239°F (60-115°C).
3. Intake air temperature is -13 to 239°F (-25 to 115°C).
4. Manifold Absolute Pressure (MAP) is more than 26 kPa.
5. Vehicle speed is less than 82 MPH.
6. Engine speed is 550-3400 RPM.
7. Barometric pressure is more than 72 kPa.
8. Fuel ethanol composition is less than 88 percent.
9. Fuel level is more than 9.8 percent.

DTC sets when fuel trim index is less than -42 percent. Diagnostics have determined that a rich condition was not due to excessive vapor.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Start engine and drive vehicle under normal conditions until engine reaches operating temperature and is in closed loop. Turn engine off. Turn ignition on, engine off. Review FREEZE FRAME RECORDS and/or FAILURE RECORDS and record displayed data for this DTC. If scan tool indicates fuel trim index is less than -42 percent, go to next step. If scan tool does not indicate fuel trim index is less than -42 percent, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
3. Operate engine at idle. Using scan tool, observe O2S parameters. If scan tool indicates values are within 200-800 millivolts and fluctuating, go to next step. If scan tool does not indicate values are within 200-800 millivolts and fluctuating, go to step 5 .
4. Turn engine off. Inspect the following items: Vacuum hoses for splits, kinks, and proper connections. Air intake duct for being collapsed or restricted. Air filter for dirt or for restrictions. Objects blocking throttle body. If problem was found, repair as necessary. After repairs, go to step 7 . If problem was not found, go to step 6 .
5. Turn engine off. Check O2S for proper installation. Check to ensure electrical connectors and wires are secured and not contacting exhaust system. If problem was found, repair as necessary. After repairs, go to step 7 . If problem was not found, diagnose fuel system. See appropriate BASIC DIAGNOSTIC PROCEDURES article.
6. Inspect for the following: Check for excessive fuel in crankcase. Inspect evaporative emissions control system. Test fuel pressure regulator for proper operation. Check to ensure all injectors are functioning properly. Perform fuel injector balance test. If problem was found, repair as necessary. After repairs, go to next step. If problem was not found, diagnose engine mechanical problem. See appropriate article in ENGINES.
7. After repairs, using scan tool Fuel Trim Reset function, reset LONG TERM FUEL TRIM. Clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
8. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

Fuel contamination, such as water and alcohol, will affect fuel trim. System will go rich if injectors are suppling to much fuel. An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation. DO NOT attempt to repair damaged oxygen sensor connector or wiring. If damage is detected, replace oxygen sensor.

Exhaust Oxygen Sensor (O2S) is used to determine oxygen content of exhaust. Oxygen content indicates when engine is operating lean or rich. When engine is operating lean, exhaust will have more oxygen content. Once at operating temperature, O2S will produce a voltage in relation to oxygen content of exhaust. O2S requires an operating temperature of 600°F (360°C) to produce voltage. O2S will produce more voltage when exhaust is rich and less voltage when exhaust is lean. O2S operating voltage range is 0.10-1.00 volt (100-1000 mV).

Alternate Fuel Engine Control Module (AF ECU) uses closed loop air/fuel metering system when O2S is at operating temperature. During normal closed loop fuel control operation, AF ECU will add fuel (enriches mixture) when O2S indicates lean exhaust content. When O2S indicates rich exhaust content, AF ECU will subtract fuel (lean out mixture). This addition and subtraction to air/fuel mixture may be indicated on scan tool as long and short term fuel trim values. Short term values are adjustments to fuel mixture that occur quickly. Long term values are adjustments to fuel mixture that accumulate over longer periods of time. Long and short term fuel trim values are displayed on scan tool as percent. Positive percentage values indicate fuel is being added and negative percentage values indicate fuel is being subtracted from the mixture.

For DTC to run, the following conditions must be met

1. Engine is operating on alternative fuel.
2. Engine coolant temperature is more than 120°F (49°C).
3. AF ECU is operating in closed loop fuel control.

DTC will set when AF ECU monitors short term fuel trim at -50 percent for at least 5 continuous seconds or AF ECU monitors long term fuel trim at -45 percent for at least 5 continuous seconds.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Using scan tool, capture DTC information from AF ECU. Check for poor connections at PCM and AF ECU. PCM is located inside right front fender. AF ECU is located behind left front fascia, below headlight. Check for DTCs. If additional DTCs are set, go to next step. If no additional DTCs are set, go to step 4.
3. Diagnose and repair additional DTCs before attempting to diagnose this DTC. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions). After repairing additional DTCs, go to step 14.
4. DTC may have been set by one of the following conditions: An O2S signal wire intermittently shorted to voltage. RTV silicone contaminated O2S. Rich engine condition such as EVAP canister purge system malfunction, gasoline contaminated engine oil, incorrect CNG fuel pressure, leaking gasoline fuel pressure regulator or a restricted air filter or intake air duct. Repair as necessary. After repairs, go to step 14. If condition is not found and repaired, go to next step.
5. Reconnect all disconnected or removed components. Using scan tool, clear DTCs from PCM and AF ECU. Communicate with AF ECU and reset fuel trim values. Turn ignition off for 30 seconds. Start engine and view captured data FREEZE FRAME records on scan tool. Operate vehicle within conditions to run DTC. See «CODE ENABLE CRITERIA»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l). Monitor short term fuel trim values. If fuel trim values indicate a rich mixture condition is present, go to step 7. If fuel trim values do not indicate a rich mixture condition is present, go to next step.
6. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
7. Perform fuel system diagnosis then return to this test step. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS (2.2L - CAVALIER CNG) in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article. If fuel system problem is found and repaired, go to step 14. If fuel system problem is not found and repaired, go to next step.
8. Turn engine off. Disconnect O2S, PCM and AF ECU connectors. PCM is located inside right front fender. AF ECU is located behind left front fascia, below headlight. Using DVOM, check for continuity in Purple wire between O2S connector terminal "B" and AF ECU White/Clear connector C002 terminal No. 4 and Tan wire between O2S connector terminal "A" and AF ECU White/Clear connector C002 terminal No. 5. (Scheme 3) Check for short to ground or short to other circuits in Purple or Tan wires. Check for poor connections at PCM, AF ECU and O2S. Repair as necessary. After repairs, go to step 14. If circuits and connections are okay, go to next step.
9. Reconnect all disconnected or removed components. Using scan tool, clear DTCs from PCM and AF ECU. Communicate with PCM and reset fuel trim values. Turn ignition off. Remove CNG fuse (20-amp) located in underhood fuse block. (Scheme 11) Removing CNG fuse will force switch to gasoline operation and Fuel Indicator Light (FIL) will not illuminate. Start engine and view captured data FREEZE FRAME records on scan tool. Operate vehicle within conditions to run DTC. See «CODE ENABLE CRITERIA»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l). Monitor short term fuel trim values. If fuel trim values indicate a rich mixture condition is present and/or fuel trim DTC resets, go to next step. If fuel trim values do not indicate a rich mixture condition is present and fuel trim DTC does not reset, go to step 13.
10. Remove O2S and visually inspect for RTV silicone contamination. If O2S is contaminated, go to step 12. If O2S is not contaminated, go to next step.
11. Repair cause of engine running rich condition as outlined in step 4. After repairs, go to step 14.
12. Replace O2S. Before replacing O2S, repair source of contamination. After repairs, go to step 14.
13. Replace Gas Mass Sensor/Mixture Control Valve (GMS/MCV). (Scheme 12) After repairs, go to next step.
14. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may also be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

DTC P0201-P0204: INJECTOR CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

Note. Last number of DTC refers to injector number that set DTC.

PCM enables appropriate fuel injector on intake stroke for each cylinder. An ignition voltage is supplied to fuel injectors. PCM controls each fuel injector by grounding control circuit via a solid state device called a driver. PCM monitors status of each driver. If PCM detects an incorrect voltage for commanded state of driver, a fuel injector control DTC sets.

1. Engine is running.
2. Ignition voltage is 9-18 volts.

DTC sets when PCM detects an incorrect voltage on fuel injector control circuit for 30 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, record FREEZE FRAME and/or FAILURE RECORDS data for this DTC, then clear DTCs. Idle engine at normal operating temperature. Using scan tool, observe misfire current counters. If any misfire current counters are incrementing, go to step 4 . If no misfire current counters are incrementing, go to next step.
3. Observe FREEZE FRAME and/or FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or as close to FREEZE FRAME and/or FAILURE RECORDS data that you observed. If DTC fails this ignition cycle, go to next step. If DTC does not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
4. Turn ignition off. Disconnect appropriate harness connector of fuel injector. Turn ignition on, engine off. Using test light connected to ground, probe injector connector terminal "A" (Gray wire). Command fuel pump ON with scan tool. If test light is on when fuel pump is commanded ON, go to next step. If test light is off when fuel pump is commanded ON, go to step 11 .
5. Connect Fuel Injector Test Light (J 34730-405) between terminals of fuel injector harness connector. Start engine. If test light blinks, go to step 9 . If test light does not blink, go to next step.
6. If test light remains on at all times, go to step 8 . If test light does not remain on at all times, go to next step.
7. Check control circuit of fuel injector for short to voltage or open. See «INJECTOR CONTROL CIRCUIT WIRE COLOR»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) table for wire color. If problem was found, repair as necessary. After repairs, go to step 14 . If problem was not found, go to step 10 .
8. Check control circuit of fuel injector for short to ground. See «INJECTOR CONTROL CIRCUIT WIRE COLOR»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) table for wire color. If problem was found, repair as necessary. After repairs, go to step 14 . If problem was not found, go to step 13 .
9. Check fuel injector connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 14 . If problem was not found, go to step 12 .
10. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 14 . If problem was not found, go to step 13 .
11. Repair open or short to ground in Gray wire between fuel injector and underhood fuse block. After repairs, go to step 14 .
12. Replace fuel injector. See FUEL RAIL & INJECTORS in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 14 .
13. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
14. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
15. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

INJECTOR CONTROL CIRCUIT WIRE COLOR

Performing fuel injector coil test may help isolate an intermittent condition. See FUEL INJECTOR COIL TEST in appropriate SYSTEM & COMPONENT TESTING article.

Transmission fluid pump is constantly circulating fluid through torque converter. Hot fluid leaving converter flows through transmission cooler lines to oil cooler, located in vehicle radiator. From cooler, fluid returns to transmission.

Lube 1 fluid flows through input shaft to lubricate transmission components in front of transmission. Lube 2 fluid circuit is fed by line pressure at pressure regulator valve. Lube 2 fluid flows through oil feed pipes, and into forward clutch support. Lube 2 fluid provides lubrication to rear components of transmission.

When PCM detects a high transmission fluid temperature for a long period of time, then DTC P0218 sets.

1. DTCs P0711, P0712 or P0713 are not set.

DTC sets when transmission fluid temperature is more than 260°F (130°C) for 10 minutes.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Record DTC FAILURE RECORDS. Clear DTC. If fluid level was checked, go to next step. If fluid level was not checked, see appropriate AUTOMATIC TRANSMISSION SERVICING article in TRANSMISSION SERVICING.
3. Inspect transmission cooling system for the following conditions: Airflow restrictions. Airflow blockage. Debris. Damaged cooler lines. If problem was found, repair as necessary. After repairs, go to step 7 . If problem was not found, go to next step.
4. Inspect valve body for the following conditions: Stuck pressure regulator valve. Leaking pressure regulator valve. If problem was found, repair as necessary. After repairs, go to step 7 . If problem was not found, go to next step.
5. Inspect oil feed tubes for the following conditions: Restrictions. Leaking seals. If problem was found, repair as necessary. After repairs, go to step 7 . If problem was not found, go to next step.
6. Inspect torque converter for stator damage. See PERFORMANCE TESTS in appropriate HYDRA-MATIC OVERHAUL article. After repairs, go to next step.
7. Perform the following procedure in order to verify repair: Select DTC. Select CLEAR INFO. Start and idle engine until it reaches normal operating temperature. Select ENGINE RUN TIME and TRANS. FLUID TEMP. on scan tool. Drive vehicle for 15 minutes. Ensure transmission fluid temperature has stabilized and is less than 264°F (129°C). Select Specific DTC. Enter DTC P0218. If DTC does not reset, system is okay.

Ask customer about overloading vehicle, exceeding trailer-towing limit, or towing in Overdrive.

DTC P0300: ENGINE MISFIRE DETECTED (2.2L)

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM uses information from Ignition Control Module (ICM) and Camshaft Position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring variations in crankshaft rotation speed for each cylinder, PCM is able to detect individual misfire events. A misfire rate that is high enough can cause 3-way catalytic (TWC) converter to overheat under certain conditions. Malfunction Indicator Lamp (MIL) will flash on and off when conditions for TWC converter overheating are present.

1. DTCs P0105, P0107, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0128, P0130, P0131, P0132, P0133, P0134, P0137, P0138, P0140, P0171, P0172, P0325, P0336, P0502, P0503, P0506, P0507, P0601, P0602, P1133, P1137, P1138, P1171, P1336, or P1621 are not set.
2. Engine speed is 469-5900 RPM.
3. Battery voltage is 9-17 volts.
4. Engine Coolant Temperature (ECT) is 20-254°F (-7 to 123°C).
5. Engine has been running more than 5 seconds.
6. Throttle Position (TP) has not increased more than 8 percent in one second.
7. TP has not decreased more than 1.5 percent in one second.

DTC sets when PCM is detecting a crankshaft rotation speed variation indicating a misfire rate sufficient to cause emissions levels to exceed mandated standard.

Note. Before clearing DTCs, record FREEZE FRAME/FAILURE RECORDS for reference with a scan tool. This data will be lost when you use CLEAR DTC information function.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. If there are any other DTCs stored, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If there are no other DTCs stored, go to next step.
3. Start engine. Monitor MISFIRE CURRENT parameter in MISFIRE data list with a load on engine. Refer to FREEZE FRAME data. If MISFIRE COUNTER is increasing, go to step 5 . If MISFIRE COUNTER is not increasing, go to next step.
4. Turn engine off. Use a spray bottle filled with water to wet down secondary ignition system. Start engine. Monitor MISFIRE CURRENT parameter in MISFIRE data list with a load on engine. If scan tool indicates a misfire is present, go to next step. If scan tool does not indicate a misfire is present, go to step 17 .
5. If misfire is random on all cylinders, go to step 9 . If misfire is consistent on specific cylinders, go to next step.
6. Turn ignition off. Connect spark tester to spark plug wires of cylinders indicating a misfire. Start and idle engine. If tester indicates spark is consistent on all tested spark plug wires, go to next step. If tester does not indicate spark is consistent on all tested spark plug wires, go to step 8 .
7. Remove spark plugs from cylinders that indicate a misfire. Inspect spark plugs. If problem was found, go to step 16 . If problem was not found, go to next step.
8. Install spark plugs in cylinders that were not indicating a misfire. Start engine. Monitor MISFIRE CURRENT parameter in MISFIRE data list. If misfires changed cylinders, go to step 14 . If misfires did not change cylinders, go to step 10 .
9. Perform fuel system diagnostic. See appropriate BASIC DIAGNOSTIC PROCEDURES article. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 15 .
10. Perform Fuel Injector Balance Test. See FUEL INJECTOR BALANCE TEST in appropriate SYSTEM & COMPONENT TESTING article. If problem was found, go to next step. If problem was not found, go to step 16 .
11. Connect Injector Test Light (J 34730-405) on injector harness connector, on PCM side. Crank engine. If injector test light flashes for each injector, go to step 13 . If injector test light does not flash for each injector, go to next step.
12. Using DVOM, check injector harness for short to voltage between PCM connector and injector connector that failed balance test. If voltage is more than one volt, go to next step. If voltage is not more than one volt, go to step 15 .
13. Repair short to voltage on injector control circuit. After repairs, go to step 18 .
14. Replace spark plugs. After repairs, go to step 18 .
15. Physically and visually check for these conditions in the following order: Contaminated fuel. Fouled or damaged spark plugs. Ignition coil and connections. Restricted exhaust system. PCM grounds. If problem was found, repair as necessary. After repairs, go to step 18 . If problem was not found, go to next step.
16. Check and repair engine mechanical problems. See appropriate article in ENGINES. After repairs, go to step 18 . If problem was not found, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
17. Perform Crankshaft Position (CKP) variation learn procedure. See «CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__crankshaft-position-sensor-system-variation-learn) under PROGRAMMING. After repairs, go to next step.
18. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
19. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

An intermittent DTC can also be the result of a defective reluctor wheel. Remove crankshaft sensor, and inspect reluctor wheel through crankshaft sensor mount hole. Inspect porosity and condition of reluctor wheel.

DTC P0300: ENGINE MISFIRE DETECTED (2.4L)

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM uses information from Ignition Control Module (ICM) and Camshaft Position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring variations in crankshaft rotation speed for each cylinder, PCM is able to detect individual misfire events. A misfire rate that is high enough can cause 3-way catalytic converter to overheat under certain conditions. Malfunction Indicator Lamp (MIL) will flash on and off when conditions for 3-way catalytic converter overheating are present.

1. DTCs P0105, P0107, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0171, P0172, P0325, P0336, P0340, P0341, P0342, P0502, P0503, P0506, P0507, P0601, P0740, P0742, P1133, or P1621 are not set.
2. Engine speed is 469-6400 RPM.
3. Battery voltage is 9-17 volts.
4. Engine Coolant Temperature (ECT) is 20-254°F (-7 to 123°C).
5. Engine has been running for more than 5 seconds.
6. Throttle Position (TP) has not increased more than 8 percent in one second.
7. TP has not decreased more than 1.5 percent in one second.

DTC sets when misfire total is more than 8 counts.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. If there are any other DTCs stored, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions). If there are no other DTCs stored, go to next step.
3. Turn ignition off. Perform a visual and physical inspection. If problem was found, repair as necessary. After repairs, go to step 27. If problem was not found, go to next step.
4. Start and idle engine. Using scan tool, observe MISFIRE CURRENT COUNTS. If any MISFIRE CURRENT COUNTS are incrementing, go to step 6. If no MISFIRE CURRENT COUNTS are incrementing, go to next step.
5. Operate vehicle within FREEZE FRAME data and code enable criteria. If any MISFIRE CURRENT COUNTS are incrementing, go to next step. If no MISFIRE CURRENT COUNTS are incrementing, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
6. If misfire is present in all cylinders, go to next step. If misfire is not present in all cylinders, go to step 11.
7. Perform fuel system diagnosis. See appropriate BASIC DIAGNOSTIC PROCEDURES article. If problem was found, repair as necessary. After repairs, go to step 27. If problem was not found, go to next step.
8. Turn ignition off. Check fuel for alcohol and contaminates. If problem was found, go to step 10. If problem was not found, go to next step.
9. Inspect for basic engine problems. See appropriate article in ENGINES. After repairs, go to step 27.
10. Perform fuel system cleaning. After repairs, go to step 27.
11. Turn ignition off. Remove fuel pump relay. Remove ICM assembly, keeping ICM assembly connected to harness connector. Connect fused jumper wire between ICM assembly and ground. Install Spark Plug Jumper Wire Kit (J 36012-A). Install Spark Tester (J 26792) on No. 1 spark plug jumper wire. Ground No. 4 spark plug jumper wire. No. 4 wire is companion to No. 1. Crank engine with remaining spark plug wires connected. Repeat step with spark tester installed on No. 4 wire and grounding No. 1. Perform test for No. 2 and No. 3 spark plugs. Make sure companion wire is grounded. If spark tester sparks on all cylinders, go to next step. If spark tester does not spark on all cylinders, go to step 13.
12. Turn ignition off. Inspect for malfunctioning spark plugs in cylinders that indicated a misfire. If problem was found, repair as necessary. After repairs, go to step 27. If problem was not found, go to step 9.
13. Disconnect PCM connector. Reconnect spark tester on spark plug jumper wire that did not spark. Ground companion spark plug jumper wire. Turn ignition on, engine off. Connect test light to battery voltage. Momentarily touch affected ICM timing control circuit at PCM connector C2 terminal No. 26 (White wire) for 1/4 coil or PCM connector C1 terminal No. 25 (Orange wire) for 2/3 coil. (Scheme 5) A spark should be present when test light is removed from circuit. If spark tester sparked, go to step 23. If spark tester did not spark, go to next step.
14. Turn ignition off. Remove spark plug jumper wires from affected cylinder and companion at coil housing. Connect DVOM between secondary ignition coil terminals. If resistance is 4-8 k/ohms, go to next step. If resistance is not 4-8 k/ohms, go to step 16.
15. Remove ignition coil housing from cover. Disconnect ignition coil harness connector at ICM. Connect 2 test lights to battery voltage. Probe affected ignition coil control terminal at ICM connector C2 terminal "C" (White wire) for 1/4 coil or terminal "B" (White wire) for 2/3 coil with one test light. Turn ignition on, engine off. DO NOT leave test light connected to PCM ICM circuit connector for more than 5 seconds at a time. Doing so may damage ignition coil and/or ICM. Momentarily touch affected ICM timing control circuit at PCM connector C2 terminal No. 26 (White wire) for 1/4 coil or PCM connector C1 terminal No. 25 (Orange wire) for 2/3 coil with one test light while monitoring other test light. If test light blinks, go to step 17. If test light does not blink, go to step 18.
16. Remove ignition coil housing. Disconnect ignition coil connector from ICM. Remove affected ignition coil from housing. Retest resistance between secondary terminals of coil. If resistance is 4-8 k/ohms, go to step 20. If resistance is not 4-8 k/ohms, go to step 21.
17. Turn ignition off. Test coil control circuit (White wire) between ICM and affected ignition coil for open, short to ground, short to voltage or poor connection at ignition coil or ICM. If problem was found, repair as necessary. After repairs, go to step 27. If problem was not found, go to step 19.
18. Turn ignition off. Disconnect ICM 11-pin connector. Test affected ICM timing control input circuit (White wire or Orange wire) between ICM and PCM for open, short to ground or short to voltage. If problem was found, repair as necessary. After repairs, go to step 27. If problem was not found, go to step 24.
19. Disconnect ignition coil connector from affected ignition coil. Reconnect ignition coil connector to ICM. Connect test light to ground. Turn ignition on, engine off. Probe coil connectors terminal "B" (Brown wire) one at a time with test light. If test light is on for both circuits, go to next step. If test light is not on for both circuits, go to step 22.
20. Inspect affected cylinder and companion for corrosion or damage to spark plug boot, ignition coil springs or ignition coil housing. If problem was found, repair as necessary. After repairs, go to step 27. If problem was not found, go to next step.
21. Check ignition coil and PCM connectors of affected coil for poor connections. If problem was found, repair as necessary. After repairs, go to step 27. If problem was not found, go to step 25.
22. Turn ignition off. Repair open in Brown wire between ignition coil and ICM as necessary. After repairs, go to step 27.
23. Turn ignition off. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 27. If problem was not found, go to step 26.
24. Replace ICM. See IGNITION CONTROL MODULE (IDI) in appropriate REMOVAL, OVERHAUL & INSTALLATION. After repairs, go to step 27.
25. Replace affected ignition coil. See IGNITION COIL (IDI) in appropriate REMOVAL, OVERHAUL & INSTALLATION. After repairs, go to step 27.
26. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
27. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
28. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

An intermittent can also be the result of a defective reluctor wheel. Remove crankshaft sensor and inspect reluctor wheel through sensor mount hole. Inspect for porosity and general condition of wheel.

Ensure Ignition Control Module (ICM) ground circuit has less than 0.5 ohm resistance.

DTC P0301-P0304: CYLINDER MISFIRE DETECTED (2.2L)

Note. For circuit reference, see WIRING DIAGRAMS article.

Note. Last number of DTC refers to cylinder number that set DTC.

PCM uses information from Ignition Control Module (ICM) and Camshaft Position (CMP) sensor in order to determine when an engine misfire occurs. By monitoring variations in crankshaft rotation speed for each cylinder, PCM is able to detect individual misfire events. A high misfire rate can cause the 3-way catalytic (TWC) converter to overheat under certain conditions. Malfunction Indicator Lamp (MIL) will flash on and off when conditions for TWC converter overheating are present.

1. Engine speed is 469-5906 RPM.
2. Battery voltage is 9-17 volts.
3. Engine Coolant Temperature (ECT) is 20-254°F (-7 to 123°C).
4. Engine has been running more than 5 seconds.
5. Fuel level is more than 10 percent.

DTC sets when PCM detects a crankshaft rotation speed variation indicating a misfire rate sufficient to cause emissions levels to exceed a mandated standard.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. If there are any other DTCs stored, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If there are no other DTCs stored, go to next step.
3. Perform a visual and physical inspection. If problem was found, repair as necessary. After repairs, go to step 6 . If problem was not found, go to next step.
4. With engine idling, install scan tool. If misfire current counter is incrementing on cylinder that had misfire DTC, go to next step. If misfire current counter is not incrementing on cylinder that had misfire DTC, go to step 6 .
5. Turn engine off. Disconnect fuel injector harness connectors. Install Spark Tester (J 26792) on spark plug wire for cylinder that indicated a misfire. Disconnect other spark plug wire from same ignition coil and install jumper wire between spark plug connector of ignition coil housing and ground. Crank engine with remaining spark plug cables still connected. If spark tester sparks, go to step 8 . If spark tester does not spark, go to step 9 .
6. Turn ignition on, engine off. Review FREEZE FRAME data. Note parameters. Operate vehicle within FREEZE FRAME conditions and code enable criteria. If misfire current counter is incrementing on cylinder that indicated a misfire, go to step 5 . If misfire current counter is not incrementing on cylinder that indicated a misfire, go to next step.
7. If repair was made from visual and physical inspection, go to step 30 . If repair was not made from visual and physical inspection, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
8. Remove spark plug from misfiring cylinder. Exchange spark plug with a spark plug from a known-good cylinder. Reconnect fuel injector harness connector. Run vehicle within misfire conditions as noted from FREEZE FRAME data. If misfire current counter is incrementing on cylinder that indicated a misfire, go to step 13 . If misfire current counter is not incrementing on cylinder that indicated a misfire, go to step 22 .
9. Remove spark plug cable from misfiring cylinder. Using DVOM, measure resistance of spark plug cable. If spark plug cable resistance is less than 1000 ohms per inch, go to next step. If spark plug cable resistance is not less than 1000 ohms per inch, go to step 23 .
10. Remove ignition coil from cylinder that did not fire. Using DVOM, measure of ignition coils secondary resistance. If resistance is 5-8 k/ohms, go to next step. If resistance is not 5-8 k/ohms, go to step 24 .
11. Replace ignition coil with a known-good one. Crank engine. Inspect for spark. If spark occurred on spark tester, go to step 24 . If spark did not occur on spark tester, go to next step.
12. Check ICM 6-pin harness connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 30 . If problem was not found, go to step 25 .
13. Turn engine off. Disconnect 4 fuel injector harness connectors from injectors. Install Injector Test Light (J 34730-405) on injector harness connector for misfiring cylinder. Crank engine and note injector test light. If injector test light blinks, go to next step. If injector test light does not blink, go to step 15 .
14. Perform injector coil test and injector balance test procedure. See INJECTOR COIL TEST and INJECTOR BALANCE TEST in appropriate SYSTEM & COMPONENT TESTING article. If fuel injector is okay for cylinder that had indicated a misfire, go to step 28 . If fuel injector is not okay for cylinder that had indicated a misfire, go to step 29 .
15. Disconnect injector test light. Using test light connected to ground, probe misfiring cylinder fuel injector harness connector terminal "A" (Gray wire). Crank engine. If test light is on, go to next step. If test light is off, go to step 27 .
16. Connect test light to ground. Disconnect fuel injector harness connectors. Turn ignition on, engine off. Probe fuel injector harness connector "B". See «INJECTOR CONTROL CIRCUIT WIRE COLOR»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) table under DTC P0201-P0204: INJECTOR CONTROL CIRCUIT for wire colors for cylinder that indicated a misfire. If test light remained off, go to next step. If test light did not remain off, go to step 26 .
17. Connect test light to battery voltage. Probe fuel injector connector terminal "B" of cylinder that indicated a misfire. If test light remained off, go to next step. If test light did not remain off, go to step 19 .
18. Check fuel injector harness connector and PCM harness connectors for open circuit. If problem was found, go to step 20 . If problem was not found, go to step 21 .
19. Check fuel injector control circuit for short to ground for cylinder that indicated a misfire. If problem was found, repair as necessary. After repairs, go to step 30 . If problem was not found, go to next step.
20. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 30 .
21. Repair connector or connections. After repairs, go to step 30 .
22. Replace malfunctioning spark plug. After repairs, go to step 30 .
23. Replace spark plug cable. After repairs, go to step 30 .
24. Replace defective ignition coil. After repairs, go to step 30 .
25. Replace ICM. After repairs, go to step 30 .
26. Check misfiring cylinder fuel injector control circuit for short to voltage. If problem was found, repair as necessary. After repairs, go to step 30 . If problem was not found, go to step 20 .
27. Repair open in Gray wire between fuel injector and underhood fuse block. After repairs, go to step 30 .
28. Repair basic engine problem. See appropriate article in ENGINES. After repairs, go to step 30 .
29. Replace malfunctioning fuel injector. After repairs, go to step 30 .
30. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
31. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

An intermittent DTC can also be the result of a defective reluctor wheel. Remove crankshaft sensor and inspect reluctor wheel through crankshaft sensor mount hole. Inspect for porosity and condition of reluctor wheel.

DTC P0301-P0304: CYLINDER MISFIRE DETECTED (2.4L)

Note. For circuit reference, see WIRING DIAGRAMS article.

Note. Last number of DTC refers to cylinder number that set DTC.

PCM uses information from Ignition Control (ICM) module and Camshaft Position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring variations in crankshaft rotation speed for each cylinder, PCM is able to detect individual misfire events. A misfire rate that is high enough can cause 3-way catalytic converter to overheat under certain conditions. Malfunction Indicator Lamp (MIL) will flash on and off when conditions for 3-way catalytic converter overheating are present.

1. DTCs P0105, P0107, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0171, P0172, P0325, P0335, P0341, P0342, P0502, P0503, P0506, P0507, P0601, P0740, P0742, P1133, or P1621 are not set.
2. Engine speed is 469-6400 RPM.
3. Battery voltage is 9-17 volts.
4. Engine Coolant Temperature (ECT) is 20-254°F (-7 to 123°C).
5. Engine has been running more than 5 seconds.
6. Throttle Position (TP) has not increased more than 8 percent in one second.
7. TP has not decreased more than 1.5 percent in one second.

DTC sets when PCM is detecting a crankshaft rotation speed variation indicating a misfire rate sufficient to cause emissions levels to exceed mandated standard.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on, engine off. Install scan tool. If any injector DTCs are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions). If no injector DTCs are set, go to next step.
3. Turn ignition off. Perform a visual/physical inspection. If problem was found, repair as necessary. After repairs, go to step 25. If problem was not found, go to next step.
4. Start engine. Idle engine. Observe MISFIRE CURRENT COUNTERS with scan tool. If misfire current counter is incrementing for affected cylinder, go to next step. If misfire current counter is not incrementing for affected cylinder, go to step 6.
5. Turn ignition off. Remove air cleaner outlet resonator assembly. Disconnect all fuel injector electrical connectors. Disconnect ICM 11-pin electrical connector. Temporarily remove ignition coil and electronic ICM assembly. Reconnect ICM 11-pin electrical connector. Install Spark Plug Jumper Wires (J 36012-A) into spark plug boot assemblies. Install (Spark Plug Tester J 26792) on spark plug jumper wire for affected cylinder. Remove spark plug boot assembly from companion cylinder of ignition coil housing. Install jumper wire between companion spark plug connector of ignition coil housing and ground. Connect jumper wire to ICM assembly to ground. Crank engine with remaining spark plugs wires still connected. If spark tester sparks, go to step 7. If spark tester does not spark, go to step 10.
6. Turn engine off, ignition on. Review FREEZE FRAME data and record parameters. Start engine. Operate vehicle within FREEZE FRAME conditions and code enable criteria. Observe MISFIRE CURRENT COUNTERS with scan tool. If MISFIRE CURRENT COUNTER for affected cylinder is incrementing, go to step 5. If MISFIRE CURRENT COUNTER for affected cylinder is not incrementing, go to step 25.
7. Turn ignition off. Remove spark plug from affected cylinder. Exchange spark plug with a spark plug from a known-good cylinder. Reconnect all fuel injector electrical connectors. Install spark plug boot assembly to affected cylinder spark plug connection at ignition coil housing. Reconnect spark plug jumper wire to spark plug boot assembly. Start engine. Run vehicle when misfire was present. If MISFIRE CURRENT COUNTER for affected cylinder is incrementing, go to next step. If MISFIRE CURRENT COUNTERS for affected cylinder is not incrementing, go to step 9.
8. Check for a leaking fuel injector. See «DTC P0201-P0204: INJECTOR CONTROL CIRCUIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__dtc-p0201-p0204-injector-control-circuit). If fuel injector is okay, check and repair basic engine problem. See appropriate article in ENGINES. After repairs, go to step 25.
9. Turn ignition off. Replace spark plug. After repairs, go to step 25.
10. Turn ignition off. Remove spark plug boot assemblies from affected coil. Disconnect ICM 11-pin electrical connector. Connect DVOM between secondary ignition coil terminals at ignition coil housing. If resistance is 4-8 k/ohms, go to next step. If resistance is not 4-8 k/ohms, go to step 12.
11. Remove coil housing. Disconnect coil harness electrical connector from ICM. Reconnect ICM 11 pin electrical connector. Using test light connected to battery voltage, probe affected cylinder coil control terminal (White wire). Crank engine while watching test light. If test light blinks, go to step 13. If test light does not blink, go to step 14.
12. Remove affected cylinder ignition coil from ignition coil housing. Recheck resistance between secondary terminals of affected cylinder ignition coil. If resistance is 4-8 k/ohms, go to step 15. If resistance is not 4-8 k/ohms, go to step 16.
13. Remove ignition coils from ignition coil housing. Disconnect ignition coil electrical connector from ignition coils. Reconnect ignition coil electrical connector to ICM. Connect test light to ground. Turn ignition on, engine off. Probe ignition feed circuit (Brown wire) to ignition coils at both of ignition coil electrical connector terminals "B" with test light. If test light is on for both circuits, go to step 19. If test light is not on for both circuits, go to step 20.
14. Turn ignition off. Disconnect ICM 11-pin electrical connector. Visually inspect ICM 11-pin electrical connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 25. If problem was not found, go to step 17.
15. Check and replace as necessary, ignition coil spring for affected coils and ignition coil housing. After repairs, go to step 25.
16. Replace affected cylinders ignition coil. After repairs, go to step 25.
17. Reconnect ICM 11-pin electrical connector. Disconnect PCM connector C1. Reconnect affected cylinder spark plug boot assembly to spark plug connector at ignition coil housing. Reconnect spark plug jumper wire to affected cylinder spark plug boot assembly. Reconnect spark tester on affected cylinder spark plug wire. Connect jumper wire to companion cylinder spark plug connector at ignition coil housing to ground. Turn ignition on, engine off. Connect test light to battery voltage. Momentarily touch PCM connector C1 terminal No. 26 (White wire) for 1/4 coil or terminal No. 25 (Orange wire) for 2/3 coil for affected cylinder. (Scheme 5) A spark should be present when test light is removed from ICM timing control circuit. If there is a spark present when you remove test light from ICM timing control circuit, go to step 23. If there is no spark present when you remove test light from ICM timing control circuit, go to next step.
18. Turn ignition off. Check ICM timing control circuit (White wire for 1/4 coil or Orange wire for 2/3 coil) for open circuit, short to ground, short to voltage or poor electrical connection at ICM. If problem was found, repair as necessary. After repairs, go to step 25. If problem was not found, go to step 22.
19. Check affected cylinder coil control circuit for poor electrical connection to ICM and ignition coil, open circuit, short to ground or short to voltage. If problem was found, repair as necessary. After repairs, go to step 25. If problem was not found, go to step 21.
20. Turn ignition off. Repair open in ignition voltage circuit (Brown wire) between 1/4 and 2/3 ignition coils and ICM. After repairs, go to step 25.
21. Turn ignition off. Check ignition voltage circuit (Brown wire) for poor connection at affected cylinder ignition coil. If electrical connection is okay, replace spark plug boot assembly. After repairs, go to step 25.
22. Turn ignition off. Replace ICM. See IGNITION CONTROL MODULE (IDI) under appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 25.
23. Turn ignition off. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 25. If problem was not found, go to next step.
24. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
25. Reconnect all previously disconnected components. Connect all fuel injector electrical connectors. Install air cleaner outlet resonator assembly. Using scan tool, clear DTCs. Start engine. Idle engine at normal operating temperature. Operate vehicle within code enable criteria for this DTC and DTC P0420. If DTC does not reset, go to next step.
26. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

An intermittent can also be the result of a defective reluctor wheel. Remove crankshaft sensor and inspect reluctor wheel through sensor mount hole. Check for porosity and condition of wheel.

Verify electronic Ignition Control Module (ICM) 11-pin harness connector terminal "K", ground circuit should have less than 0.5 ohm of resistance.

When checking electrical terminal connections using test light or DVOM, a malfunctioning electrical terminal connection maybe cleaned and not detected as a problem. You may also clean a corroded or dirty electrical terminal connection when disconnecting and reconnecting any electrical connector.

DTC P0325: KNOCK SENSOR CIRCUIT (2.2L)

Note. For circuit reference, see WIRING DIAGRAMS article.

Knock Sensor (KS) produces an AC voltage at all engine speeds and loads. PCM then adjusts spark timing based on amplitude and frequency of KS signal. PCM uses KS signal to calculate average voltage. Then PCM assigns a voltage value. PCM checks knock sensor and related wiring by comparing actual knock signal to assigned voltage range. A normal KS signal should stay outside assigned voltage range. This DTC will set if KS signal is within assigned voltage range or not present, or if PCM malfunctions in a manner that will not allow proper diagnosis of KS system.

1. DTCs P0122 or P0123 are not set.
2. Engine run time is more than 20 seconds.
3. Engine Coolant Temperature (ECT) is more than 131°F (56°C).
4. Engine speed is 1600-6400 RPM.
5. Manifold Absolute Pressure (MAP) is more than 60 kPa.

DTC sets when KS voltage and variation is not within normally expected ranges for more than 15 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate engine within code enable criteria or close to FREEZE FRAME/FAILURE RECORDS data that you observed. If scan tool indicates diagnostic failed this ignition cycle, go to next step. If scan tool does not indicate diagnostic failed this ignition cycle, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
3. Disconnect KS connector. (Scheme 6) Set DVOM to 400 k/ohm scale. Measure resistance of KS using DVOM connected to ground. If resistance is 90-110 k/ohms, go to next step. If resistance is not 90-110 k/ohms, go to step 6.
4. With DVOM still connected, set DVOM to measure AC frequency. Tap on engine block near appropriate KS while observing signal indicated on DVOM. If any signal is indicated on DVOM while tapping on engine block near KS, go to next step. If no signal is indicated on DVOM while tapping on engine block near KS, go to step 6.
5. Disconnect PCM connector. Check Dark Blue wire between PCM and KS for open, short to voltage or short to ground. If problem was found, repair as necessary. After repairs, go to step 9. If problem was not found, go to step 7.
6. Replace KS. After repairs, go to step 9.
7. Check for poor connection at PCM or KS harness connector. If problem was found, repair as necessary. After repairs, go to step 9. If problem was not found, go to next step.
8. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
9. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
10. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

Inspect KS for proper installation. A KS that is loose or over torqued may cause DTC to set.

Inspect and correct any abnormal engine noise before using this procedure.

DTC P0325: KNOCK SENSOR CIRCUIT (2.4L)

Note. For circuit reference, see WIRING DIAGRAMS article.

Knock Sensor (KS) produces an AC voltage at all engine speeds and loads. PCM then adjusts spark timing based on amplitude and frequency of KS signal. PCM uses KS signal in order to calculate average voltage. Then PCM assigns a voltage value. PCM checks KS and related wiring by comparing actual knock signal to assigned voltage range. A normal KS signal should stay within assigned voltage range.

1. DTCs P0122 or P0123 are not set.
2. Engine Coolant Temperature (ECT) is more than 140°F (70°C).
3. Engine run time is more than 20 seconds.
4. Manifold Absolute Pressure (MAP) is more than 60 kPa.
5. Engine speed is 1800-6400 RPM.

DTC sets when KS is outside assigned range, or KS is not present.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate engine within code enable criteria or close to FREEZE FRAME/FAILURE RECORDS data that you observed. If scan tool indicates diagnostic failed this ignition cycle, go to next step. If scan tool does not indicate diagnostic failed this ignition cycle, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
3. Turn ignition on, engine off. Using scan tool, save FREEZE FRAME/FAILURE RECORDS data stored when DTC set. Turn ignition off and wait 30 seconds. Disconnect PCM connector. Connect DVOM between PCM connector C1 terminals No. 32 (Gray wire) and No. 34 (Dark Blue wire). (Scheme 5) Observe frequency while tapping on engine block with a non-metallic object. If DVOM displays a fluctuating frequency while tapping on engine block, go to step 6. If DVOM does not display a fluctuating frequency while tapping on engine block, go to next step.
4. Disconnect KS connector. Check for open in Dark Blue wire or Gray wire between KS and PCM. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to next step.
5. Check KS connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 9.
6. Check Dark Blue wire between KS and PCM for short to ground or short to voltage. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to next step.
7. Check Gray wire between KS and PCM for short to ground or short to voltage. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to next step.
8. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 10.
9. Replace KS. After repairs, go to step 12.
10. Check KS and harness connector for damage. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to next step.
11. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
12. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
13. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

1. Knock sensor must be torqued correctly to 19 ft. lbs. (25 N.m).
2. Mounting between sensor and engine must be free of burrs, casting flash, and foreign material.
3. Knock sensor head is clear from hoses, brackets, and engine wiring.

DTC P0336: CRANKSHAFT POSITION (CKP) SENSOR PERFORMANCE (2.2L - GASOLINE)

Note. For circuit reference, see WIRING DIAGRAMS article.

Crankshaft Position (CKP) sensor signal indicates crankshaft speed and position. CKP sensor is connected directly to PCM.

1. DTC P0341 is not set.
2. Engine is running.

DTC sets when CKP re-sync counter goes more than 15 times within 4 minutes and 15 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Attempt to start engine. If engine starts, go to next step. If engine does not start, see NO START DIAGNOSIS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
3. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or close to FREEZE FRAME/FAILURE RECORDS data that you observed. If DTC failed this ignition cycle, go to next step. If DTC did not fail this ignition cycle, go to step 5 .
4. With engine running, wiggle electrical connectors of PCM and CKP and related circuits, while listening for engine to stumble. If engine stumbles, go to step 6 . If engine does not stumble, go to step 7 .
5. Operate any non-engine related electronic component on vehicle. Observe MED. RESOLUTION RESYNC COUNTER with scan tool. If MED. RESOLUTION RESYNC COUNTER on scan tool increments while operating any non-engine related electronic components, go to step 9 . If MED. RESYNC COUNTER on scan tool does not increment while operating any non-engine related electronic components, go to step 4 .
6. Turn ignition off. Check for a poor electrical terminal connection or replace terminal in circuit which caused engine to stumble. After repairs, go to step 12 .
7. If MIL illuminated in step 3 , go to next step. If MIL did not illuminate in step 3 , go to step 12 .
8. Turn ignition off. Check PCM and CKP sensor for rubbed through wire insulation or wiring being pinched. If problem was found, repair as necessary. After repair, go to step 12 . If problem was not found, go to step 10 .
9. Turn ignition off. Repair circuitry of malfunctioning or interfering component. Move any wiring that is causing interference away from CKP wiring harness. After repairs, go to step 12 .
10. Replace CKP sensor. See CRANKSHAFT POSITION SENSOR (DIS & IDI) in appropriate REMOVAL, OVERHAUL & INSTALLATION article. Idle engine for 5 minutes, or until MIL turns on. If MIL turns on, go to next step. If MIL does not turn on, go to step 12 .
11. Turn ignition off. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. Idle engine for 5 minutes, or until MIL turns on. If MIL turns on, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) . If MIL does not turn on, go to next step.
12. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
13. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

1. If the complaint was Engine Cranks But Will Not Run, you may set DTC P0336 when attempting to start the engine more than 15 times and the ignition is not turned OFF between attempts.
2. An intermittent problem may be caused by the following conditions: Rubbed-through wire insulation. Poor electrical connections. Broken wire inside insulation.
3. Thoroughly inspect any suspected circuitry for the following conditions: Backed-out terminals. Improper mating. Broken locks. Improperly formed terminals. Damaged terminals. Poor terminal-to-wire connections. Physical damage to the wiring harness.
4. An intermittent can also be the result of a defective reluctor wheel. Remove crankshaft sensor and inspect reluctor wheel through hole.

Crankshaft Position (CKP) sensor is connected to Ignition Control (IC) module. CKP sensor is mounted near crankshaft and monitors a toothed crankshaft reluctor wheel mounted to crankshaft. When crankshaft rotates, a signal is induced into CKP sensor. Based upon signal received from CKP sensor, IC module supplies a CKP signal on CKP 7X reference circuit. For each one engine revolution, IC module pulses CKP 7X reference circuit 7 times. Powertrain Control Module (PCM) and Alternate Fuel Engine Control Unit (AF ECU) use CKP 7X signal to determine engine speed, crankshaft position and cylinder misfire condition.

For DTC to run, the following conditions must be met

1. Engine is operating on alternative fuel for an initial failure. AF ECU will run this DTC in gasoline mode after an initial alternative fuel mode failure.
2. MAP sensor signal indicates 31.07 in. Hg (105.23 kPa) or less.
3. Cam signal monitored indicates engine is cranking or running.

DTC will set when AF ECU detects no CKP reference signal when a cam sensor signal is detected. When DTC is set, engine will switch over to gasoline operation.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Attempt to start engine. If engine starts and runs, go to next step. If engine does not start and run, go to NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - CARS - EXCEPT METRO & PRIZM article.
3. Using scan tool, communicate with PCM. Check for DTCs stored in PCM. If any PCM DTCs are set, diagnose those DTCs first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions). If no PCM DTCs are set, go to next step.
4. Using scan tool, communicate with AF ECU. Clear DTCs stored in AF ECU. Turn ignition off for 10 seconds. Start engine and allow to idle. Recheck for DTCs in AF ECU. If DTC P0336 resets, go to step 6. If DTC P0336 does not reset, go to next step.
5. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
6. Check for open or high resistance in Purple/White wire between AF ECU Blue connector C001 terminal No. 18 and splice S011. (Scheme 3) S011 is located approximately 6.5" (16.5 cm) from IAT sensor harness breakout, towards oxygen sensor harness breakout. Repair as necessary. After repairs, go to step 8. If circuit is okay, go to next step.
7. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to next step.
8. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may also be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

DTC P0336: CRANKSHAFT POSITION (CKP) SENSOR PERFORMANCE (2.4L)

Note. For circuit reference, see WIRING DIAGRAMS article.

Crankshaft Position (CKP) sensor signal indicates crankshaft speed and position. CKP sensor is connected directly to Ignition Control Module (ICM).

1. Engine is running.
2. DTC P0341 is not set.

DTC sets when CKP resync counter goes more than 15 times within 4 minutes and 15 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Attempt to start engine. If engine starts, go to next step. If engine does not start, see NO START DIAGNOSIS under appropriate BASIC DIAGNOSTIC PROCEDURES article.
3. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or close to FREEZE FRAME/FAILURE RECORDS data that you observed. If DTC failed this ignition cycle, go to next step. If DTC did not fail this ignition cycle, go to step 5 .
4. With engine running, wiggle electrical connectors of PCM, ICM and CKP and related circuits, while listening for engine to stumble. If engine stumbles, go to step 6 . If engine does not stumble, go to step 7 .
5. Operate any non-engine related electronic component on vehicle. Observe MED. RESOLUTION RESYNC COUNTER with scan tool. If MED. RESOLUTION RESYNC COUNTER on scan tool increments while operating any non-engine related electronic components, go to step 9 . If MED. RESYNC COUNTER on scan tool does not increment while operating any non-engine related electronic components, go to step 4 .
6. Turn ignition off. Check for a poor electrical terminal connection or replace terminal in circuit which caused engine to stumble. After repairs, go to step 13 .
7. If MIL illuminate in step 3 , go to next step. If MIL did not illuminate in step 3 , go to step 13 .
8. Turn ignition off. Check PCM, ICM and CKP sensor for rubbed through wire insulation or wiring being pinched. If problem was found, repair as necessary. After repair, go to step 13 . If problem was not found, go to step 10 .
9. Turn ignition off. Repair circuitry of malfunctioning or interfering component. Move any wiring that is causing interference away from CKP wiring harness. After repairs, go to step 13 .
10. Replace CKP sensor. See CRANKSHAFT POSITION SENSOR (DIS & IDI) under appropriate REMOVAL, OVERHAUL & INSTALLATION article. Start engine. Idle for 5 minutes, or until MIL turns on. If MIL turns on, go to next step. If MIL does not turn on, go to step 13 .
11. Turn ignition off. Replace ICM. See IGNITION CONTROL MODULE (IDI) under appropriate REMOVAL, OVERHAUL & INSTALLATION article. Start engine. Idle engine for 5 minutes, or until MIL turns on. If MIL turns on, go to next step. If MIL does not turn on, go to step 13 .
12. Turn ignition off. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. Start engine. Idle for 5 minutes, or until MIL turns on. If MIL turns on, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) . If MIL does not turn on, go to next step.
13. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
14. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

1. If complaint was engine cranks but will not run, you may set a DTC P0336 when attempting to start engine more than 15 times, and when ignition is not turned off between attempts.
2. An intermittent problem may be caused by the following conditions: Rubbed-through wire insulation. Poor electrical connections. Broken wire inside insulation.
3. Thoroughly check any suspected circuitry for the following conditions: Backed-out terminals. Improper mating. Broken locks. Improperly formed terminals. Damaged terminals. Poor terminal-to-wire connections. Physical damage to wiring harness.
4. An intermittent can also be the result of a defective reluctor wheel. Remove crankshaft sensor, and inspect reluctor wheel through hole.

DTC P0340: CAMSHAFT POSITION SENSOR CIRCUIT - LOW INPUT

Note. For circuit reference, see WIRING DIAGRAMS article.

Camshaft Position (CMP) sensor indicates camshaft position so PCM can determine which cylinder is misfiring when a misfire is present. With engine running, CMP activity counter will increment. Whenever PCM receives an intermittent signal from CMP, then CMP resync counter will increment.

1. Engine is running.

DTC sets when there is no change in cam activity for 30 crankshaft revolutions.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Start and idle engine. Using scan tool, monitor CMP ACTIVE COUNTER. If scan tool indicates CMP ACTIVE COUNTER is incrementing, go to next step. If scan tool does not indicate CMP ACTIVE COUNTER is incrementing, go to step 4.
3. Observe FREEZE FRAME/FAILURE RECORDS and data. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or as close as possible to FREEZE FRAME/FAILURE RECORDS data that you observe. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Disconnect CMP sensor connector. (Scheme 6)or (Scheme 7). Turn ignition on, engine off. Using DVOM connected to ground, measure voltage on CMP sensor connector terminal "C" (Red wire). see scheme 13 If battery voltage is present, go to step 6. If battery voltage is not present, go to next step.
5. Turn ignition off. Disconnect PCM connector C2. Check Red wire between CMP sensor and PCM for short to ground or open. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 12.
6. Using test light connected to battery voltage, probe CMP sensor connector terminal "B" (Pink/Black wire). If test light is on, go to step 8. If test light is off, go to next step.
7. Turn ignition off. Disconnect PCM connector C2. Check Pink/Black wire between CMP sensor and PCM for open. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 12.
8. Start engine. Observe CMP ACTIVE COUNTER on scan tool. Connect fused jumper wire (5-amp) to battery voltage and momentarily touch CMP sensor connector terminal "A" (Brown/White wire) 5 times for a duration of one second each. If CMP ACTIVE COUNTER changes each time signal circuit is touched, go to step 14. If CMP ACTIVE COUNTER does not change each time signal circuit is touched, go to next step.
9. If fuse in jumper wire opened, go to step 10. If fuse in jumper wire did not open, go to next step.
10. Check signal circuit (Brown/White wire) of CMP sensor for short to voltage or open. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 12.
11. Check Brown/White wire between CMP sensor and PCM for short to ground. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 12.
12. Check PCM connectors for poor connections. at the PCM. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 13.
13. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 16.
14. Check CMP sensor connector for poor connections. at the CMP sensor. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to next step.
15. Replace CMP sensor. See CAMSHAFT POSITION SENSOR under appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
16. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
17. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

1. Whenever PCM sees less than 15 re-syncs in 256 seconds, counter resets to zero. When a poor connection is present, cam sensor active counter stops incrementing, and cam sensor resync counter starts to increment.
2. Inspect wiring harness for damage. If harness appears to be okay, observe CMP resync counter on scan tool while moving connectors and wiring harnesses related to CMP sensor. If CMP resync counter still does not count, then while still observing scan tool, operate any non-engine related electrical components on vehicle. A change in display will indicate location of malfunction.
3. A defective reluctor wheel or a cracked or damaged CMP sensor can result in an intermittent. Remove camshaft sensor and inspect for any damage. With CMP sensor removed, you can also inspect reluctor wheel through hole. Check porosity and condition of wheel. Edges must be square, look for a nicked or damaged wheel.

DTC P0341: CAMSHAFT POSITION SENSOR CIRCUIT PERFORMANCE

Note. For circuit reference, see WIRING DIAGRAMS article.

Camshaft Position (CMP) sensor indicates camshaft position so PCM can determine which cylinder is misfiring when a misfire is present. Whenever PCM receives an intermittent signal from CMP, CMP resync counter will increment.

1. Engine is running.

DTC sets when PCM sees more than 15 CMP sensor re-syncs in 256 seconds (4 minutes 16 seconds).

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on, engine off. Connect scan tool. If any other DTCs are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions). If no other DTCs are set, go to next step.
3. Start engine. Allow engine to idle. Observe CMP RESYNC COUNTER with scan tool. If CMP RESYNC COUNTER is incrementing, go to next step. If CMP RESYNC COUNTER is not incrementing, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Disconnect CMP sensor connector. (Scheme 6)or (Scheme 7). Start engine. Observe CMP Resync on scan tool. If CMP resync counter stopped incrementing, go to next step. If CMP resync counter did not stop incrementing, go to step 7.
5. Turn ignition off. Check CMP connector for poor connections. If problem was found, repair as necessary. After repair, go to step 9. If problem was not found, go to next step.
6. Replace CMP sensor. See CAMSHAFT POSITION SENSOR under appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 9.
7. Disconnect PCM connectors. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 9. If problem was not found, go to next step.
8. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
9. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
10. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

If PCM sees less than 15 re-syncs in 256 seconds, the counter is reset to zero. When a faulty electrical connection is present, CMP reference activity counter will stop incrementing and CMP Resync Counter will increment.

DTC P0420: TWC SYSTEM - LOW EFFICIENCY (2.2L)

Note. For circuit reference, see WIRING DIAGRAMS article.

A 3-way catalytic (TWC) converter is used in order to control exhaust emissions of Hydrocarbons (HC), Carbon Monoxide (CO), and oxides of nitrogen (NOx). The catalyst within converter promotes a chemical reaction which oxidizes HC and CO that is present in exhaust gas. This process will convert HC and CO into a harmless water vapor and CO2 and will reduce NOx, converting NOx into nitrogen. The catalytic converter also has ability to store oxygen. PCM has capability to monitor this process by using a Heated Oxygen Sensor (HO2S) which is in exhaust stream past 3-way catalytic converter. HO2S produces an output signal which indicates oxygen storage capacity of catalyst. This in turn indicates the catalyst's ability to convert the exhaust emissions effectively. PCM monitors catalyst efficiency by first allowing catalyst to heat, waiting for a stabilization period while engine is idling. Then, PCM adds and removes fuel while monitoring reaction of HO2S. When catalyst is functioning properly, HO2S2 response to extra fuel is slow compared to the O2S1. When HO2S2 response is close to that of O2S1, oxygen storage capability or efficiency of catalyst is considered to be bad and MIL will illuminate.

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0131, P0132, P0133, P0134, P0137, P0138, P0140, P0141, P0171, P0172, P0201-P0204, P0300, P0301-P0304, P0325, P0336, P0340, P0341, P0440, P0442, P0446, P0452, P0453, P0480, P0502, P0503, P0506, P0507, P0601, P0602, P1133, P1336, P1441, or P1621 are not set.
2. Engine has been running more than 530 seconds after throttle has moved.
3. BARO is more than 72 kPa.
4. Vehicle is in closed loop operation.
5. Vehicle has been driven at more than 1000 RPM for more than 35 seconds if vehicle has an automatic transmission.
6. Vehicle has been driven at more than 1000 RPM for more than 45 seconds if vehicle has a manual transmission.
7. Battery voltage is more than 9 volts.

With vehicle stopped

1. Engine is idling less than 150 RPM from desired idle.
2. Vehicle is in Drive (automatic transmission) or in Neutral (manual transmission).
3. Throttle Position (TP) is zero percent.
4. Engine Coolant Temperature (ECT) is 56-257°F (69-125°C).
5. Intake Air Temperature (IAT) is -4 to 176°F (-20 to 80°C).
6. Short Term (ST) fuel trim is between -28 to +28 percent.
7. Catalytic temperature is more than 950°F (510°C).
8. Specified conditions are present for up to 30 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on, engine off. Install scan tool. If any component DTCs are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If no component DTCs are set, go to next step.
3. Turn ignition off. Check exhaust system for leaks and rear heated oxygen sensor (HO2S2) for leaks. If problem was found, repair as necessary. After repairs, go to next step. If problem was not found, go to step 5 .
4. Repair exhaust system as necessary. After repairs, go to step 6 .
5. Replace 3-way catalytic converter. After repairs, go to next step.
6. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
7. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

Catalyst test may abort due to a change in engine load. Do not change engine load, that is, do not reset A/C, coolant fan, or heater motor while a catalyst test is in progress.

Certain conditions may cause a catalytic converter to degrade. These conditions may include the following conditions

1. Engine misfire.
2. High engine oil or high coolant consumption.
3. Retarded spark timing.
4. Weak spark.
5. Lean fuel system.

DTC P0420: TWC SYSTEM - LOW EFFICIENCY (2.4L)

Note. For circuit reference, see WIRING DIAGRAMS article.

A 3-way catalytic converter is used in order to control exhaust emissions of Hydrocarbons (HC), Carbon Monoxide (CO), and oxides of nitrogen (NOx). Catalyst within converter promotes a chemical reaction which oxidizes HC and CO present in exhaust gas. This converts HC and CO into harmless water vapor and carbon dioxide, and reduces NOx, converting NOx into nitrogen. Catalytic converter also has ability to store oxygen. PCM has capability to monitor this process by using a Heated Oxygen Sensor (HO2S) which is in the exhaust stream past 3-way catalytic converter. HO2S produces an output signal which indicates oxygen storage capacity of catalyst. This in turn indicates catalyst's ability to convert exhaust emissions effectively. PCM monitors catalyst efficiency by first allowing catalyst to heat up, waiting for a stabilization period while engine is idling. Then, PCM adds and removes fuel while monitoring reaction of HO2S. When catalyst is functioning properly, HO2S2 response to extra fuel is slow compared to O2S1. When HO2S2 response is close to that of O2S1, oxygen storage capability or efficiency of catalyst is considered to be deficient and MIL will illuminate.

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0131, P0132, P0133, P0134, P0137, P0138, P0140, P0141, P0171, P0172, P0201-P0204, P0300, P0325, P0336, P0340, P0341, P0440, P0442, P0446, P0452, P0453, P0480, P0481, P0502, P0503, P0506, P0507, P0601, P0602, P1133, P1171, P1336, P1441, or P1621 are not set.
2. Engine has been running more than 520 seconds after throttle has moved.
3. Barometric (BARO) pressure is more than 72 kPa.
4. Vehicle is in closed loop operation.
5. Vehicle has been driven at more than 1200 RPM for more than 45 seconds.
6. Battery voltage is more than 9 volts.

Then, with vehicle stopped

1. Engine is idling at less than 150 RPM from desired idle.
2. Vehicle is in Drive.
3. Throttle Position (TP) is zero percent.
4. Engine Coolant Temperature (ECT) is between 156-257°F (69-125°C).
5. Intake Air Temperature (IAT) is -4-176°F (-20-80°C).
6. Short Term (ST) fuel trim is 93-163 (-28 percent to +28 percent).
7. Predicted catalyst temperature is 923-1117.5°F (495-603°C).
8. Specified conditions are present for up to 30 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on, engine off. Install scan tool. If any other DTCs are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If no other DTCs are set, go to next step.
3. Using scan tool, clear DTCs. Operate vehicle within code enable criteria. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
4. Turn ignition off. Visually and physically inspect exhaust system and rear heated oxygen sensor (HO2S2) for leaks. If problem was found, repair as necessary. After repairs, go to step 6 . If problem was not found, go to next step.
5. Replace 3-way catalytic converter. After repairs, go to next step.
6. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If scan tool indicates diagnostic ran and passed, go to next step.
7. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

Catalyst test may abort due to a change in engine load. Do not change engine load while a catalyst test is in progress.

Certain conditions may cause a catalytic converter to degrade. These conditions may include the following items

1. Engine misfire.
2. High engine oil or coolant consumption.
3. Retarded spark timing.
4. Weak spark.
5. Lean fuel system.

DTC P0440: EVAP SYSTEM

Note. For circuit reference, see WIRING DIAGRAMS article.

EVAP large leak test applies vacuum to Evaporative Emission (EVAP) system and monitors vacuum decay. PCM monitors the Fuel Tank Pressure (FTP) sensor signal to determine vacuum decay rate. At an appropriate time, PCM turns EVAP canister purge valve on (open) and EVAP vent valve on (closed). This allows engine to draw a vacuum on EVAP system. At a calibrated time, or vacuum level, PCM turns purge valve off (closed), sealing system, and monitors FTP sensor input in order to determine EVAP system vacuum. If system is unable to achieve calibrated vacuum level, or vacuum level decreases too rapidly, DTC P0440 will set.

1. DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0452, or P0453 are not set. The ignition voltage is between 10 and 18 volts.
2. Barometric pressure is more than 75 kPa.
3. Fuel level is 15-85 percent.
4. Engine Coolant Temperature (ECT) is 39-86°F (4-30°C).
5. Intake Air Temperature (IAT) is 39-86°F (4-30°C).
6. Start-up ECT and IAT are within 16°F (9°C) of each other.
7. Vehicle Speed Sensor (VSS) is less than 75 MPH.

DTC sets when EVAP system is not able to achieve or maintain vacuum during diagnostic test.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. If DTCs P0446, P0452, P0453, or P1441 also set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions). If DTCs P0446, P0452, P0453, or P1441 are not also set, go to next step.
3. Inspect EVAP system for the following conditions: A loose, incorrect, faulty or missing fuel tank fill cap. Damaged or disconnected EVAP system purge lines. A damaged EVAP system component. A loose, missing or damaged service port dust cap and/or Schrader valve. If problem was found, repair as necessary. After repairs, go to step 31. If problem was not found, go to next step.
4. Using scan tool, clear DTCs. Command EVAP canister purge valve to 50 percent, and back to zero percent with scan tool. If you hear or feel a clicking from EVAP purge valve when it is commanded to 50 percent, go to next step. If you do not hear or feel a clicking from EVAP purge valve when it is commanded to 50 percent, go to step 6.
5. Using scan tool, command EVAP canister vent valve on and off. If you hear or feel a click as EVAP vent valve is commanded on and off, go to step 10. If you do not hear or feel a click as EVAP vent valve is commanded on and off, go to step 8.
6. Disconnect EVAP purge valve harness connector. (Scheme 6)or (Scheme 7). Turn ignition on, engine off. Connect test light between EVAP purge valve connector terminal "A" (Pink wire on "J" body and Brown wire on "N" body) and ground. If test light is on, go to next step. If test light is off, go to step 22.
7. Connect test light between EVAP purge valve connector terminals. Using scan tool, command EVAP purge valve to 50 percent and then to zero percent. If test light is on when EVAP purge valve is commanded to 50 percent and turns off when EVAP purge valve is commanded to zero percent, go to step 18. If test light is not on when EVAP purge valve is commanded to 50 percent and turns off when EVAP purge valve is commanded to zero percent, go to step 16.
8. Turn ignition on, engine off. Disconnect EVAP vent valve harness connector. EVAP vent valve is located near fuel tank under vehicle. Connect test light between EVAP vent valve connector terminal "A" (Pink wire on "J" body and Brown wire on "N" body) and ground. If test light is on, go to next step. If test light is off, go to step 23.
9. Connect test light between EVAP vent valve connector terminals. Using scan tool, command EVAP vent valve on. If test light is on when EVAP vent valve is commanded on, go to step 19. If test light is off when EVAP vent valve is commanded on, go to step 17.
10. Turn ignition off. Disconnect EVAP purge pipe from EVAP purge valve. Connect a vacuum gauge directly to EVAP purge connection of EVAP purge valve. Start engine. Increase engine speed to 1500 RPM. Using scan tool, command EVAP canister purge valve to 50 percent. If vacuum is at or more than 15 in. H2O, go to next step. If vacuum is less than 15 in. H2O, go to step 21.
11. Always zero EVAP pressure and vacuum (in. H2O) gauges on EVAP pressure/purge diagnostic station before proceeding with diagnosis. Reconnect EVAP purge pipe to EVAP canister purge valve. Install fuel tank cap adapter. Connect EVAP pressure/purge diagnostic station and vehicle fuel fill cap to fuel tank cap adapter. Turn ignition on, engine off. Using scan tool, seal EVAP system. Using EVAP diagnostic station, attempt to pressurize EVAP system to specified value. Rotate EVAP diagnostic station rotary switch to OFF/HOLD position. If you were able to obtain and hold 5 in. H2O for one minute, go to next step. If you were not able to obtain and hold 5 in. H2O for one minute, go to step 13.
12. Compare EVAP diagnostic station pressure gauge value to scan tool Fuel Tank Pressure (FTP) sensor value. If EVAP pressure/purge diagnostic station gauge value corresponds to FTP sensor value on scan tool, go to step 14. If EVAP pressure/purge diagnostic station gauge value does not correspond to FTP sensor value on scan tool, go to step 29.
13. Using EVAP pressure/purge diagnostic station, continuously attempt to pressurize EVAP system. Using ultrasonic leak detector, inspect for leaks in the following locations: EVAP system purge pipe. EVAP vapor pipe. EVAP vent hose/pipe. Fuel fill pipe/hose and fuel fill cap. EVAP canister. EVAP canister vent valve. EVAP canister purge valve. Fuel sender assembly and/or seal. FTP sensor seal. Fill limiter vent valve, pressure relief valve, rollover valves, and fuel tank. If problem was found, repair as necessary. After repairs, go to step 31. If problem was not found, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
14. Monitor EVAP pressure/purge diagnostic station pressure gauge. Disconnect EVAP purge pipe from EVAP canister. If EVAP pressure/purge diagnostic station gauge decreases to near zero in. H2O, go to step 24. If EVAP pressure/purge diagnostic station gauge does not decrease to near zero in. H2O, go to next step.
15. Observe pressure gauge on EVAP pressure/purge diagnostic station. Disconnect EVAP vapor pipe from EVAP canister. If EVAP pressure/purge diagnostic station gauge decrease to near zero in. H2O, go to step 28. If EVAP pressure/diagnostic station gauge does not decrease to near zero in. H2O, go to step 25.
16. Check Dark Green/White wire between EVAP purge valve and PCM for open or short to voltage. If problem was found, repair as necessary. After repairs, go to step 31. If problem was not found, go to step 20.
17. Check White wire between EVAP vent valve and PCM for open or short to voltage. If problem was found, repair as necessary. After repairs, go to step 31. If problem was not found, go to step 20.
18. Check EVAP purge control valve connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 31. If problem was not found, go to step 26.
19. Check EVAP vent valve connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 31. If problem was not found, go to step 27.
20. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 31. If problem was not found, go to step 30.
21. Inspect vacuum source to EVAP purge valve for blockage, cuts, or disconnects. If problem was found, repair as necessary. After repairs, go to step 31. If problem was not found, go to step 26.
22. Repair open or short to ground in Pink wire between EVAP purge valve and instrument panel fuse block on "J" bodies or Brown wire between EVAP purge valve and underhood fuse block on "N" bodies. After repairs, go to step 31.
23. Repair open or short to ground in Pink wire between EVAP vent valve and instrument panel fuse block on "J" bodies or Brown wire between EVAP vent valve and underhood fuse block on "N" bodies. After repairs, go to step 31.
24. Repair restriction in EVAP purge pipe. After repairs, go to step 31.
25. Repair restriction in EVAP vapor pipe. After repairs, go to step 31.
26. Replace EVAP purge valve. After repairs, go to step 31.
27. Replace EVAP vent valve. After repairs, go to step 31.
28. Replace EVAP canister. After repairs, go to step 31.
29. Replace FTP sensor. After repairs, go to step 31.
30. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 31.
31. Turn ignition on, engine off. Using scan tool, command EVAP vent valve on. Pressurize EVAP system to specified value using EVAP pressure/purge diagnostic station. Place control knob on EVAP pressure/purge diagnostic station to OFF/HOLD position. Monitor EVAP system pressure on EVAP pressure/purge diagnostic station for 5 minutes. If EVAP system pressure remains constant, go to next step. If EVAP system pressure does not remain constant, go to step 4.
32. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

1. Reviewing failure records vehicle mileage since diagnostic test last failed may help determine how often condition that caused DTC to set occurs. This may assist in diagnosing condition.
2. Use EVAP pressure/purge diagnostic station to pressurize EVAP system to aid in locating intermittent leaks. Move all EVAP components while testing with Ultrasonic Leak Detector.
3. A temporary blockage in EVAP canister purge valve, purge pipe or EVAP canister could cause an intermittent condition.

DTC P0442: EVAP CONTROL SYSTEM - SMALL LEAK DETECTED

Note. For circuit reference, see WIRING DIAGRAMS article.

EVAP small leak test applies vacuum to Evaporative Emission (EVAP) system and monitors vacuum decay. PCM monitors Fuel Tank Pressure (FTP) sensor signal to determine vacuum decay rate. At an appropriate time, PCM turns EVAP canister purge valve on (open) and EVAP vent valve on (closed). This allows engine to draw a vacuum on EVAP system. At a calibrated time, or vacuum level, PCM turns purge valve off (closed), sealing system, and monitors FTP sensor input in order to determine EVAP system vacuum decay. If system detects a leak larger than a calibrated amount DTC P0442 will set.

1. DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0452, or P0453 are not set.
2. Ignition voltage is 10-18 volts.
3. Barometric (BARO) pressure is more than 75 kPa.
4. Fuel level is 15-85 percent.
5. Engine Coolant Temperature (ECT) is 39-86°F (4-30°C).
6. Intake Air Temperature (IAT) is 39-86°F (4-30°C).
7. Start up ECT and IAT are within 16°F (9°C) of each other.
8. Vehicle Speed Sensor (VSS) is less than 75 MPH.

DTC sets when EVAP system can achieve vacuum, but a vacuum decay is detected during diagnostic test.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. If DTCs P0446, P0452, P0453, P0461, P0462, P0463 or P1441 are also set. see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If DTCs P0446, P0452, P0453, P0461, P0462, P0463 or P1441 are not set, go to next step.
3. Inspect EVAP system for the following conditions: Loose, missing, or damaged service port Schrader valve. Loose, incorrect, missing, or damaged fuel fill cap. Damaged EVAP canister purge valve. Raise vehicle on hoist. Inspect EVAP system for the following conditions: Disconnected, improperly routed, kinked, or damaged EVAP pipes and hoses. Damaged EVAP canister vent valve or EVAP canister. If problem was found, repair as necessary. After repairs, go to step 6 . If problem was not found, go to next step.
4. Always zero EVAP pressure and vacuum (in. H2O) gauges on EVAP pressure/purge diagnostic station before proceeding with diagnosis. Install fuel tank cap adapter. Connect EVAP pressure/purge diagnostic station and fuel tank cap to fuel tank cap adapter. Turn ignition on, engine off. Using scan tool, DTCs from PCM. Command EVAP vent valve on using scan tool. Pressurize EVAP system to 15 in. H2O with EVAP pressure/purge diagnostic station. Place control knob on EVAP pressure/purge diagnostic station to OFF/HOLD position. Monitor EVAP system pressure on EVAP pressure/purge diagnostic station for 5 minutes. If EVAP system pressure remains constant, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) . If EVAP system pressure does not remain constant, go to next step.
5. Using EVAP pressure/purge diagnostic station, continuously attempt to pressurize EVAP system. Using ultrasonic leak detector, inspect for leaks in the following locations: EVAP system purge pipe. EVAP vapor pipe. Canister/fuel tank. EVAP vent hose/pipe. Fuel fill pipe/hose and fuel fill cap. EVAP canister. EVAP canister vent valve. EVAP canister purge valve. Fuel sender assembly and/or seal. Fuel Tank Pressure (FTP) sensor seal. Fill limiter vent valve, pressure relief valve, rollover valves, and fuel tank. If problem was found, repair as necessary. After repairs, go to next step. If problem was not found, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
6. Turn ignition on, engine off. Command EVAP vent valve on using scan tool. Pressurize EVAP system to 15 in. H2O using EVAP pressure/purge diagnostic station. Place control knob on EVAP pressure/purge diagnostic station to OFF/HOLD position. Monitor EVAP system pressure on EVAP pressure/purge diagnostic station for 5 seconds. If EVAP system pressure remains constant, go to next step. If EVAP system pressure does not remain constant, go to step 2 .
7. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

EVAP system tests run when engine is first started and meets code enable criteria. To aid in locating intermittent leaks, use EVAP pressure/purge diagnostic station to pressurize EVAP system. Move all EVAP components while testing with ultrasonic leak detector.

DTC P0446: EVAP VENT SYSTEM PERFORMANCE

Note. For circuit reference, see WIRING DIAGRAMS article.

A restricted or blocked Evaporative Emission (EVAP) vent path is detected by PCM commanding purge valve on (open) and vent valve on (closed) allowing a vacuum to be applied to EVAP system. Once a calibrated vacuum level has been reached, PCM commands purge valve off (closed) and vent valve off (open) while monitoring Fuel Tank Pressure (FTP) sensor for a decrease in vacuum. If vacuum does not decrease to near zero in. H2O in a calibrated time, DTC P0446 will set.

1. DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0452, or P0453 are not set.
2. Ignition voltage is 10-18 volts.
3. Barometric (BARO) pressure is more than 75 kPa.
4. Fuel level is 15-85 percent.
5. Engine Coolant Temperature (ECT) is 39-86°F (4-30°C).
6. Intake Air Temperature (IAT) is 39-86°F (4-30°C).
7. Start up ECT and IAT are within 16°F (9°C) of each other.
8. Vehicle Speed Sensor (VSS) is less than 75 MPH.

DTC sets when fuel tank pressure is less than -10 in. H2O for as long as 30 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. If DTCs P0452 or P0453 also set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If DTCs P0452 or P0453 did not set, go to next step.
3. Inspect EVAP system for damaged EVAP vent valve or pinched EVAP vent hose. If problem was found, repair as necessary. After repairs, go to step 19 . If problem was not found, go to next step.
4. Install Fuel Tank Cap Adapter (J 41415-40) to fuel filler neck. Install EVAP Pressure/Purge Diagnostic Station (J 41413) and fuel tank cap to adapter. Turn ignition on, engine off. Command EVAP vent valve on (closed) using scan tool. Using EVAP pressure/purge diagnostic station, pressurize EVAP system to 13 in. H2O. Rotate EVAP pressure/purge diagnostic station rotary switch to OFF/HOLD position. Using scan tool, compare Fuel Tank Pressure (FTP) sensor value to EVAP pressure/purge diagnostic station gauge value. If EVAP pressure/purge diagnostic station gauge and scan tool FTP sensor values are similar, go to next step. If EVAP pressure/purge diagnostic station gauge and scan tool FTP sensor values are not similar, go to step 9 .
5. Monitor EVAP pressure/purge diagnostic station gauge. Command EVAP canister vent valve off (open). If EVAP pressure/purge diagnostic station gauge dropped quickly to near zero in. H2O, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) . If EVAP pressure/purge diagnostic station gauge did not drop quickly to near zero in. H2O, go to next step.
6. Command EVAP vent valve on and off using scan tool. EVAP vent valve is located near fuel tank under vehicle. If EVAP vent valve clicks when commanded on and off, go to next step. If EVAP vent valve does not click when commanded on and off, go to step 10 .
7. Turn ignition off. Reconnect all previously disconnected hardware. Using scan tool, command EVAP vent valve on. Using EVAP pressure/purge diagnostic station, pressurize EVAP system to 13 in. H2O. Rotate EVAP pressure/purge diagnostic station rotary switch to OFF/HOLD position. Disconnect EVAP vent hose from EVAP vent valve. If scan tool indicates fuel tank pressure near zero in. H2O, go to step 14 . If scan tool does not indicate fuel tank pressure near zero in. H2O, go to next step.
8. Disconnect EVAP vent hose from EVAP canister. If scan tool indicates fuel tank pressure near zero in. H2O, go to step 16 . If scan tool does not indicate fuel tank pressure near zero in. H2O, go to step 15 .
9. If FTP sensor value is more than 4.3 volts, see «DTC P0453: FUEL TANK PRESSURE SENSOR CIRCUIT - HIGH VOLTAGE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__dtc-p0453-fuel-tank-pressure-sensor) . If FTP sensor value is not more than 4.3 volts, go to step 12 .
10. Disconnect EVAP vent valve harness connector. Using test light connected to battery voltage, probe EVAP vent valve connector terminal "B" (White wire). If test light is on, go to next step. If test light is off, go to step 14 .
11. Check White wire between EVAP vent valve and PCM for short to ground. If problem was found, repair as necessary. After repairs, go to step 19 . If problem was not found, go to step 13 .
12. Check Fuel Tank Pressure (FTP) sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 19 . If problem was not found, go to step 17 .
13. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 19 . If problem was not found, go to step 18 .
14. Replace EVAP vent valve. After repairs, go to step 19 .
15. Replace EVAP canister. After repairs, go to step 19 .
16. Repair blockage in EVAP vent hose. After repairs, go to step 19 .
17. Replace FTP sensor. After repairs, go to step 19 .
18. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 19 .
19. Reconnect all EVAP hardware that was previously disconnected. Turn ignition on, engine off. Command EVAP canister vent valve on (closed) using scan tool. Using EVAP pressure/purge diagnostic station, pressurize EVAP system to 13 in. H2O. Rotate EVAP pressure/purge diagnostic station rotary switch to OFF/HOLD position. Command EVAP canister vent valve off (open). If EVAP pressure/purge diagnostic station value is near zero in. H2O, go to next step. If EVAP pressure/purge diagnostic station value is not near zero in. H2O, go to step 3 .
20. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

EVAP system runs test when engine is first started and meets code enable criteria. An intermittent condition could be caused by a damaged EVAP vent housing, a temporary blockage at EVAP vent valve inlet or a pinched vent hose. A blockage in vent system will also cause a poor fuel fill problem.

DTC P0452: FUEL TANK PRESSURE SENSOR CIRCUIT - LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM monitors Fuel Tank Pressure (FTP) sensor signal to detect vacuum decay and excess vacuum during enhanced Evaporative Emission (EVAP) diagnostic. PCM supplies a 5-volt reference and ground to sensor. FTP sensor signal voltage increases as fuel tank pressure decreases (negative pressure or vacuum, high voltage). FTP sensor signal voltage decreases as fuel tank pressure increases (positive pressure, low voltage). When FTP sensor signal is less than a predetermined value, DTC P0452 will set.

1. Ignition is on.

DTC sets when FTP sensor voltage is less than 0.1 volt for more than 5 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, observe FTP sensor voltage. If scan tool indicates FTP sensor voltage is less than 0.1 volt, go to step 4. If scan tool does not indicate FTP sensor voltage is less than 0.1 volt, go to next step.
3. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria, or as close to FREEZE FRAME/FAILURE RECORDS data that you observed. If DTC failed this ignition cycle, go to next step. If DTC did not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Raise vehicle. Disconnect fuel tank wiring harness at body pass-through connector. Pass-through connector is located near right front corner of fuel tank. Connect fused jumper wire (3-amp) between body pass-through connector terminals No. 3F (Gray wire) and No. 3G (Dark Green wire). (Scheme 13) Turn ignition on, engine off. Using scan tool, observe FTP sensor voltage. If scan tool indicates FTP sensor voltage is near 5 volts, go to step 7. If scan tool does not indicate FTP sensor voltage is not near 5 volts, go to next step.
5. Check Gray wire between FTP sensor and body pass-through connector for short to ground, or open between body pass-through connector and PCM. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to next step.
6. Check Dark Green wire between FTP sensor and pass-through connector for short to ground, or open between body pass-through connector and PCM. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 9.
7. Remove fuel tank. Disconnect FTP sensor harness connector. Check fuel tank wiring harness for pinches, cuts, or internal breaks. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to next step.
8. Check FTP sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 10.
9. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 11.
10. Replace FTP sensor. After repairs, go to step 12.
11. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 12.
12. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If DTC runs and passes, go to next step.
13. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

An intermittent open in the signal or 5-volt reference circuit or connectors will set DTC. Wiggle harnesses and connectors while monitoring tank pressure voltage. Review malfunction history data and attempt to reproduce condition and fault.

Scheme 13

DTC P0453: FUEL TANK PRESSURE SENSOR CIRCUIT - HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article.

Powertrain Control Module (PCM) monitors the Fuel Tank Pressure (FTP) sensor signal in order to detect vacuum decay and excess vacuum during the enhanced evaporative emission (EVAP) diagnostic. The PCM supplies a 5-volt reference and ground to the sensor. The FTP sensor signal voltage increases as the fuel tank pressure decreases (negative pressure or vacuum, high voltage). The FTP sensor signal voltage decreases as the fuel tank pressure increases (positive pressure, low voltage). When FTP sensor signal voltage is more than a predetermined value, DTC P0453 will set.

1. Ignition is on.

Fuel tank pressure sensor voltage is more than 4.9 volts. All conditions present for more than 5.0 seconds

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on, engine off. Using scan tool, observe FTP sensor voltage. If FTP sensor voltage more than 4.3 volts, go to step 4. If FTP voltage is not more than 4.3 volts, go to next step.
3. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or as close to FREEZE FRAME/FAILURE RECORDS data that you observed. If DTC failed this ignition cycle, go to next step. If DTC did not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Raise vehicle. Disconnect fuel tank wiring harness at body pass-through connector. Pass-through connector is located near right front corner of fuel tank. Turn ignition on, engine off. Using scan tool, observe FTP sensor voltage. If scan tool indicates FTP sensor voltage is more than zero volts, go to next step. If scan tool does not indicate FTP sensor voltage is more than zero volts, go to step 6.
5. Check Dark Green wire between body pass-through connector and PCM for short to voltage. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 9.
6. Using test light connected to battery voltage, probe body pass-through connector terminal 3H (Black wire). (Scheme 13) If test light is on, go to step 8. If test light is off, go to next step.
7. Check Black wire between body pass-through connector and PCM for open. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 9.
8. Remove fuel tank. Disconnect FTP sensor harness connector. Inspect fuel tank wiring harness for damaged wiring, poor connections and broken wires inside insulation. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 10.
9. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 11.
10. Replace FTP sensor. After repairs, go to step 12.
11. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 12.
12. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If DTC runs and passes, go to next step.
13. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

Check for damaged harness or poor connection at PCM or fuel tank pressure sensor.

DTC P0461: FUEL LEVEL SENSOR CIRCUIT PERFORMANCE

Note. For circuit reference, see WIRING DIAGRAMS article.

Fuel level sender changes resistance based on fuel level. PCM monitors signal circuit of fuel level sender in order to determine fuel level. When fuel tank is full, sender resistance is high and PCM senses a high signal voltage. When fuel tank is empty, sender resistance is low and PCM senses a low signal voltage. PCM uses signal circuit of fuel level sender in order to calculate total remaining fuel in tank. PCM sends fuel level percent via class 2 serial data circuit to instrument cluster in order to control fuel gauge. Fuel level information is also used for misfire and EVAP diagnostics.

1. Ignition is on.

DTC sets when fuel level input has not changed more than 1.6 percent in 120 miles.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Remove fuel level sender. Inspect for stuck fuel level sender (i.e. fuel strainer interfering with sender float arm) and foreign material in fuel tank (ice). If problem was found, repair as necessary. After repairs, go to step 4 . If problem was not found, go to next step.
3. Replace fuel level sender. After repairs, go to next step.
4. Using scan tool, clear DTCs. Operate vehicle within code enable criteria. If DTC does not reset, system is okay.

Use Freeze Frame and/or Failure Records data in order to locate an intermittent condition. If you cannot duplicate DTC, information included in Freeze Frame and/or Failure Records data may aid in determining number of miles since DTC set. Fail Counter and Pass Counter can also aid in determining number of ignition cycles that diagnostic reported a pass and/or fail. Operate vehicle within same freeze frame conditions (RPM, engine load, vehicle speed, temperature, etc.). This will isolate when DTC failed.

DTC P0462: FUEL LEVEL SENSOR CIRCUIT - LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article.

Fuel level sensor changes resistance based on fuel level. PCM monitors signal circuit of fuel level sensor in order to determine fuel level. When fuel tank is full, sensor resistance is high and PCM senses a high signal voltage. When fuel tank is empty, sensor resistance is low and PCM senses a low signal voltage. PCM uses signal circuit of fuel level sensor in order to calculate total remaining fuel in tank. PCM sends fuel level volume via class 2 serial data circuit to instrument cluster in order to control fuel gauge. Fuel level information is also used for misfire and EVAP diagnostics.

1. Ignition is on and system voltage is 11-16 volts.

DTC will set when fuel level sensor is less than 3.5 percent for more than 25 seconds on "J" body or less than 4 percent for more than 20 seconds on "N" body.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Using scan tool, observe FUEL LEVEL SENSOR parameter in PCM EVAP data list. If scan tool indicates FUEL LEVEL SENSOR parameter is less than 3.5 percent on "J" body or 2 percent on "N" body, go to next step. If scan tool does not indicate FUEL LEVEL SENSOR parameter is less than 3.5 percent on "J" body or 2 percent on "N" body, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
3. Turn ignition off. Disconnect fuel tank wiring harness at body pass-through connector. Pass-through connector is located near right front corner of fuel tank. Turn ignition on, engine off. Using scan tool, observe FUEL LEVEL SENSOR parameter. If scan tool indicates FUEL LEVEL SENSOR parameter is more than 98 percent on "J" body or 100 percent on "N" body, go to step 5 . If scan tool does not indicate FUEL LEVEL SENSOR parameter is more than 98 percent on "J" body or 100 percent on "N" body, go to next step.
4. Check Purple wire between body pass-through connector and PCM for short to ground. If problem was found, repair as necessary. After repairs, go to step 10 . If problem not found, go to step 7 .
5. Check Purple wire between body pass-through connector and fuel level sensor for short to ground. If problem was found, repair as necessary. After repairs, go to step 10 . If problem not found, go to next step.
6. Check fuel level sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 10 . If problem not found, go to step 8 .
7. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 10 . If problem not found, go to step 9 .
8. Replace fuel level sensor. After repairs, go to step 10 .
9. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
10. Using scan tool, clear DTCs. Operate vehicle within code enable criteria. If DTC does not reset, system is okay.

Use Freeze Frame and/or Failure Records data in order to locate an intermittent condition. If you cannot duplicate DTC, information included in Freeze Frame and/or Failure Records data may aid in determining number of miles since DTC set. Fail Counter and Pass Counter can also aid in determining number of ignition cycles that diagnostic reported a pass and/or fail. Operate vehicle within same freeze frame conditions (RPM, engine load, vehicle speed, temperature, etc.). This will isolate when DTC failed.

DTC P0463: FUEL LEVEL SENSOR CIRCUIT - HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article.

Fuel level sensor changes resistance based on fuel level. PCM monitors signal circuit of fuel level sensor in order to determine fuel level. When fuel tank is full, sensor resistance is high and PCM senses a high signal voltage. When fuel tank is empty, sensor resistance is low and PCM senses a low signal voltage. PCM uses signal circuit of fuel level sensor in order to calculate total remaining fuel in tank. PCM sends fuel level volume via class 2 serial data circuit to instrument cluster in order to control fuel gauge. Fuel level information is also used for misfire and EVAP diagnostics.

1. Ignition is on and system voltage is 11-16 volts.

On "J" body, DTC sets when fuel level sensor is more than 98 percent for more than 25 seconds.

On "N" body, DTC sets when fuel level sensor voltage is more than 3 volts or more than 100 percent for more than 20 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Using scan tool, observe FUEL LEVEL SENSOR parameter in PCM EVAP data list. If scan tool indicates FUEL LEVEL parameter is more than 98 percent on "J" body or 100 percent on "N" body, go to next step. If scan tool does not indicate FUEL LEVEL parameter is more than 98 percent on "J" body or 100 percent on "N" body, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
3. Turn ignition off. Disconnect fuel tank wiring harness at body pass-through connector. Pass-through connector is located near right front corner of fuel tank. Connect fused jumper wire (3-amp) between body pass-through connector terminals No. 3D (Purple wire) and No. 3H (Black wire). (Scheme 13) Turn ignition on, engine off. Using scan tool, observe FUEL LEVEL SENSOR parameter. If scan tool indicates FUEL LEVEL SENSOR parameter is less than 3.5 percent on "J" body or 2 percent on "N" body, go to step 6. If scan tool does not indicate FUEL LEVEL SENSOR parameter is less than 3.5 percent on "J" body or 2 percent on "N" body, go to next step.
4. Check Purple wire between body pass-through connector and PCM for open, high resistance or short to voltage. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to next step.
5. Check Black wire between pass-through connector and PCM for open or high resistance. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 9.
6. Check Purple wire between body pass-through connector and fuel level sensor for open, high resistance or short to voltage. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to next step.
7. Check Orange/Black wire between body pass-through connector and fuel level sensor for open or high resistance. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to next step.
8. Check fuel level sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 10.
9. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 12. If problem was not found, go to step 11.
10. Replace fuel level sensor. After repairs, go to step 12.
11. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
12. Using scan tool, clear DTCs. Operate vehicle within code enable criteria. If DTC does not reset, system is okay.

Use Freeze Frame and/or Failure Records data in order to locate an intermittent condition. If you cannot duplicate DTC, information included in Freeze Frame and/or Failure Records data may aid in determining number of miles since DTC set. Fail Counter and Pass Counter can also aid in determining number of ignition cycles that diagnostic reported a pass and/or fail. Operate vehicle within same freeze frame conditions (RPM, load, vehicle speed, temperature, etc.). This will isolate when the DTC failed.

DTC P0480: COOLING FAN RELAY NO. 1 CIRCUIT ("J" BODY)

Note. For circuit reference, see WIRING DIAGRAMS under ELECTRIC COOLING FANS - CARS article in ENGINE COOLING.

Battery voltage is supplied to cooling fan relay from cooling fan fuse. PCM controls cooling fan relay by grounding cooling fan relay control circuit via an internal solid state device called a driver. Primary function of driver is to supply ground for component being controlled. Each driver has a fault line which is monitored by PCM. When PCM is commanding a component on, voltage potential of control circuit should be low (near zero volts). When PCM is commanding control circuit to a component off, voltage potential of circuit should be high (near battery voltage). If fault detection circuit senses a voltage other than what is expected, the DTC will set.

PCM will monitor control circuit for the following

1. Short to ground.
2. Short to voltage.
3. Open circuit.
4. Open relay coil.
5. Internally shorted or excessively low resistance relay coil.

When PCM detects any of specified conditions, DTC will set and affected driver will be disabled.

1. Ignition is on.
2. System voltage is 9-18 volts.

An improper voltage level has been detected on cooling fan relay control circuit. Specified conditions are present for at least 30 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Using scan tool, command FC relay on and off. If cooling fan relay turns on and off with each command, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) . If cooling fan does not turn on and off with each command, go to next step.
3. Turn ignition off. Disconnect cooling fan relay. Cooling fan relay is located in underhood fuse block. Turn ignition on, engine off. Using test light connected to ground, probe battery voltage circuit (Red wire) of cooling fan relay connector. If test light is on, go to next step. If test light is off, go to step 10 .
4. Connect test light between control circuit (Dark Green wire) of cooling fan relay and battery voltage circuit (Red wire) of cooling fan relay. Using scan tool, command FC relay on and off. If test light turns on and off with each command, go to step 8 . If relay does not turn on and off with each command, go to next step.
5. If test light remains on with each command, go to step 7 . If test light does not remain on with each command, go to next step.
6. Check cooling fan relay control circuit (Dark Green wire) for short to voltage or open. If problem was found, repair as necessary. After repairs, go to step 14 . If problem was not found, go to step 9 .
7. Check cooling fan relay control circuit (Dark Green wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 14 . If problem was not found, go to step 9 .
8. Check cooling fan relay battery voltage circuit (Red wire) for short to ground or open. If problem was found, repair as necessary. After repairs, go to step 14 . If problem was not found, go to step 11 .
9. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 14 . If problem was not found, go to step 13 .
10. Check cooling fan relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 14 . If problem was not found, go to step 12 .
11. Repair short to ground in cooling fan motor supply voltage circuit (Red wire). After repairs, go to step 14 .
12. Replace cooling fan relay. After repairs, go to step 14 .
13. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
14. Using scan tool, clear DTCs. Operate vehicle within code enable criteria. If DTC does not reset, system is okay.

Review Freeze/Failure Records vehicle mileage since diagnostic test last failed. This may help determine how often condition that caused DTC to be set occurs.

DTC P0480: COOLING FAN RELAY NO. 1 CONTROL CIRCUIT ("N" BODY)

Note. For circuit reference, see WIRING DIAGRAMS under ELECTRIC COOLING FANS - CARS article in ENGINE COOLING.

Battery voltage is supplied to cooling fan 1 relay from cool fan 1 fuse. PCM controls cooling fan 1 relay by grounding low speed cooling fan relay control circuit via an internal solid state device called a driver. Primary function of driver is to supply ground for component being controlled. Each driver has a fault line which is monitored by PCM. When PCM is commanding a component on, voltage potential of control circuit should be low (near zero volts). When PCM is commanding control circuit to a component off, voltage potential of circuit should be high (near battery voltage). If fault detection circuit senses a voltage other than what is expected, DTC will set.

PCM will monitor control circuit for the following

1. Short to ground.
2. Short to voltage.
3. Open circuit.
4. Open relay coil.
5. An internally shorted or excessively low resistance relay coil.

When PCM detects any of specified conditions, DTC will set and affected driver will be disabled.

1. Ignition voltage is 9-18 volts.
2. Engine speed is more than 80 RPM.
3. PCM driver transitions from on to off or from off to on.

DTC sets when an improper voltage level has been detected on low speed cooling fan relay control circuit for at least 30 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Using scan tool, command FANS LOW SPEED on and off. If cooling fan 1 relay turns on and off with each command, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) . If cooling fan relay 1 does not turn on and off with each command, go to next step.
3. Turn ignition off. Disconnect cooling fan 1 relay. Cooling fan relays are located in underhood fuse block. Turn ignition on, engine off. Using test light connected to ground, probe battery voltage circuit of cooling fan 1 relay. If test light is on, go to next step. If test light is off, go to step 8 .
4. Connect test light between control circuit (Dark Green wire) of cooling fan 1 relay and battery voltage circuit of cooling fan 1 relay. Using scan tool, command FANS LOW SPEED on and off. If test light turns on and off with each command, go to step 10 . If test light does not turn on and off with each command, go to next step.
5. If test light remains on with each command, go to step 7 . If test light does not remain on with each command, go to next step.
6. Check control circuit (Dark Green wire) of cooling fan 1 relay for short to voltage or open. If problem was found, repair as necessary. After repairs, go to step 14 . If problem was not found, go to step 9 .
7. Check control circuit (Dark Green wire) of cooling fan 1 relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 14 . If problem was not found, go to step 9 .
8. Check battery voltage circuit of cooling fan 1 relay for short to ground or open. If problem was found, repair as necessary. After repairs, go to step 14 . If problem was not found, go to step 11 .
9. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 14 . If problem was not found, go to step 13 .
10. Check cooling fan 1 relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 14 . If problem was not found, go to step 12 .
11. Repair short to ground in cooling fan motor supply voltage circuit. After repairs, go to step 14 .
12. Replace cooling fan 1 relay. After repairs, go to step 14 .
13. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
14. Using scan tool, clear DTCs. Operate vehicle within code enable criteria. If DTC does not reset, system is okay.

Inspect for the following conditions

1. A faulty connection at PCM, inspect harness connectors for the following conditions: Backed out terminals. Improper mating. Broken locks. Improperly formed or damaged terminals. Faulty terminal-to-wire connections.
2. Inspect wiring harness for damage.
3. If harness appears to be okay, disconnect PCM, turn ignition on and observe DVOM connected between low speed cooling fan relay control circuit of cooling fan 1 relay and ground at PCM harness connector. While moving connectors and wiring harness related to cooling fan 1 relay, a change in voltage will indicate location of the fault.

Review Freeze/Failure Records vehicle mileage since diagnostic test last failed. This may help determine how often condition that caused DTC to be set occurs.

DTC P0481: COOLING FAN RELAY NO. 2 CONTROL CIRCUIT (2.4L "N" BODY)

Note. For circuit reference, see WIRING DIAGRAMS under ELECTRIC COOLING FANS - CARS article in ENGINE COOLING.

Battery voltage is supplied to cooling fan Series/Parallel (S/P) relay and cooling fan 3 relay from cool fan 2 fuse. PCM controls relays by grounding high speed cooling fan relay control circuit via an internal solid state device called a driver. Primary function of driver is to supply ground for component being controlled. Each driver has a fault line which is monitored by PCM. When PCM is commanding a component on, voltage potential of control circuit should be low (near zero volts). When PCM is commanding control circuit to a component off, voltage potential of circuit should be high (near battery voltage). If fault detection circuit senses a voltage other than what is expected, DTC will set.

PCM will monitor control circuit for short to ground, short to voltage and open circuit.

When PCM detects any of above conditions, DTC will set and affected driver will be disabled.

1. Ignition voltage is 9.0-18.0 volts.
2. Engine speed is more than 80 RPM.
3. PCM driver transitions from on to off or from off to on.

DTC sets when an improper voltage level has been detected on high speed cooling fan relay control circuit for at least 30 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Using scan tool, command FANS HIGH SPEED on and off. If cooling fan S/P and cooling fan 3 relays turn on and off with each command, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) . If cooling fan S/P and cooling fan 3 relays turn on and off with each command, go to next step.
3. Turn ignition off. Disconnect cooling fan 3 relay. Cooling fan relays are located in underhood fuse block. Turn ignition on, engine off. Using test light connected to ground, probe battery voltage circuit of cooling fan 3 relay. If test light is on, go to next step. If test light is off, go to step 8 .
4. Connect test light between control circuit (Dark Blue wire) of cooling fan 3 relay and battery voltage circuit of cooling fan 3 relay. Using scan tool, command FANS HIGH SPEED on and off. If test light turns on and off with each command, go to step 9 . If test light does not turn on and off with each command, go to next step.
5. If test light remains on with each command, go to step 7 . If test light does not remain on with each command, go to next step.
6. Check control circuit (Dark Blue wire) of cooling fan S/P relay and cooling fan 3 relay for short to voltage or open. If problem was found, repair as necessary. After repairs, go to step 12 . If problem was not found, go to step 9 .
7. Check control circuit (Dark Blue wire) of cooling fan S/P relay and cooling fan 3 relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 12 . If problem was not found, go to step 9 .
8. Check battery voltage circuit of cooling fan S/P relay and cooling fan 3 relay for open or short to ground. If problem was found, repair as necessary. After repairs, go to step 12 . If problem was not found, go to step 10 .
9. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 12 . If problem was not found, go to step 11 .
10. Repair short to ground in cooling fan motor supply voltage circuit (Gray wire). After repairs, go to step 12 .
11. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
12. Using scan tool, clear DTCs. Operate vehicle within code enable criteria. If DTC does not reset, system is okay.

Check for the following conditions

1. A faulty connection at the PCM, inspect the harness connectors for the following conditions: Backed out terminals. Improper mating. Broken locks. Improperly formed or damaged terminals. Faulty terminal-to-wire connections.
2. Inspect wiring harness for damage.
3. If harness appears to be okay, disconnect PCM, turn ignition on and observe DVOM connected between high speed cooling fan relay control circuit and ground at PCM harness connector. While moving connectors and wiring harness related to cooling fan S/P and cooling fan 3 relays, a change in voltage will indicate location of the fault.

Review Freeze/Failure Records vehicle mileage since diagnostic test last failed. This may help determine how often condition that caused DTC to be set occurs.

DTC P0502: OUTPUT SPEED SENSOR CIRCUIT - LOW OUTPUT (A/T)

Note. Output Speed Sensor (OSS) is also referred to as Vehicle Speed Sensor (VSS).

Note. For circuit reference, see WIRING DIAGRAMS article.

Automatic Transmission Output (shaft) Speed Sensor (AT OSS) provides vehicle speed information to PCM. AT OSS is a permanent magnet generator mounted to the transmission case. AT OSS produces an AC voltage as transmission speed sensor rotor teeth pass through sensor's magnetic field. AC voltage level increases as speed of vehicle increases. PCM converts AC voltage into a digital signal. PCM uses the vehicle speed signal to determine shift timing, Torque Converter Clutch (TCC) apply, TCC release, and gear ratio calculations.

When PCM detects a low output speed and vehicle has a large engine speed in a drive gear, then DTC P0502 sets.

1. DTCs P0107, P0108, P0121, P0122, P0123, P0716, P0717 or DTC P1810 are not set.
2. Transmission is in a Drive.
3. TP angle is more than 12 percent.
4. MAP is more than 50 kPa.
5. Input speed is more than 2000 RPM.

DTC sets when output speed is less than 2 MPH for 3 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Record DTC FREEZE FRAME and FAILURE RECORDS. Clear DTC. Raise and support drive wheels. Start and idle engine. Place transmission in Drive. Select TRANSMISSION OSS on scan tool. With drive wheels rotating, if TRANSMISSION OSS increases when wheel speed increases, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l). With drive wheels rotating, if TRANSMISSION OSS does not increase when wheel speed increases, go to next step.
3. Turn ignition off. Disconnect PCM connectors C1 and C2. Using Connector Test Adapter Kit (J 35616-A), connect DVOM between PCM connector C1 terminal No. 64 (Purple wire) and connector C2 terminal No. 61 (Yellow wire). (Scheme 5) Select AC volts. Turn ignition on, engine off. Rotate right front drive wheel by hand. Observe DVOM display. If a voltage more than 0.5 volt AC can be obtained, go to step 14. If a voltage more than 0.5 volt AC cannot be obtained, go to next step.
4. Leave DVOM test leads connected. Measure circuit resistance. If resistance is 1530-1870 ohms, go to step 8. If resistance is not 1530-1870 ohms, go to next step.
5. If resistance is more than 1870 ohms, go to step 11. If resistance is not more than 1870 ohms, go to next step.
6. Leave DVOM test leads connected. Disconnect OSS connector at transmission. If resistance less than 1530 ohms, go to next step. If resistance is not less than 1530 ohms, go to step 13.
7. Repair short between Purple wire and Yellow wire of OSS. After repairs, go to step 15.
8. Check Yellow wire between OSS and PCM for short to ground. If problem was found, repair as necessary. After repairs, go to step 15. If problem was not found, go to next step.
9. Reconnect PCM connectors C1 and C2. Select DC volts on DVOM. Using connector test adapter kit, connect DVOM test leads to terminals "A" and "B" of OSS harness connector end. Turn ignition on, engine off. If DVOM displays system voltage, go to next step. If DVOM does not display system voltage, go to step 12.
10. Repair short to voltage in Yellow wire between OSS and PCM. After repairs, go to step 15.
11. Check Yellow wire and Purple wire between OSS and PCM for an open. If problem was found, repair as necessary. After repairs, go to step 15. If problem was not found, go to step 13.
12. Remove OSS. Inspect OSS and transmission for the following conditions: Incorrect OSS. OSS damage. Excessive OSS to speed sensor rotor gap. Incorrect speed sensor rotor alignment. Speed sensor rotor damage. Repair specified conditions as necessary. After repairs, go to step 15.
13. Replace OSS. After repairs, go to step 15.
14. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
15. Using scan tool, clear DTC. Operate vehicle at a speed more than 2 MPH for 3 seconds. If DTC does not reset, system is okay.

DTC can falsely set if engine is "brake torqued" in gear. Disregard DTC if set while drive wheels are not turning.

An intermittent problem can be caused by a poor connection, rubbed through wire insulation or broken wire inside insulation. Thoroughly check OSS circuits.

DTC P0502: VEHICLE SPEED SENSOR CIRCUIT - LOW OUTPUT (M/T)

Note. Output Speed Sensor (OSS) is also referred to as Vehicle Speed Sensor (VSS).

Note. For circuit reference, see WIRING DIAGRAMS article.

Vehicle speed information is provided to PCM by Vehicle Speed Sensor (VSS). VSS is a permanent magnet generator that is mounted in transaxle and produces a pulsing voltage whenever vehicle speed is over about 5 KM/H. AC voltage level and the number of pulses increases with vehicle speed. PCM converts pulsing voltage into MPH and then supplies necessary signal to instrument panel for speedometer, odometer operation and to cruise control module and multi-function alarm module operation.

1. DTCs P0107, P0108, P0122 or P0123 are not present.
2. Engine speed is 1700-3600 RPM.
3. Throttle Position (TP) is 0-1 percent.
4. Engine vacuum is 21-24 in. Hg.
5. Specified conditions are met for 5 seconds.

DTC sets when vehicle speed is less than 2 MPH.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Record DTC FREEZE FRAME and FAILURE RECORDS. Clear DTC. Raise drive wheels. Support lower control arms so drive axles are in a horizontal (straight) position. Start engine. Allow engine to idle in gear. If scan tool displays vehicle speed more than zero MPH, go to next step. If scan tool does not display vehicle speed more than zero MPH, go to step 4.
3. Turn ignition off. Turn ignition on, engine off. Review FREEZE FRAME data and note parameters. Start engine. Operate vehicle within FREEZE FRAME conditions and code enable criteria. If scan tool displays vehicle speed more than zero MPH, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l). If scan tool does not display vehicle speed more than zero MPH, go to next step.
4. Verify latest calibration is installed in PCM. Update PCM with latest calibration as necessary. If PCM required a calibration update, go to step 14. If PCM did not require a calibration update, go to next step.
5. Turn ignition off. Disconnect PCM. Measure resistance between PCM connector C1 terminal No. 64 and connector C2 terminal No. 61 (Yellow wire). (Scheme 5) If resistance is 530-870 ohms, go to step 7. If resistance is not 530-870 ohms, go to next step.
6. Check Yellow wire and Purple wire between VSS and PCM for open circuit, and for Yellow wire and Purple wire shorted together. If problem was found, repair as necessary. After repairs, go to step 14. If problem was not found, go to step 11.
7. Measure resistance between PCM connector C1 terminal No. 64 and ground. If resistance is more than 50 k/ohms, go to step 10. If resistance is not more than 50 k/ohms, go to next step.
8. Leave DVOM connected between terminal No. 64 and ground. Disconnect VSS. Measure resistance between PCM connector C1 terminal No. 64 and ground. If resistance is more than 50 k/ohms, go to step 11. If resistance is not more than 50 k/ohms, go to next step.
9. Repair short to ground in Yellow wire between VSS and PCM. After repairs, go to step 14.
10. Connect DVOM between PCM connector C1 terminal No. 64 and connector C2 terminal No. 61. Measure AC voltage with DVOM while rotating drive wheels by hand. If AC voltage is equal to or more than 0.5 volt, go to step 14. If AC voltage is not equal to or more than 0.5 volt, go to next step.
11. Remove VSS. Inspect VSS and VSS rotor for following conditions: VSS damage. VSS rotor damage. Excessive air gap between VSS rotor and VSS. Incorrect alignment between VSS and VSS rotor. If problem was found, repair as necessary. After repairs. go to step 14. If problem was not found, go to next step.
12. Replace VSS. After repairs, go to step 14.
13. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
14. Using scan tool, clear DTCs. Start engine. Idle at normal operating temperature. Operate vehicle within code enable criteria. If DTC does not reset, system is okay.

Ensure VSS is correctly torqued to transmission housing.

An intermittent problem can be caused by a poor connection, rubbed through wire insulation or broken wire inside insulation. Thoroughly check OSS circuits.

DTC P0503: VEHICLE SPEED SENSOR CIRCUIT - DROP IN OUTPUT (A/T)

Note. Output Speed Sensor (OSS) is also referred to as Vehicle Speed Sensor (VSS).

Note. For circuit reference, see WIRING DIAGRAMS article.

Automatic Transmission Output (shaft) Speed Sensor (AT OSS) provides vehicle speed information to PCM. AT OSS is a permanent magnet generator mounted to transmission case. AT OSS produces an AC voltage as transmission speed sensor rotor teeth pass through sensor's magnetic field. AC voltage level increases as speed of vehicle increases. PCM converts AC voltage into a digital signal. PCM uses vehicle speed signal to determine shift timing, Torque Converter Clutch (TCC) apply, TCC release, and gear ratio calculations.

When PCM detects a loss of vehicle speed while vehicle is in motion, then DTC P0503 sets.

1. DTC P1810 must not be set.
2. Engine run time is more than 5 seconds.
3. Time since gear select lever change is more than 6 seconds.
4. An increase in output speed of 500 RPM or more has not occurred for more than 5 seconds.

DTC sets when output speed drops more than 1200 RPM for 3 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Record DTC FREEZE FRAME and FAILURE RECORDS. Clear DTC. Raise and support drive wheels. Start and idle engine. Place transmission in Drive. Select TRANSMISSION OSS on scan tool. With drive wheels rotating, if TRANSMISSION OSS increases when wheel speed increases, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l). With drive wheels rotating, if TRANSMISSION OSS does not increase when wheel speed increases, go to next step.
3. Turn ignition off. Disconnect PCM connectors C1 and C2. Using Connector Test Adapter Kit (J 35616-A), connect DVOM between PCM connector C2 terminal No. 64 and connector C2 terminal No. 61. (Scheme 5) Select AC volts on DVOM. Turn ignition on, engine off. Rotate right front drive wheel by hand. Observe DVOM display. If a voltage more than 0.5 volt AC can be obtained, go to step 14. If a voltage more than 0.5 volt AC cannot be obtained, go to next step.
4. Leave DVOM test leads connected. Measure circuit resistance. If circuit resistance is 1530-1870 ohms, go to step 8. If circuit resistance is not 1530-1870 ohms, go to next step.
5. If circuit resistance is more than 1870 ohms, go to step 11. If circuit resistance is not more than 1870 ohms, go to next step.
6. Leave DVOM test leads connected. Disconnect OSS connector at transmission. If circuit resistance is less than 1530 ohms, go to next step. If circuit resistance is not less than 1530 ohms, go to step 13.
7. Repair short between Yellow wire and Purple wire between OSS and PCM. After repairs, go to step 15.
8. Check Yellow wire for short to ground. If problem was found, repair as necessary. After repairs, go to step 15. If problem was not found, go to next step.
9. Reconnect PCM connectors C1 and C2. Select DC volts. Using connector test adapter kit, connect DVOM test leads to terminals "A" and "B" of OSS harness connector. Turn ignition on, engine off. If DVOM displays system voltage, go to next step. If DVOM does not display system voltage, go to step 12.
10. Repair short to voltage in Yellow wire between OSS and PCM. After repairs, go to step 15.
11. Check Yellow wire between OSS and PCM for an open. Check Purple wire between OSS and PCM for an open. If problem was found, repair as necessary. After repairs, go to step 15. If problem was not found, go to step 13.
12. Remove OSS. Check OSS and transmission for the following conditions: Incorrect OSS. OSS damage. Excessive OSS to speed sensor rotor gap. Incorrect speed sensor rotor alignment. Speed sensor rotor damage. Repair specified conditions as necessary. After repairs, go to step 15.
13. Replace OSS. After repairs, go to step 15.
14. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
15. Using scan tool, clear DTCs. Operate vehicle within code enable criteria. If DTC does not reset, system is okay.

An intermittent problem can be caused by a poor connection, rubbed through wire insulation or broken wire inside insulation. Thoroughly check OSS circuits.

DTC P0506: IDLE SPEED LOW

Note. For circuit reference, see WIRING DIAGRAMS article.

Idle Air Control (IAC) valve is located in throttle body. valve consists of a movable pintle, driven by a gear attached to an electric motor called a stepper motor. IAC valve motor is a 2-phase bi-polar permanent magnet stepper motor that is capable of highly accurate rotation, or movement, every time polarity of a winding is changed. This change in polarity can be seen when observing a test light connected between ground or battery voltage and an IAC valve circuit while PCM is attempting to change engine RPM. Test light will flash on or off each time polarity is changed. PCM does not use a physical sensor to determine IAC pintle position, but uses a predicted number of counts, one count represents one change in polarity which equals one step of stepper motor. PCM counts steps it has commanded to determine IAC pintle position. PCM uses IAC valve to control engine idle speed. It does this by changing pintle position in idle air passage of throttle body. This varies airflow around throttle plate when throttle is closed. To determine desired position of IAC pintle at idle or during deceleration, PCM refers to following inputs

1. Engine RPM.
2. Battery voltage.
3. Air temperature.
4. Engine coolant temperature.
5. Throttle position sensor angle.
6. Engine load.
7. Vehicle speed.

When ignition key is turned off after an ignition cycle, PCM will first seat IAC pintle in air by-pass bore, and then retract it a predetermined amount of counts to allow proper amount of air to by-pass throttle plate for engine start-up. This procedure is known as an IAC Reset.

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0128, P0130, P0131, P0132, P0133, P0134, P0171, P0172, P0201-P0204, P0300, P0301-P0304, P0336, P0440, P0442, P0446, P0452, P0453, P0502, P0503, P1133, or P1441 are not set.
2. ECT is more than 104°F (40°C).
3. BARO is more than 72 kPa.
4. Engine run time is more than 20 seconds.
5. Ignition voltage is more than 11.3 volts.

DTC sets when

1. Actual engine speed is 100 RPM less than desired engine speed for 19 seconds for M/T.
2. Actual engine speed is 60 RPM less than desired engine speed for 13 seconds for A/T.
3. IAC command is more than 145 counts.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Set parking brake and block drive wheels. Install scan tool. Start engine. Turn off all accessories. Use scan tool RPM control function to slowly increment engine speed to 1800 RPM, then to 600 RPM, then to 1800 RPM. Exit RPM control function. If engine speed stabilized within 60 RPM for A/T or within 100 RPM for M/T of commanded RPM, go to next step. If engine speed does not stabilize within 60 RPM for A/T or within 100 RPM for M/T of commanded RPM, go to step 4.
3. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or as close to FREEZE FRAME/FAILURE RECORDS data that you observed. If DTC fails this ignition cycle, go to next step. If DTC does not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Disconnect IAC valve harness connector. (Scheme 6)or (Scheme 7). Connect IAC Motor Driver (J 37027-A) to IAC valve. Start engine. Use IAC motor driver to command IAC valve in until 600 RPM is reached. Use IAC motor driver to command IAC valve out until 1800 RPM is reached. Return engine speed to desired idle as indicated on scan tool data list. If engine speed steadily decreased to 600 RPM and steadily increased to 1800 RPM when IAC valve was commanded in and out, go to next step. If engine speed did not steadily decrease to 600 RPM and steadily increase to 1800 RPM when IAC valve was commanded in and out, go to step 11.
5. Using test light connected to ground, probe one of IAC valve circuits at IAC valve harness connector using Connector Test Adapter Kit (J 35616-A). Start engine. Use IAC motor driver to command low RPM while observing a scan tool until IAC counts start to increment. Using IAC motor driver, command high RPM while observing a scan tool until IAC counts start to increment. While IAC counts are incrementing, observe test light. Return engine to desired idle speed as indicated on scan tool data list. Repeat procedure for other 3 IAC valve circuits. If test light remained on (never flashing) while IAC counts were incrementing at any of the IAC valve circuits, go to step 10. If test light did not remain on (never flashing) while IAC counts were incrementing at any of the IAC valve circuits, go to next step.
6. If test light remained off (never flashing) while IAC counts were incrementing at any of the IAC valve circuits, go to step 9. If test light did not remain off (never flashing) while IAC counts were incrementing at any of the IAC valve circuits, go to next step.
7. Connect test light between IAC connector terminals "C" (Light Blue/Black wire) and "D" (Light Blue/White) at IAC valve harness connector using connector test adapter kit. (Scheme 14) Use IAC motor driver to command low RPM while observing scan tool until IAC counts start to increment. With IAC motor driver, command high RPM while observing scan tool until IAC counts start to increment. While IAC counts are incrementing, observe test light. Return engine to desired idle speed as indicated on scan tool data list. Repeat procedure with test light connected between IAC connector terminals "A" (Light Green/Black wire) and "B" (Light Green/White wire) at IAC valve harness connector. Return engine to desired idle speed as indicated on scan tool data list. If test light remained on (never flashing) while IAC counts were incrementing, go to next step. If test light did not remain on (never flashing) while IAC counts were incrementing, go to step 15.
8. Check IAC valve harness connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
9. Turn ignition off. Disconnect PCM harness connectors. Using DVOM, test for open or short ground on IAC valve circuit where test light remained off. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 12.
10. Turn ignition on. Using DVOM, test for short to voltage on IAC valve circuit where test light remained illuminated. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 12.
11. Visually/Physically inspect for the following: Throttle body damage and tampering. Throttle lever screw tampering (if equipped). Restricted air intake system. Inspect for a possible collapsed or clogged air intake duct before and after air filter element, restricted air filter element, or restriction at throttle body intake screen, if equipped. Remove IAC valve. Inspect for the following: A clogged IAC passage Excessive deposits on throttle plate. Excessive deposits in throttle bore. Excessive deposits on IAC valve pintle. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 13.
12. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 15.
13. Check IAC valve connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to next step.
14. Replace IAC valve. After repairs, go to step 16.
15. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
16. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If DTC does not reset, go to next step.
17. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

Inspect for the following conditions

1. Restricted air intake system.
2. Tampered with or damaged throttle stop screw.
3. Tampered with or damaged throttle plate, throttle shaft, or throttle linkage.
4. Objects blocking IAC passage or throttle bore.
5. Excessive deposits in IAC passage or on IAC pintle.
6. Excessive deposits in throttle bore or on throttle plate.
7. Vacuum leaks.
8. Low or unstable idle condition could be caused by non-IAC system problem that cannot be overcome by IAC valve.

Scheme 14

DTC P0507: IDLE SPEED HIGH

Note. For circuit reference, see WIRING DIAGRAMS article.

Idle Air Control (IAC) valve is located in throttle body. Valve consists of a movable pintle, driven by a gear attached to an electric motor called a stepper motor. IAC valve motor is a 2-phase bi-polar permanent magnet stepper motor that is capable of highly accurate rotation, or movement, every time polarity of a winding is changed. This change in polarity can be seen when observing a test light connected between ground or battery voltage and an IAC valve circuit while PCM is attempting to change engine RPM. Test light will flash on or off each time polarity is changed. PCM does not use a physical sensor to determine IAC pintle position, but uses a predicted number of counts, one count represents one change in polarity which equals one step of stepper motor. PCM counts steps it has commanded to determine IAC pintle position. PCM uses IAC valve to control engine idle speed. It does this by changing pintle position in idle air passage of throttle body. This varies airflow around throttle plate when throttle is closed. To determine desired position of IAC pintle at idle or during deceleration, PCM refers to following inputs

1. Engine RPM.
2. Battery voltage.
3. Air temperature.
4. Engine coolant temperature.
5. Throttle position sensor angle.
6. Engine load.
7. Vehicle speed.

When ignition key is turned off after an ignition cycle, PCM will first seat IAC pintle in air by-pass bore, and then retract it a predetermined amount of counts to allow proper amount of air to by-pass throttle plate for engine start-up. This procedure is known as an IAC Reset.

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0128, P0130, P0131, P0132, P0133, P0134, P0171, P0172, P0201-P0204, P0300, P0301-P0304, P0336, P0440, P0442, P0446, P0452, P0453, P0502, P0503, P1133, or P1441 are not set.
2. ECT is more than 104°F (40°C).
3. BARO is more than 72 kPa.
4. Engine run time is more than 20 seconds.
5. Ignition voltage more than 11.3 volts.

DTC sets when actual engine speed is 60 RPM more than desired engine speed for 13 seconds. IAC command is less than 2 counts.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Set parking brake and block drive wheels. Install scan tool. Start engine. Turn off all accessories. Use scan tool RPM control function in order to slowly increment engine speed to 1800 RPM, then to 600 RPM, then to 1800 RPM. Exit RPM control function. If engine speed stabilizes within 60 RPM of commanded RPM, go to next step. If engine speed does not stabilize within 60 RPM of commanded RPM, go to step 4.
3. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or close to FREEZE FRAME/FAILURE RECORDS data that you observed. If DTC failed this ignition cycle, go to next step. If DTC did not fail this ignition cycle, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Disconnect IAC valve harness connector. (Scheme 6)or (Scheme 7). Connect IAC Motor Driver (J 37027-A) to IAC valve. Start engine. Use IAC motor driver to command IAC valve in until 600 RPM is reached. Use IAC motor driver to command IAC valve out until 1800 RPM is reached. Return engine to desired idle speed as indicated on scan tool data list. If engine speed steadily decreased to 600 RPM and steadily increased to 1800 RPM when IAC valve was commanded in and out, go to next step. If engine speed did not steadily decrease to 600 RPM and steadily increase to 1800 RPM when IAC valve was commanded in and out, go to step 11.
5. Using test light connected to ground, probe one of IAC valve circuits at IAC valve harness connector using Connector Test Adapter Kit (J 35616-A). Start engine. Use IAC motor driver to command low RPM while observing a scan tool until IAC counts start to increment. Using IAC motor driver, command high RPM while observing a scan tool until IAC counts start to increment. While IAC counts are incrementing, observe test light. Return engine to desired idle speed as indicated on scan tool data list. Repeat procedure for other 3 IAC valve circuits. If test light remains on (never flashing) while IAC counts were incrementing at any of IAC valve circuits, go to step 10. If test light does not remain on (never flashing) while IAC counts were incrementing at any of IAC valve circuits, go to next step.
6. If test light remained off (never flashing) while IAC counts were incrementing at any of IAC valve circuits during above test, go to step 9. If test light did not remain off (never flashing) while IAC counts were incrementing at any of IAC valve circuits, go to next step.
7. Connect test light between IAC connector terminals "C" (Light Blue/Black wire) and "D" (Light Blue/White wire) at IAC valve harness connector using connector test adapter kit. (Scheme 14) Using IAC motor driver, command low RPM while observing scan tool until IAC counts start to increment. Using IAC motor driver, command high RPM while observing a scan tool until IAC counts start to increment. While IAC counts are incrementing, observe test light. Return engine to desired idle speed as indicated on scan tool data list. Repeat procedure with test light connected between IAC connector terminals "A" (Light Green/Black wire) and "B" (Light Green/White wire) at IAC valve harness connector. Return engine to desired idle speed as indicated on scan tool data list. If test light stayed on (never flashing) while IAC counts were incrementing, go to next step. If test light did not stay on (never flashing) while IAC counts were incrementing, go to step 15.
8. Check IAC valve connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
9. Turn ignition off. Disconnect PCM harness connectors. Using DVOM, test for open or short to ground in IAC valve circuit where test light remained off. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 12.
10. Turn ignition on. Using DVOM, test for short to voltage in IAC valve circuit where test light remained on. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 12.
11. Visually/Physically inspect for the following: Throttle body damage and tampering. Throttle lever screw tampering (if equipped). Vacuum leaks. Faulty, incorrectly installed PCV valve and hose (if equipped). Throttle shaft binding. Throttle linkage or cruise control linkage binding (if equipped). Remove IAC valve. Inspect for the following: Clogged IAC passage. Excessive deposits on throttle plate. Excessive deposits in throttle bore. Excessive deposits on IAC Valve pintle. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 13.
12. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 15.
13. Check IAC valve connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to next step.
14. Replace IAC valve. After repairs, go to step 16.
15. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
16. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If DTC does not reset, go to next step.
17. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

Inspect for the following conditions

1. Correct PCV valve, properly installed and properly operating.
2. Proper operation and installation of all air intake components.
3. Proper installation and operation of mass airflow sensor, if equipped.
4. Tampered with or damaged throttle stop screw.
5. Tampered with or damaged throttle plate, throttle shaft, throttle linkage, or cruise control linkage, if equipped.
6. Skewed high TP sensor.
7. Excessive deposits in IAC passage or on IAC pintle.
8. Excessive deposits in throttle bore or on throttle plate.
9. Vacuum leaks.
10. High or unstable idle condition, could be caused by a non-IAC system problem that cannot be overcome by IAC valve.

DTC P0562: SYSTEM VOLTAGE LOW

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM checks system voltage to make sure voltage stays within proper range. Damage to components, and incorrect input can occur when voltage is out of range. PCM monitors system voltage over an extended length of time. If PCM detects an excessively low system voltage, DTC P0562 will set.

1. Engine speed more than 1500 RPM.
2. System voltage 9.5-18.0 volts.

DTC sets when PCM detects a system voltage less than 10 volts for 5 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Using scan tool, observe IGNITION 1 SIGNAL parameter in PCM data list. If scan tool indicates IGNITION 1 SIGNAL parameter is more than 10.5 volts, go to step 6 . If scan tool does not indicate IGNITION 1 SIGNAL parameter is more than 10.5 volts, go to next step.
3. Measure voltage at battery and compare it with IGNITION 1 SIGNAL parameter in PCM data list. If battery voltage and PCM ignition 1 readings differ by more than 0.8 volt, go to next step. If battery voltage and PCM ignition 1 readings do not differ by more than 0.8 volt, see CHARGING SYSTEM TEST in appropriate GENERATORS & REGULATORS article.
4. Check Orange wire between underhood fuse block and PCM for high resistance. If problem was found, repair as necessary. After repairs, go to step 7 . If problem was not found, go to next step.
5. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 7 . If problem was not found, go to next step.
6. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
7. Record scan tool FAIL RECORDS data. Using scan tool, clear DTC(s). Operate vehicle within code enable criteria. Using scan tool, observe SPECIFIC DTC INFORMATION for DTC P0562 until test runs. If DTC does not reset, system is okay.

If DTC sets when an accessory is operated, check for poor connection or excessive current draw.

DTC P0563: SYSTEM VOLTAGE HIGH

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM checks system voltage to make sure voltage stays within proper range. Damage to components, and incorrect input can occur when voltage is out of range. PCM monitors system voltage over an extended length of time. If PCM detects an excessively high system voltage, DTC P0563 will set.

1. Engine speed more than 1500 RPM.
2. System voltage 9.5-18.0 volts.

DTC sets when PCM detects system voltage more than 16 volts for less than one second.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Using scan tool, observe IGNITION 1 SIGNAL parameter in PCM data list. If scan tool indicates IGNITION 1 SIGNAL parameter is less than 16.0 volts, go to step 4 . If scan tool does not indicate IGNITION 1 SIGNAL parameter is less than 16.0 volts, go to next step.
3. Measure voltage at battery and compare it with IGNITION 1 SIGNAL parameter in PCM data list. If battery voltage and PCM IGNITION 1 readings differ by more than 0.8 volt, go to next step. If battery voltage and PCM IGNITION 1 readings do not differ by more than 0.8 volt, see CHARGING SYSTEM TEST in appropriate GENERATORS & REGULATORS article.
4. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
5. Record scan tool FAIL RECORDS data. Using scan tool, clear DTC(s). Operate vehicle within code enable criteria. Using scan tool, observe SPECIFIC DTC INFORMATION for DTC P0562 until test runs. If DTC does not reset, system is okay.

If DTC sets when an accessory is operated, check for poor connection or excessive current draw.

DTC P0601-P0607, P1600, P1621, P1627, P1680 0R P1683: PCM MEMORY

Note. For circuit reference, see WIRING DIAGRAMS article.

This diagnostic test applies to internal microprocessor integrity conditions within control module. This diagnostic test also addresses if control module is not programmed.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. If DTC P0602 is set, go to next step. If DTC P0602 is not set, go to step 5 .
3. Program PCM. See «POWERTRAIN CONTROL MODULE REPROGRAMMING»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-control-module-reprogramming) under PROGRAMMING. If DTC P0602 resets, go to next step. If DTC P0602 resets, go to step 6 .
4. Ensure all tool connections are secure. Ensure programming equipment is operating correctly. Ensure correct software/calibration package is used. Attempt to program PCM. See «POWERTRAIN CONTROL MODULE REPROGRAMMING»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-control-module-reprogramming) under PROGRAMMING. If DTC P0602 resets, go to next step. If DTC P0602 does not reset, go to step 6 .
5. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
6. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle. If DTC does not reset, go to next step.
7. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

Alternate Fuel Engine Control Unit (AF ECU) contains data storage areas. AF ECU runs a test on stored data called check-sum. This DTC is used to indicate a failure has occurred within AF ECU.

For DTC to run, ignition must be on. DTC will set when AF ECU detects and internal malfunction.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to next step.
3. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM.

PCM uses generator turn on signal circuit to control load of generator on engine. A high side driver in PCM applies a voltage to voltage regulator. This signals voltage regulator to turn field circuit on and off. When PCM turns on high side driver, voltage regulator turns on field circuit. When PCM turns off high side driver, voltage regulator turns off field circuit.

PCM monitors state of generator turn on signal circuit. PCM should detect a low generator turn on signal circuit voltage when key is on and engine is off, or when charging system malfunctions. With engine running, PCM should detect a high generator turn on signal circuit. PCM performs KEY ON and RUN tests to determine status of generator turn on signal circuit. During KEY ON test, if PCM detects a high generator turn on signal circuit voltage, DTC P0621 will set. DTC P0621 will also set if, during RUN test, PCM detects a low generator turn on signal circuit. When DTC sets, PCM will send a class 2 serial data message to IPC to illuminate charge indicator.

1. Key On Test No generator, CKP sensors, or CMP sensor DTCs are set. Key is in RUN position. Engine is not running.
2. Run Test No generator, CKP sensors, or CMP sensor DTCs are set. Engine is running.

DTC sets when

1. Key On Test PCM detects a high signal voltage on generator turn on signal circuit for at least 5 seconds.
2. Run Test PCM detects a low signal voltage on generator turn on signal circuit for at least 15 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Start engine. Using scant tool, monitor DTC information for DTC P0621 in ENGINE CONTROLS. If scan tool indicate DTC P0621 passed, problem is intermittent. If scan tool does not indicate DTC P0621 passed, go to next step.
3. Check Red wire between generator and PCM for short or open. If problem was found, repair as necessary. After repairs, go to step 6 . If problem was not found, go to next step.
4. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 6 . If problem was not found, go to next step.
5. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
6. Record scan tool FAIL RECORDS data. Clear any DTCs. Operate vehicle within FAIL RECORDS conditions as noted. Using scan tool, monitor SPECIFIC DTC info for this DTC. If scan tool indicates DTC did not fail this ignition cycle, system is okay.

PCM uses generator field duty cycle signal circuit to monitor duty cycle of generator. Generator field duty cycle signal circuit connects to high side of field winding in generator. A pulse width modulated (PWM) high side driver in voltage regulator turns field winding on and off. PCM uses PWM signal input to determine generator load on engine. This allows PCM to adjust idle speed to compensate for high electrical loads.

PCM monitors state of generator field duty cycle signal circuit. When key is in RUN position and engine is off, PCM should detect a duty cycle near zero percent. However, when engine is running, duty cycle should be between 5 percent and 100 percent. PCM monitors PWM signal using a KEY ON test and a RUN test. During tests, if PCM detects an out of range PWM signal, DTC P0622 will set. When DTC sets, PCM will send a class 2 serial data message to IPC to illuminate charge indicator.

1. Key On Test No generator, CKP sensor, or CMP sensor DTCs are set. Key is in RUN position. Engine is not running.
2. Run Test No generator, CKP sensors, or CMP sensor DTCs are set. Engine speed is less than 3000 RPM.

DTC sets when

1. Key On Test PCM detects a PWM signal more than 65 percent for at least 5 seconds.
2. Run Test PCM detects a PWM signal less than 5 percent for at least 15 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Start engine. Using scan tool, observe GEN - F TERMINAL SIGNAL parameter in PCM data list. If scan tool indicates GEN - F TERMINAL SIGNAL parameter is 5-95 percent, go to next step. If scan tool does not indicate GEN - F TERMINAL SIGNAL parameter is 5-95 percent, go to step 4 .
3. Using scan tool, command generator off. If GEN - F TERMINAL SIGNAL equals zero percent, problem is intermittent. If GEN - F TERMINAL SIGNAL does not equal zero percent, go to next step.
4. Turn ignition off. Disconnect generator connector. Connect test light to battery voltage. Turn ignition on, engine off. Probe generator connector terminal "C" (Gray wire). Observe GEN - F TERMINAL SIGNAL parameter in PCM data list. If GEN - F TERMINAL SIGNAL parameter near specified 100 percent, see CHARGING SYSTEM TEST in appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If GEN - F TERMINAL SIGNAL parameter is not near 100 percent, go to next step.
5. Check Gray wire between generator and PCM for short or open. If problem was found, repair as necessary. After repairs, go to step 8 . If problem was not found, go to next step.
6. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 8 . If problem was not found, go to next step.
7. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
8. Record scan tool FAIL RECORDS data. Clear any DTCs. Operate vehicle within FAIL RECORDS conditions as noted. Using scan tool, monitor SPECIFIC DTC info for this DTC. If scan tool indicates DTC did not fail this ignition cycle, system is okay.

DTC P0705: TRANSMISSION RANGE SWITCH CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

Transmission Range (TR) switch is part of park/neutral position and back-up light switch assembly and is mounted on transmission manual shaft. TR switch is a multi-signal switch. PCM supplies ignition voltage to TR switch on 4 signal circuits (A, B, C, and P). Each gear selector lever position grounds one or more of the signal circuits in a unique pattern. In order to determine gear range selected by driver, PCM compares voltage combination on signal circuits to a TR switch combination table stored in memory. (Scheme 15)

When PCM detects an invalid combination of TR switch signals, then DTC P0705 sets.

1. System voltage is 8-18 volts.
2. Engine run time is more than 5 seconds.
3. Vehicle speed is more than 5 MPH.

DTC sets when combination of TR switch signals is invalid for 5 seconds. (Scheme 15)

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Select TR SW. on scan tool. Using scan tool, observe TR SW. display while selecting each transmission range: P, R, N, D4, D3, D2 and D1. If each selected transmission range matches scan tool TR SW. display, problem is intermittent. If each selected transmission range does not match scan tool TR SW. display, go to next step.
3. Inspect PNP switch assembly for damage, loose or missing mounting hardware and proper adjustment. Inspect shift cable for damaged or stretched cable and proper adjustment. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to next step.
4. Using scan tool, observe TR SW. A/B/C/P display. If scan tool TR SW. A/B/C/P parameter indicates HI for all range signal states, go to step 13. If scan tool TR SW. A/B/C/P parameter does not indicate HI for all range signal states, go to next step.
5. Turn ignition off. Disconnect TR switch 4-way connector. TR switch is located on transaxle at shift lever. Turn ignition on, engine off. If scan tool TR SW. A/B/C/P parameter indicates HI for all range signal states, go to next step. If scan tool TR SW. A/B/C/P parameter does not indicate HI for all range signal states, go to step 10.
6. Using DVOM and Connector Test Adapter Kit (J 35616-A), measure voltage between TR switch 4-way connector terminal "A" (White wire) and ground. (Scheme 16) Measure voltage between TR switch 4-way connector terminal "B" (Yellow wire) and ground. Measure voltage between TR switch 4-way connector terminal "C" (Gray wire) and ground. Measure voltage between TR switch 4-way connector terminal "D" (Black/White wire) and ground. If voltage measure is 10-12 volts at all 4 terminals, go to next step. If voltage is not 10-12 volts at all 4 terminals, go to step 11.
7. Connect fused jumper wire between TR switch 4-way connector terminal "D" (Black/White wire) and ground while monitoring scan tool TR SW. A/B/C/P parameter. When signal "A" circuit (Black/White wire) is grounded, if any other signal circuits indicate LOW, go to step 12. When signal "A" circuit (Black/White wire) is grounded and no other signal circuits indicate LOW, go to next step.
8. Connect fused jumper wire between TR switch 4-way connector terminal "B" (Yellow wire) and ground while monitoring scan tool TR SW. A/B/C/P parameter. When signal "B" circuit (Yellow wire) is grounded, if any other signal circuits indicate LOW, go to step 12. When signal "B" circuit (Yellow wire) is grounded and no other signal circuits indicate LOW, go to next step.
9. Connect fused jumper wire between TR switch 4-way connector terminal "C" (Gray wire) and ground while monitoring scan tool TR SW. A/B/C/P parameter. When signal "C" circuit (Gray wire) is grounded, if any other signal circuits indicate LOW, go to step 12. When signal "C" circuit (Gray wire) is grounded and no other signal circuits indicate LOW, go to step 14.
10. Check signal circuit(s) (Black/White wire, Yellow wire, Gray wire and White wire) of TR switch that did not indicate HI for short to ground. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 15.
11. Check signal circuit(s) (Black/White wire, Yellow wire, Gray wire and White wire) of TR switch that did not indicate proper voltage for open. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 15.
12. Check affected signal circuits of TR switch for shorted together condition. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 15.
13. Check Black/White wire between TR switch 7-pin connector and ground for open. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to next step.
14. Replace TR switch. TR switch is part of park/neutral position switch. After repairs, go to step 16.
15. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
16. Perform the following procedure in order to verify repair: Select DTC. Select CLEAR INFO. Road test vehicle. Select SPECIFIC DTC. Enter DTC P0705. If DTC does not reset, system is okay.

Scheme 15

Scheme 16

Monitor scan tool while moving related connectors and wiring harness. Whenever a fault is detected, scan data will change from HI to LOW or from LOW to HI. Moving gear selector slowly through each gear while monitoring scan tool may also isolate problem.

Brake switch indicates brake pedal status to PCM. Normally-closed brake switch supplies ignition voltage to PCM. Applying brake pedal opens switch, interrupting voltage to PCM. Releasing brake pedal resumes voltage to PCM. When PCM senses zero volts at brake switch input, PCM de-energizes Torque Converter Clutch (TCC) solenoid valve.

When PCM detects an open brake switch (stuck ON) during accelerations, then DTC P0719 sets.

1. Ignition switch is on and system voltage is 8-18 volts.

DTC sets if PCM detects an open brake switch or circuit (zero volts) for 15 minutes and the following conditions occur 8 times

1. Vehicle speed is less than 5 MPH
2. Then, vehicle speed is 5-20 MPH for 3 seconds
3. Then, vehicle speed is more than 20 MPH for 6 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Record DTC FAILURE RECORDS. Clear DTC. Select BRAKE SWITCH on scan tool. Disconnect brake switch connector. Using Connector Test Adapter Kit (J 35616-A), install fused jumper wire between brake switch connector terminals "A" and "B". If brake switch status changes from open to closed, go to step 5 . If brake switch status does not change from open to closed, go to next step.
3. Remove ERLS fuse (10-amp) on "J" body or CRUISE fuse (10-amp) on "N" body. Inspect fuse for open. If fuse is open, go to next step. If fuse is not open, go to step 6 .
4. Repair short to ground in Pink wire on "J" body or Brown wire on "N" body between brake switch and fuse block. After repairs, go to step 9 .
5. Inspect brake switch for proper adjustment. Adjust brake switch as necessary. If brake switch required adjustment, go to step 9 . If brake switch did not require adjustment, go to step 7 .
6. Check Pink wire on "J" body or Brown wire on "N" body between brake switch and fuse block for open. Check Purple wire between brake switch and PCM for open. If problem was found, repair as necessary. After repairs, go to step 9 . If problem was not found, go to step 8 .
7. Replace brake switch. After repairs, go to step 9 .
8. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
9. Perform the following procedure in order to verify repair: Select DTC. Select CLEAR INFO. Turn ignition on, engine off. Apply and release brake pedal. PCM must receive 12 volts (brake switch closed) on circuit. Select SPECIFIC DTC. Enter DTC P0719. If DTC does not reset, system is okay.

Brake switch indicates brake pedal status to PCM. Normally-closed brake switch supplies ignition voltage to PCM. Applying brake pedal opens switch, interrupting voltage to PCM. Releasing brake pedal resumes voltage to PCM. When PCM senses zero volts at brake switch input, PCM de-energizes Torque Converter Clutch (TCC) solenoid valve.

When PCM detects a closed brake switch (stuck OFF) during decelerations, then DTC P0724 sets.

1. Ignition is on.
2. System voltage is 8-18 volts.

DTC sets if PCM detects a closed brake switch or circuit (12 volts) during vehicle deceleration and the following conditions occur 8 times

1. Vehicle speed is more than 20 MPH for 6 seconds
2. Then, vehicle speed is 5-20 MPH for 3 seconds
3. Then, vehicle speed is less than 5 MPH.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Record DTC FAILURE RECORDS. Clear DTC. Select BRAKE SWITCH on scan tool. Disconnect brake switch connector. If brake switch status changes from closed to open, go to step 4 . If brake switch status does not change from closed to open, go to next step.
3. Check Purple wire between brake switch, brakelights and PCM for short to voltage. If problem was found, repair as necessary. After repairs, go to step 6 . If problem was not found, go to step 5 .
4. Replace brake switch. After repairs, go to step 6 .
5. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
6. Perform the following procedure in order to verify repair: Select DTC. Select CLEAR INFO. Turn ignition on, engine off. Apply brake pedal for at least 3 seconds. Select SPECIFIC DTC. Enter DTC P0724. If DTC does not reset, system is okay.

DTC P1133: O2S1 INSUFFICIENT SWITCHING

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM continuously monitors Oxygen Sensor (O2S1) activity for 100 seconds. During monitor period, PCM counts number of times O2S1 switches from rich to lean and from lean to rich. You can determine a total for all switches with this information. If number of switches is too low, DTC P1133 will set.

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201-P0204, P0300, P0301-P0304, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set.
2. Engine Coolant Temperature (ECT) is more than 158°F (70°C).
3. Engine speed is 1600-2450 RPM.
4. Engine is operating in closed loop.
5. Throttle Position (TP) angle is between 9-18 percent.
6. Evaporative emissions control system is commanded open for more than 36 percent.
7. Purge learned memory is more than approximately 0.78.
8. Fuel level is more than 10 percent.
9. Diagnostic test completes when 30 seconds of accumulated time has been spent in specified conditions.

DTC sets when number of rich to lean counts is less than 2, or lean to rich counts is less than 2.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on, engine off. Install scan tool. If any component DTCs are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If no component DTCs are set, go to next step.
3. Start engine. Idle engine at normal operating temperature. Operate vehicle within code enable criteria. If scan tool indicates DTC failed this ignition cycle, go to next step. If scan tool does not indicate DTC failed this ignition cycle, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
4. Turn ignition off. Inspect the following conditions: Check O2S1 is securely installed. Inspect for corrosion on terminals. Inspect for terminal tension at O2S1 electrical connector and PCM electrical connector. Inspect O2S1 ground circuit for a good connection. Inspect for any damaged wiring. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to next step.
5. Start engine. Inspect exhaust manifold for an exhaust leak near engine. If a problem is found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to next step.
6. Turn ignition off. Disconnect O2S1 electrical connector at sensor. Turn ignition on, engine off. If scan tool indicates O2S1 voltage is 351-551 millivolts, go to next step. If scan tool does not indicate O2S1 voltage is 351-551 millivolts, go to step 10 .
7. Connect jumper wire between O2S1 connector (Purple wire), on PCM side and ground. If scan tool indicates O2S1 voltage is less than 20 millivolts, go to next step. If scan tool does not indicate O2S1 voltage is less than 20 millivolts, go to step 11 .
8. Check O2S1 sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to next step.
9. Turn ignition off. Replace O2S1. See OXYGEN SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repair, go to step 17 .
10. Turn ignition off. Repair short to ground in Purple wire between O2S1 and PCM. After repair, go to step 17 .
11. Remove jumper wire. Using DVOM, measure voltage between O2S1 connector (Purple wire) and ground. If O2S1 voltage is more than 407 millivolts, go to next step. If O2S1 voltage is not more than 407 millivolts, go to step 13 .
12. Turn ignition off. Disconnect PCM electrical connectors. Measure resistance in Tan wire between O2S1 and PCM. If resistance is more than 5 ohms, repair as necessary. After repairs, go to step 17 . If resistance does not measure more than 5 ohms, go to step 14 .
13. Turn ignition off. Disconnect PCM electrical connectors. Measure resistance of Purple wire between O2S1 and PCM. If resistance is more than 5 ohms, repair as necessary. After repairs, go to step 17 . If resistance does not measure more than 5 ohms, go to step 15 .
14. Check Tan wire for poor connection at PCM. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 16 .
15. Check Purple wire for poor connection at PCM. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 16 .
16. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
17. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If DTC does not reset, go to next step.
18. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

DTC P1133 is most likely caused by one of the following conditions

1. High Fuel Pressure System will go rich if fuel pressure is to high. PCM can compensate for some increase, however, if fuel pressure becomes too high, DTC P0172 will be set.
2. Leaking Injector Leaking or malfunctioning injector can cause system to go rich.
3. Manifold Absolute Pressure (MAP) Sensor Output that causes PCM to sense a higher than normal manifold pressure, indicative of a low vacuum, can cause system to go rich. Disconnecting MAP sensor will allow PCM to set a fixed value for MAP sensor. Substitute a different MAP sensor if rich condition is gone while sensor is disconnected.
4. Pressure Regulator Check for a leaking fuel pressure regulator diaphragm by checking for presence of liquid fuel in vacuum line to regulator.
5. Throttle Position (TP) Sensor Intermittent TP sensor output will cause system to go rich due to a false indication of engine accelerating.
6. O2S1 Contamination Inspect O2S1 for silicone contamination from fuel or use of improper RTV sealant. Sensor may have a White powdery coating, which may result in a high but false voltage signal, indicating a rich exhaust condition. PCM will then reduce amount of fuel that is delivered to engine, causing a severe surge or driveability problem.

DTC P1137: REAR HO2S CIRCUIT LOW VOLTAGE DURING POWER ENRICHMENT

Note. For circuit reference, see WIRING DIAGRAMS article.

In order to control emissions, a catalytic converter converts any harmful exhaust emissions into harmless water vapor and carbon dioxide.

PCM has capability to monitor this process by using a rear-heated oxygen sensor (HO2S2). HO2S2, located in exhaust stream past catalytic converter, produces an output signal which indicates storage capacity of catalyst. This in turn indicates catalysts ability to convert exhaust emissions effectively. If catalyst is functioning properly, HO2S2 signal will be far less active than signal produced by front Oxygen Sensor (O2S1).

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0172, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0336, P0440, P0446, P0452, P0453, P0506, P0507, P0601, P0602, or P1441 are not set.
2. Engine is in power enrichment mode.
3. Battery voltage is more than 10.0 volts.
4. Engine Coolant Temperature (ECT) is more than 158°F (70°C).
5. Fuel level is more than 10 percent.
6. Engine has been running more than 10 seconds.

DTC sets when HO2S2 remains less than 400 millivolts for more than 5 seconds. Diagnostic then will run for 11 seconds after a 5-second delay.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. If any other DTCs are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions). If no other DTCs are set, go to next step.
3. Turn ignition on, engine off. Using scan tool, observe HO2S2 voltage. If HO2S2 voltage is less than 22 millivolts, go to step 5. If HO2S2 voltage is not less than 22 millivolts, go to next step.
4. Review FREEZE FRAME data, and record parameters. Start engine. Operate vehicle within FREEZE FRAME conditions and code enable criteria. If HO2S2 voltage is less than 40 millivolts, go to next step. If HO2S2 voltage is not less than 40 millivolts, go to step 10.
5. Turn ignition off. Disconnect HO2S2 sensor. HO2S2 is located in exhaust stream past catalytic converter. Connect jumper wire between HO2S2 connector terminal "A" (Tan/White wire) and ground. (Scheme 10) Turn ignition on, engine off. Using DVOM, measure voltage on HO2S2 connector terminal "B" (Purple/White wire) on PCM side. If voltage is 351-551 millivolts, go to step 8. If voltage is not 351-551 millivolts, go to next step.
6. Turn ignition off. Disconnect PCM electrical connectors. Check Purple/White wire between HO2S2 and PCM for short to ground or short to Tan/White wire. If problem was found, repair as necessary. After repairs, go to step 10. If problem was not found, go to next step.
7. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 10.
8. Check HO2S2 sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 10. If problem was not found, go to next step.
9. Turn ignition off. Replace HO2S2 sensor. See OXYGEN SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
10. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If DTC does not reset, go to next step.
11. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

1. Exhaust System Inspect exhaust system for leaks, corrosion between 3-way catalytic converter and flange, loose or missing hardware.
2. Poor Electrical Connection Or A Damaged Harness Inspect harness for short to ground in HO2S2 high signal circuit. Ensure that HO2S2 pigtail is not contacting exhaust. Check for wiring contacting exhaust system, improper mating, broken locks, improperly formed harness connectors, damaged terminals, poor terminal-to-wire connection and damaged harness.
3. Intermittent Test Observe HO2S2 on scan tool while moving any related electrical connectors and wiring harness with ignition on. If malfunction is induced, HO2S2 display will change. This should help isolate location of malfunction.

An intermittent could be result of a poor electrical connection, rubbed through wire insulation or broken wire inside insulation.

Obstruction of air reference and degraded HO2S2 performance could result in any attempt to repair HO2S2 harness or connector.

HO2S2 must have a clean air reference in order for HO2S2 to function properly. This clean air reference is obtained by way of HO2S2 wires.

DTC P1138: REAR HO2S CIRCUIT HIGH VOLTAGE DURING DECEL FUEL CUTOFF

Note. For circuit reference, see WIRING DIAGRAMS article.

In order to control emissions, a 3-way catalytic (TWC) converter converts any harmful exhaust emissions into harmless water vapor and carbon dioxide.

The powertrain control module (PCM) has the capability to monitor this process by using a rear Heated Oxygen Sensor (HO2S2). The HO2S2, located in the exhaust stream past the TWC converter, produces an output signal which indicates the storage capacity of the catalyst. This in turn indicates the catalysts ability to convert the exhaust emissions effectively. If the catalyst is functioning properly, the HO2S2 signal will be far less active than the signal produced by the front Oxygen Sensor (O2S1).

1. DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0172, P0201-P0204, P0300, P0301-P0304, P0336, P0440, P0446, P0452, P0453, P0506, P0507, P0601, P0602, or P1441 are not set.
2. Engine is in Decel Fuel Cut-Off (DFCO) mode.
3. Battery voltage is more than 10 volts.
4. Engine Coolant Temperature (ECT) is more than 158°F (70°C).
5. Fuel level is more than 10 percent.
6. Engine has been running for more than 10 seconds.

DTC sets when HO2S2 remains at more than 648 millivolts for more than 10 seconds. Diagnostic then will run for 11 seconds after a 10-second delay in order to complete one test.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. If any other DTCs are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions). If no other DTCs are set, go to next step.
3. Using scan tool, observe HO2S2 voltage. If HO2S2 sensor voltage is more than 1042 millivolts, go to step 5. If HO2S2 sensor voltage is not more than 1042 millivolts, go to next step.
4. Review FREEZE FRAME data, and record parameters. Start engine. Operate vehicle within FREEZE FRAME conditions and code enable criteria. If HO2S2 sensor voltage is more than 1042 millivolts, go to next step. If HO2S2 sensor voltage is not more than 1042 millivolts, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
5. Turn ignition off. Disconnect HO2S2 electrical connector. HO2S2 is located in exhaust stream past catalytic converter. Disconnect PCM connectors. Connect DVOM to ground. Turn ignition on, engine off. probe HO2S2 connector terminal "B" (Purple/White wire). (Scheme 10) If voltage is near zero volts, go to next step. If voltage is not near zero volts, go to step 7.
6. Turn ignition off. Reconnect PCM electrical connectors. Turn ignition on, engine off. Connect jumper wire between HO2S2 connector terminals "A" (Tan/White wire), "B" (Purple/White wire) and ground. If scan tool indicates HO2S2 sensor voltage is less than 100 millivolts, go to step 8. If scan tool does not indicate HO2S2 sensor voltage is less than 100 millivolts, go to step 10.
7. Repair short to voltage in Purple/White wire between HO2S2 and PCM. After repairs, go to step 11.
8. Check HO2S2 sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 11. If problem was not found, go to next step.
9. Replace HO2S2 sensor. See OXYGEN SENSOR in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 11.
10. Turn ignition off. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
11. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If DTC does not reset, go to next step.
12. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions).

1. Rich Exhaust An overly rich exhaust may load catalyst and cause high HO2S2 signal voltages.
2. Silicone Contamination Silicone contamination of HO2S2 could cause a false rich condition. A powdery White deposit on sensor will indicate this condition.
3. Malfunctioning HO2S If there is an internal short in HO2S2, HO2S2 voltage that is displayed on a scan tool will be more than one volt. Disconnect HO2S2 and connect jumper wire between HO2S2 low signal circuit to engine ground. Replace HO2S2 if displayed voltage goes from more than 1000 millivolts to approximately 450 millivolts.
4. Intermittent Test Observe HO2S2 on scan tool while moving related electrical connectors and wiring harness with ignition turned on. If malfunction is induced, HO2S2 display will change. This should help to isolate location of malfunction.
5. Damaged Harness Inspect PCM harness for short to voltage in HO2S2 high signal circuit.

An intermittent could be result of a poor electrical connection, rubbed through wire insulation or broken wire inside insulation.

Obstruction of air reference and degraded HO2S2 performance could result in any attempt to repair HO2S2 harness or connector.

HO2S2 must have a clean air reference in order for HO2S2 to function properly. This clean air reference is obtained by way of HO2S2 wires.

DTC P1171: FUEL SYSTEM LEAN DURING ACCELERATION

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM can identify if vehicle fuel system is capable of supplying adequate amounts of fuel during heavy acceleration. This condition is called a power enrichment mode of operation. If power enrichment is requested during a closed loop operation, PCM will provide more fuel to engine. Under these conditions, PCM should detect a rich condition. If PCM does not detect a rich exhaust at this time, DTC will set. A plugged fuel filter, or a restricted fuel line can prevent adequate amounts of fuel from being supplied during power enrichment mode.

1. DTCs P0131, P0132, P0133, P0134, or P1133 are not set.
2. Engine Coolant Temperature (ECT) is more than 70°F (20°C).
3. Engine has been running for more than 20 seconds.
4. Engine is operating in a closed loop operation.

DTC sets when O2S1 voltage is less than 300 millivolts for 5 seconds and engine is in power enrichment mode.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on, engine off. Install scan tool. If any component DTCs are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If no component DTCs are set, go to next step.
3. Inspect vehicle for an adequate amount of fuel. Add fuel to vehicle fuel tank if tank is almost empty. If fuel was added, go to step 5 . If fuel was not added, go to next step.
4. Start engine. Run engine at 167-203°F (75-95°C) and 1200 RPM. Observe O2S1 voltage using scan tool. O2S1 voltage should vary from 100-900 millivolts and occasionally toggle to more than 447 millivolts. If O2S1 toggles, see FUEL SYSTEM under appropriate SYSTEM & COMPONENT TESTING article. If O2S1 does not toggle, see «DTC P0134: O2S1 CIRCUIT - INSUFFICIENT ACTIVITY»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__dtc-p0134-o2s1-circuit-insufficient) .
5. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If DTC does not reset, go to next step.
6. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

1. A restricted fuel filter can supply adequate amounts of fuel at idle, but may not be able to supply enough fuel during a heavy acceleration.
2. Water or alcohol in fuel may cause a low O2S1 voltage during acceleration.
3. Check for an adequate amount of fuel in fuel tank.
4. When engine is idling or at steady cruise, O2S1 voltage should vary from approximately 100 millivolts to 900 millivolts. During power enrichment mode, more fuel is needed and O2S1 voltage should rise to more than 447 millivolts.
5. Check for malfunctioning or plugged injectors.

Gas Mass Sensor (GMS) and Mixture Control Valve (MCV) are contained in one non-serviceable assembly. GMS monitors mass and flow of gaseous fuel entering engine and converts this information into a GMS ACTUAL GAS FLOW signal circuit frequency. Alternate Fuel Engine Control Module (AF ECU) commands fuel flow by supplying MCV with a frequency signal. DESIRED GAS FLOW signal circuit frequency varies from 1050 Hz (0.40 gm/s) at idle, to 5000 Hz (18 gm/s) at wide open throttle.

AF ECU converts ACTUAL GAS FLOW signal circuit frequency into a grams per second value. During low fuel flow rates (such as at engine idle) GMS sensor actual gas circuit will produce a low frequency signal of approximately 700 Hz (0.21 gm/s). During high fuel flow rates (such as at wide open throttle-road load) GMS sensor will produce a high frequency signal of approximately 2700 Hz (16.65 gm/s). AF ECU monitors and compares actual gas flow rate to a calculated gas flow rate. Calculated gas flow rate is based upon a calculated Mass Air Flow (MAF) rate.

For DTC to run, the following conditions must be met

1. Engine is operating on alternative fuel.
2. No AF ECU ECT, O2S or GMS DTCs are set.
3. Engine speed is more than 500 RPM.
4. Battery voltage is more than 10 volts.
5. Fuel Pressure Sensor (FPS) indicates CNG fuel level is more than one-quarter full.
6. Engine coolant temperature is 176-221°F (80-105°C).
7. AF ECU is not operating in fuel cut-off mode (DFCO, speed limiting, etc.).

DTC will set when difference between Desired Gas Flow and Actual Gas Flow is more than 45 percent for 5 seconds. When DTC is set, AF ECU will switch-over to gasoline fuel operation. AF ECU will not attempt alternative fuel operation until next ignition key cycle.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Using scan tool, capture AF ECU DTC information. Check PCM and AF ECU for additional DTCs. If additional DTCs are set, go to next step. If additional DTCs are not set, go to step 4.
3. Diagnose these DTCs first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions). After repairs, go to step 12.
4. Check vehicle for the following malfunction conditions: An open or shorted O2S signal wire. O2S connector water intrusion. Leaking exhaust system. Poor GMS/MCV connector terminal contact. Inadequate ignition voltage or ground circuits to GMS/MCV. Misrouted engine harness causing EMI interference on actual gas circuit. Rich or lean engine condition such as EVAP canister purge system malfunction, gasoline contaminated engine oil, incorrect CNG fuel pressure, leaking gasoline fuel pressure regulator, restricted air filter or intake air duct, engine vacuum leak, or an improperly operating PCV system. Repair as necessary. After repairs, go to step 12. If no conditions are found, go to next step.
5. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, go to next step. If DTC resets, go to step 7.
6. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
7. Perform fuel system diagnosis. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS (2.2L - CAVALIER CNG) in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article. Repair as necessary. After repairs, go to step 12. If fuel system diagnosis passes, go to next step.
8. Disconnect Oxygen Sensor (O2S), PCM and AF ECU connectors. PCM is located inside right front fender. AF ECU is located behind left front fascia, below headlight. Ensure continuity exists in Purple wire between AF ECU White/Clear connector C002 terminal No. 4 and splice S015 located approximately 12" (29.5 cm) from IAT sensor breakout, towards oxygen sensor breakout. (Scheme 3) Ensure continuity exists in Tan wire between AF ECU White/Clear connector C002 terminal No. 5 and splice S014 located approximately 9" (23 cm) from IAT sensor breakout, towards oxygen sensor breakout. Check for short to ground, short to signal circuit or short to other circuits in Purple and Tan wires. Repair as necessary. After repairs, go to step 12. If circuits are okay, go to next step.
9. Reconnect all disconnected components and connectors. Ensure ignition is off. Using scan tool, clear DTCs for PCM and AF ECU and reset Fuel Trim values to zero. Remove CNG fuse (20-amp) from underhood fuse block. This will cause a forced switch to gasoline operation. Start engine and view captured data freeze frame records for this DTC. Observe data parameters that indicate how vehicle was being operated when DTC set. Operate vehicle within conditions for running this DTC. See «CODE ENABLE CRITERIA»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l). Observe short term fuel trim value. If fuel trim value indicates a large amount of fuel trim adjustment is required or if fuel trim DTCs set, go to next step. If fuel trim value does not indicate a large amount of fuel trim adjustment is required or if no fuel trim DTCs set, go to step 11.
10. Repair possible causes of excessive rich or lean engine operation. Refer to items in step 4. After repairs, go to step 12.
11. Replace Gas Mass Sensor and Mixture Control Valve (GMS/MCV). (Scheme 12) After repairs, go to next step.
12. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Connect scan tool and perform a snapshot of AF ECU data parameters when this DTC sets. Compare actual gas circuit gas flow to mass air flow to determine if a rich or lean condition is occurring. (Scheme 17) If actual gas circuit flow is more than high limit, then GMS/MCV is adding fuel to compensate for a lean engine condition.

Problem may also be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Scheme 17

Gas Mass Sensor (GMS) and Mixture Control Valve (MCV) are contained in one non-serviceable assembly. GMS monitors mass and flow of gaseous fuel entering engine and converts this information into a GMS ACTUAL GAS FLOW signal circuit frequency. Alternate Fuel Engine Control Module (AF ECU) commands fuel flow by supplying MCV with a frequency signal. DESIRED GAS FLOW signal circuit frequency varies from 1050 Hz (0.40 gm/s) at idle, to 5000 Hz (18 gm/s) at wide open throttle.

AF ECU converts ACTUAL GAS FLOW signal circuit frequency into a grams per second value. During low fuel flow rates (such as at engine idle) GMS sensor actual gas circuit will produce a low frequency signal of approximately 700 Hz (0.21 gm/s). During high fuel flow rates (such as at wide open throttle-road load) GMS sensor will produce a high frequency signal of approximately 2700 Hz (16.65 gm/s). AF ECU monitors and compares actual gas flow rate to a calculated gas flow rate. Calculated gas flow rate is based upon a calculated Mass Air Flow (MAF) rate.

DTC will run under 2 conditions, engine cranking and engine running. For DTC to run while engine is cranking, engine must be cranking on alternative fuel with engine speed 25-500 RPM and battery voltage more than 8 volts. For DTC to run while engine is running, the following conditions must be met

1. Engine is operating on alternative fuel.
2. Engine has been operating for more than 10 seconds.
3. Engine speed is more than 500 RPM.
4. Battery voltage is more than 10 volts.

While engine is cranking, DTC will set when AF ECU detects GMS actual gas flow signal circuit frequency of less than 250 Hz for at least 0.5 continuous second. While engine is running, DTC will set when AF ECU detect GMS actual gas flow signal circuit frequency of less than 500 Hz for at least 0.5 continuous second. When DTC is set, AF ECU will switch-over to gasoline fuel operation. AF ECU will not attempt alternative fuel operation until next ignition key cycle.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Using scan tool, capture AF ECU DTC information. Check PCM and AF ECU for additional DTCs. If additional DTCs are set, go to next step. If additional DTCs are not set, go to step 4.
3. Diagnose these DTCs first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions). After repairs, go to step 25.
4. Using scan tool, communicate with AF ECU and monitor ENGINE SPEED. Attempt to start engine. If engine speed is indicated while engine is cranking, go to next step. If engine speed is not indicated while engine is cranking, go to step 23.
5. Using scan tool, clear AF ECU DTCs. Turn ignition off and wait 30 seconds. Start engine and view captured data freeze frame records on scan tool for this DTC. Operate vehicle within conditions to set DTC. See «CODE ENABLE CRITERIA»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l). If DTC runs and passes, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l). If DTC resets, go to next step.
6. Turn ignition off. Check for poor connections at Gas Mass Sensor and Mixture Control Valve (GMS/MCV) connector. (Scheme 12) Check for continuity of Gray wire between GMS connector terminal No. 24 and MCV connector terminal "A". (Scheme 18) Check for continuity of Pink wire between GMS connector terminal No. 23 and MCV connector terminal "B". Repair as necessary. After repairs, go to step 25. If connections and circuits are okay, go to next step.
7. Disconnect GMS/MCV connector. Turn ignition on. Using DVOM, measure voltage between ground and GMS connector terminal No. 9 (Red wire). If voltage is 11-13 volts, go to next step. If voltage is not 11-13 volts, go to step 15.
8. Connect test light between GMS connector terminals No. 9 (Red wire) and No. 21 (Black wire). Move test light from terminal No. 21 to terminal No. 22 (Black wire). If test light illuminates brightly at both terminals, go to next step. If test light does not illuminate brightly at both terminals, go to step 16.
9. Using DVOM, measure voltage between GMS connector terminal No. 6 (Pink wire) and ground. If voltage is approximately 5 volts, go to next step. If voltage is not approximately 5 volts, go to step 17.
10. Ensure ignition is on. Connect a test light between GMS connector terminals No. 7 (Dark Blue wire) and No. 9 (Red wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 18.
11. Turn ignition off. If test light turns off, go to next step. If test light does not turn off, go to step 19.
12. Reconnect all disconnected components and connectors. Using scan tool, clear AF ECU DTCs. Turn ignition off. Connect Fuel Test Port Adapter (J 39970-100) to CNG fuel pressure test port. (Scheme 12) Connect Electronic Pressure Gauge (J 39200) to adapter. Monitor fuel pressure while cranking and starting engine. If fuel pressure is ever more than 115 psi, go to next step. If fuel pressure is never more than 115 psi, diagnose fuel pressure. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS (2.2L - CAVALIER CNG) in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article.
13. Turn ignition off. Remove fuel test port adapter. Remove fuel pump relay from underhood fuse block. (Scheme 11) Turn ignition on. Using scan tool, clear AF ECU DTCs. Using scan tool, observe NGO ENABLE INPUT parameter and ensure alternative fuel is enabled. An ignition cycle with a 30 second OFF time may be required to enable alternative fuel after clearing DTCs. Using DVOM connected to ground, backprobe GMS connector terminal No. 7 (Dark Blue wire). Set DVOM to AC volts to observe frequency. Crank engine while observing frequency for approximately 5 seconds or until a switch-over to gasoline is observed. Engine will not start with fuel pump relay removed. If frequency is more than 750 Hz, go to next step. If frequency is less than 750 Hz, go to step 20.
14. Using DVOM connected to ground, backprobe GMS connector terminal No. 6 (Pink wire). Ensure DVOM is set the AC volts to measure frequency. Crank engine while observing frequency for approximately 5 seconds or until a switch-over to gasoline is observed. Engine will not start with fuel pump relay removed. If frequency is more than 250 Hz, go to step 24. If frequency is less than 250 Hz, go to step 22.
15. Turn ignition off and wait 30 seconds. Observe Fuel Indicator Light (FIL) located on left side of steering column. Turn ignition on. If FIL illuminates for 2 seconds during bulb check or FIL stays on, go to step 21. If FIL does not illuminate for 2 seconds during bulb check or stay on, diagnose ignition relay. See IGNITION RELAY DIAGNOSIS (2.2L - CAVALIER - CNG) under IGNITION SYSTEM in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article.
16. Repair open or high resistance in suspect Black wire between GMS and splice S006 located approximately 18 " from ground connection located on left side of engine/transmission. After repairs, go to step 25.
17. Check for short to ground, short to voltage or open in Pink wire between GMS connector terminal No. 6 and AF ECU Blue connector C001 terminal No. 19. (Scheme 3) Check for poor connections at GMS and AF ECU. Repair as necessary. After repairs, go to step 25. If circuit and connections are okay, go to step 24.
18. Check for short to voltage or open in Dark Blue wire between GMS connector terminal No. 7 and AF ECU Blue connector C001 terminal No. 9. (Scheme 3) Check for poor connections at GMS and AF ECU. Repair as necessary. After repairs, go to step 25. If circuit and connections are okay, go to step 24.
19. Check for short to ground in Dark Blue wire between GMS connector terminal No. 7 and AF ECU Blue connector C001 terminal No. 9. (Scheme 3) Repair as necessary. After repairs, go to step 25. If circuit is okay, go to step 24.
20. Turn ignition off. Disconnect AF ECU connectors. AF ECU is located behind left front fascia, below headlight. Turn ignition on. Connect DVOM between ground and AF ECU Blue connector C001 terminal No. 9 (Dark Blue wire). (Scheme 3) If voltage is 4-6 volts, go to step 24. If voltage is not 4-6 volts, go to step 22.
21. Repair open in Red wire between GMS and splice S003 located approximately 18" from connector P001 located under steering column. (Scheme 2) After repairs, go to step 25.
22. Replace GMS/MCV. (Scheme 12) After repairs, go to step 25.
23. Check for open or high resistance in Purple/White wire between AF ECU Blue connector C001 terminal No. 18 and splice S011. (Scheme 3) S011 is located approximately 6.5" (16.5 cm) from IAT sensor harness breakout, towards oxygen sensor harness breakout. Repair as necessary. After repairs, go to step 25. If circuit is okay, go to next step.
24. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to next step.
25. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Note. Desired gas and actual gas circuits only output a frequency signal when engine is cranking or running on CNG. Frequency signal is NOT present with ignition ON and engine OFF or during any time vehicle is operating in gasoline mode.

Problem may also be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Scheme 18

Gas Mass Sensor (GMS) and Mixture Control Valve (MCV) are contained in one non-serviceable assembly. GMS monitors mass and flow of gaseous fuel entering engine and converts this information into a GMS ACTUAL GAS FLOW signal circuit frequency. Alternate Fuel Engine Control Module (AF ECU) commands fuel flow by supplying MCV with a frequency signal. DESIRED GAS FLOW signal circuit frequency varies from 1050 Hz (0.40 gm/s) at idle, to 5000 Hz (18 gm/s) at wide open throttle.

AF ECU converts ACTUAL GAS FLOW signal circuit frequency into a grams per second value. During low fuel flow rates (such as at engine idle) GMS sensor actual gas circuit will produce a low frequency signal of approximately 700 Hz (0.21 gm/s). During high fuel flow rates (such as at wide open throttle-road load) GMS sensor will produce a high frequency signal of approximately 2700 Hz (16.65 gm/s). AF ECU monitors and compares actual gas flow rate to a calculated gas flow rate. Calculated gas flow rate is based upon a calculated Mass Air Flow (MAF) rate.

DTC will run under 2 conditions, engine cranking and engine running. For DTC to run while engine is cranking, engine must be cranking on alternative fuel with engine speed 25-500 RPM and battery voltage more than 8 volts. For DTC to run while engine is running, the following conditions must be met

1. Engine is operating on alternative fuel.
2. Engine has been operating for more than 10 seconds.
3. Engine speed is more than 500 RPM.
4. Battery voltage is more than 10 volts.

While engine is cranking or running, DTC will set when AF ECU detects GMS actual gas flow signal circuit frequency of more than 2900 Hz for at least 0.5 continuous second. When DTC is set, AF ECU will switch-over to gasoline fuel operation. AF ECU will not attempt alternative fuel operation until next ignition key cycle.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Using scan tool, capture AF ECU DTC information. Clear AF ECU DTCs. Start engine and view captured data freeze frame records on scan tool for this DTC. Operate vehicle within conditions to set DTC. See «CODE ENABLE CRITERIA»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l). If DTC runs and passes, go to next step. If DTC resets, go to step 4.
3. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Turn ignition off. Locate and disconnect GMS/MCV connectors. (Scheme 12) Using DVOM, measure voltage between ground and GMS connector terminal No. 9 (Red wire). (Scheme 18) Turn ignition on. If voltage is 11-13 volts, go to next step. If voltage is not 11-13 volts, go to step 9.
5. Connect test light between GMS connector terminals No. 9 (Red wire) and No. 21 (Black wire). Move test light from terminal No. 21 to terminal No. 22 (Black wire). If test light illuminates brightly at both terminals, go to next step. If test light does not illuminate brightly at both terminals, go to step 10.
6. High frequency signal may be induced on actual gas flow signal circuit by sources other than GMS/MCV sensor. Check for actual gas flow signal circuit routed near secondary ignition components or high current components (motors, relays, etc.). Also check for high power transceivers operating in or near vehicle. Route wiring harness correctly or remove source of high frequency as necessary. After repairs, go to step 12. If interference is not found, go to next step.
7. Perform fuel system diagnosis. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS (2.2L - CAVALIER CNG) in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article. If problem is found and repaired in CNG fuel system, go to step 12. If problem is not found and repaired in CNG fuel system, go to next step.
8. Replace GMS/MCV. (Scheme 12) After repairs, go to step 12.
9. Turn ignition off and wait 30 seconds. Observe Fuel Indicator Light (FIL) located to left of steering column. Turn ignition on. If FIL illuminates for 2 seconds during bulb check or stays on, go to step 11. If FIL does not illuminate for 2 seconds during bulb check or stay on, diagnose ignition relay. See IGNITION RELAY DIAGNOSIS (2.2L - CAVALIER - CNG) under IGNITION SYSTEM in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article.
10. Repair open or high resistance in suspect Black wire between GMS and splice S006 located approximately 18 " from ground connection located on left side of engine/transmission. After repairs, go to step 12.
11. Repair open in Red wire between GMS and splice S003 located approximately 18" from connector P001 located under steering column. (Scheme 2) After repairs, go to next step.
12. Using scan tool, clear DTCs from AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Note. Desired gas and actual gas circuits only output a frequency signal when engine is cranking or running on CNG. Frequency signal is NOT present with ignition ON and engine OFF or during any time vehicle is operating in gasoline mode.

Problem may also be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Alternate Fuel Engine Control Unit (AF ECU) contains electronic devices called output driver modules. Output driver modules provide switchable outputs (control circuits) for operating solenoids, relays, telltales and other devices. Each output has an internal fault line that AF ECU can monitor for faulted circuit conditions.

Two types of outputs can be used. High side drivers supply voltage on control circuit and low side drivers supply ground on control circuit. Currently all monitored outputs are low side drivers. For fault line to detect a failure, state of control circuit must be opposite of expected state. If AF ECU is commanding an output ON, then zero volts should be monitored by fault line. If AF ECU is commanding an output OFF, then voltage should be monitored by fault line.

Monitored control circuits include Malfunction Indicator Lamp (MIL) control, NGO enable output control, high pressure and low pressure lock-off solenoid control.

For DTC to run, ignition must be on. DTC will set when AF ECU detects a control circuit fault for at least one second.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Attempt to start engine. If engine starts and runs, go to next step. If engine does not start and run, diagnose fuel lock-off relay. See FUEL LOCK-OFF RELAY DIAGNOSIS (2.2L - CAVALIER - CNG) under FUEL SYSTEM in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article.
3. Observe MIL on instrument cluster. Turn ignition on. If MIL illuminates, go to next step. If MIL does not illuminate, go to «MIL INOPERATIVE (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__mil-inoperative-cng) under SYSTEM TESTS.
4. Using scan tool, select SPECIAL FUNCTION display for alternative fuel and command AF ECU to turn MIL off. If MIL remains illuminated when commanded off, go to «MIL ON STEADY (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__mil-on-steady-cng) under SYSTEM TESTS. If MIL turns off, go to next step.
5. Ensure ignition is on. Using scan tool, observe ENGINE DATA display for alternative fuel and monitor NGO SIGNAL and NGO SIGNAL COMMAND parameters. If both parameters are the same, go to next step. If both parameters are not the same, go to step 9.
6. Turn ignition on. Use scan tool to capture DTC information from AF ECU. Clear DTCs from AF ECU. Using scan tool, select SPECIAL FUNCTION display for alternative fuel and command NGO back and forth between gasoline and CNG. Monitor NGO SIGNAL and NGO SIGNAL COMMAND parameters. If both parameters are the same, go to next step. If both parameters are not the same, go to step 9.
7. Exit special function display on scan tool. Start engine and allow to idle. Monitor NGO SIGNAL and NGO SIGNAL COMMAND parameters. If engine is operating on alternate fuel, go to next step. If engine is not operating on alternate fuel, go to step 12.
8. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
9. Using scan tool, monitor NGO signal. If NGO signal indicates gasoline, go to next step. If NGO does not indicate gasoline, go to step 11.
10. Turn ignition off. Disconnect AF ECU connectors. AF ECU is located behind left front fascia, below headlight. Connect a fused jumper wire between ground and AF ECU Blue connector C001 terminal No. 3 (Pink wire). (Scheme 3) Turn ignition on. If fused jumper blows, Pink wire is shorted to ground. Select ENGINE DATA for gasoline on scan tool and monitor NGO SIGNAL parameter. If NGO parameter indicates alternate fuel is enabled, go to step 21. If NGO parameter does not indicate alternate fuel is enabled, go to step 16.
11. Turn ignition off. Disconnect AF ECU connectors. AF ECU is located behind left front fascia, below headlight. Turn ignition on. Select ENGINE DATA for gasoline on scan tool and monitor NGO SIGNAL parameter. If NGO parameter indicates gasoline is enabled, go to step 22. If NGO parameter does not indicate gasoline is enabled, go to step 17.
12. Using a test light connected to ground, backprobe LOCK-OFF RELAY connector terminal No. 87 (Purple wire). Lock-off relay is located behind left side of front bumper, attached to bumper bar. (Scheme 2) Start engine and allow to idle. If test light is illuminated while engine is running, go to next step. If test light is not illuminated while engine is running, diagnose lock-off relay. See FUEL LOCK-OFF RELAY DIAGNOSIS (2.2L - CAVALIER - CNG) under FUEL SYSTEM in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article.
13. Turn ignition off. Locate and disconnect AF ECU connectors. AF ECU is located behind left front fascia, below headlight. Disconnect lock-off relay. Connect Red lead of DVOM to lock-off relay connector terminal No. 87 (Purple wire) and Black lead to AF ECU White/Clear connector C002 terminal No. 1 (Light Blue wire). (Scheme 3) Measure resistance. If resistance is 6.2-10.0 ohms, go to next step. If resistance is not 6.2-10.0 ohms, go to step 18.
14. With Red lead of DVOM connected, move Black lead to AF ECU White/Clear connector C002 terminal No. 3 (Light Green wire). Measure resistance. If resistance is 16.3-20.6 ohms, go to next step. If resistance is not 16.3-20.6 ohms, go to step 18.
15. Using DVOM, measure resistance between ground and AF ECU White/Clear connector C002 terminal No. 1 (Light Blue wire). Also measure resistance between ground and AF ECU White/Clear connector C002 terminal No. 3 (Light Green wire). If resistance at either terminal is less than infinite (OL), go to step 20. If resistance at both terminals is infinite (OL), go to step 22.
16. Check for open or high resistance in Pink wire between AF ECU Blue connector C001 terminal No. 3 and PCM connector C1 terminal No. 71. (Scheme 3)and (Scheme 5). Check for poor connections at PCM. Repair as necessary. After repairs, go to step 24. If connections and circuit are okay, go to step 23.
17. Check for short to ground in Pink wire between AF ECU Blue connector C001 terminal No. 3 (Pink wire) and PCM connector C1 terminal No. 71. (Scheme 3)and (Scheme 5). Repair as necessary. After repairs, go to step 24. If circuit is okay, go to step 23.
18. Disconnect suspect solenoid connector. (Scheme 12) If resistance is more than specified, check for continuity in circuit between suspect solenoid and AF ECU connector. Also check for continuity in Purple wire between suspect solenoid and lock-off relay connector. See WIRING DIAGRAMS article. If resistance is less than specified, check for shorted AF diode or short between supply and control circuit for suspect solenoid. Repair as necessary. After repairs, go to step 24. If circuits and diodes are okay, go to next step.
19. Replace suspect lock-off solenoid. See LOCK-OFF SOLENOIDS under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. After repairs, go to step 24.
20. Repair short in suspect solenoid control circuit (Light Blue or Light Green wire between solenoid and AF ECU). After repairs, go to step 24.
21. Check for poor connections at AF ECU connectors. Repair as necessary. After repairs, go to step 24.
22. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to step 24.
23. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) PCM with correct vehicle software and calibration. See «POWERTRAIN CONTROL MODULE REPROGRAMMING»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-control-module-reprogramming) under PROGRAMMING. To perform CKP variation learn procedure, a switch-over to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switch-over. Perform CKP system variation learn procedure. See «CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__crankshaft-position-sensor-system-variation-learn) under PROGRAMMING. After performing repairs and procedures, go to next step.
24. Using scan tool, clear DTCs from AF ECU and PCM. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may also be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

DTC P1336: CKP SYSTEM VARIATION NOT LEARNED

Note. For circuit reference, see WIRING DIAGRAMS article.

In order to detect an engine misfire at higher engine speeds, PCM must know of any variation between crankshaft sensor pulses. Most variations are due to machining of crankshaft reluctor wheel, however, other sources of variation are also possible. A crankshaft position system variation learn procedure must be performed any time that you perform the following service procedures, regardless of whether DTC P1336 is set

1. PCM replacement.
2. Engine replacement.
3. Crankshaft replacement.
4. Crankshaft balancer replacement.
5. Crankshaft Position (CKP) sensor replacement.
6. Any engine repairs which disturbs crankshaft/harmonic balancer to crankshaft position sensor relationship.

PCM measures variations and then calculates compensation factors needed in order to enable PCM to accurately detect an engine misfire at all speeds and loads. A scan tool must be used to command PCM to learn these variations. If for any reason PCM is unable to learn these variations or if variations are out of an acceptable range, PCM will set a DTC P1336. A DTC P1336 will also set if PCM has not had crankshaft position system variation learn procedure performed due to replacement or a reprogramming.

1. DTCs P0336, P0340, or P0341 are not set.

DTC sets when PCM has not successfully learned crankshaft position system variation.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Perform crankshaft position system variation learn procedure. See «CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__crankshaft-position-sensor-system-variation-learn) under PROGRAMMING. If scan tool indicates crankshaft position system variation has been learned, go to step 4 . If scan tool does not indicate crankshaft position system variation has been learned, go to next step.
3. Turn ignition off. Inspect crank sensor to crankshaft relationship. See «EXCESSIVE CRANKSHAFT VARIATION SYMPTOM»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) table. If problem was found, repair as necessary. After repairs, go to next step. If problem was not found, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .
4. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If DTC does not reset, go to next step.
5. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

EXCESSIVE CRANKSHAFT VARIATION SYMPTOM

Note. Before performing crankshaft position system variation learn procedure always set vehicle parking brake and block drive wheels in order to prevent personal injury. Release throttle immediately when engine starts to decelerate in order to eliminate over revving-engine. Once learn procedure is completed, control module will return engine control to operator and engine will respond to throttle position.

DTC P1336 will only set if PCM has not learned crankshaft position system variation. PCM only needs to learn this variation once per life cycle of vehicle unless crank sensor to crankshaft relationship is disturbed. Removing a part for inspection and then reinstalling same part is considered a disturbance.

Crankshaft position system variation learn procedure must be performed when replacing PCM in order to clear DTC P1336. Crankshaft position system variation learn procedure is also required when the following service procedures have been performed, regardless of whether or not DTC P1336 is set

1. PCM replacement.
2. Engine replacement.
3. Crankshaft replacement.
4. Crankshaft balancer replacement.
5. Crankshaft position sensor replacement.
6. Any engine repairs which disturbs crankshaft/harmonic balancer to crankshaft position sensor relationship.

A fully warmed up engine is critical to learning variation correctly. If a valid learn occurs, no other learns can be completed on that ignition cycle.

If engine cuts out before specified learn procedure engine speed or at normal fuel cut-off RPM, PCM is not in learn procedure mode. Review crankshaft position system variation learn procedure and re-enable learn procedure. Verify scan tool displays TEST IN PROGRESS.

Fuel Pressure Sensor (FPS) is a potentiometer. Alternate Fuel Engine Control Unit (AF ECU) supplies 5-volt reference voltage and ground circuit to FPS sensor. When fuel level/tank pressure is full, FPS signal voltage increases to 4.1 volts. As fuel level/tank pressure decreases to empty, FPS signal voltage drops to approximately 0.5 volt. AF ECU monitors FPS signal circuit voltage and Fuel Temperature Sensor (FTS) to determine amount of fuel in fuel tank.

For DTC to run, engine must be operating on alternative fuel. DTC will set when AF ECU detects an FPS signal voltage of less than 0.50 volt for at least one second.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, communicate with AF ECU. Observe FUEL PRESSURE SENSOR voltage. If FPS voltage is less than 0.5 volt, go to step 4. If FPS voltage is more than 0.5 volt, go to next step.
3. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Remove fuel tank cover in trunk to access CNG fuel tank. Locate and disconnect FPS connector. (Scheme 12) Using scan tool, monitor FPS voltage. If FPS voltage is more than 4.7 volts, go to step 8. If FPS voltage is less than 4.7 volts, go to next step.
5. Using DVOM, measure voltage between FPS connector terminals "A" (Black wire) and "B" (Red wire). If voltage is less than 4.8 volts, go to step 7. If voltage is more than 4.8 volts, go to next step.
6. Check for open, short to ground or short to sensor ground in Gray wire between FPS connector terminal "C" and AF ECU Blue connector C001 terminal No. 24. (Scheme 3) Check for poor connections at AF ECU. Repair as necessary. After repairs, go to step 11. If circuit and connections are okay, go to step 10.
7. Check for open short to ground or short to sensor ground in Red wire between FPS connector terminal "B" and AF ECU White/Clear connector C002 terminal No. 18. (Scheme 3) Check for poor connections at AF ECU. Repair as necessary. After repairs, go to step 11. If circuit and connections are okay, go to step 10.
8. Check for poor connections at FPS connector. Repair as necessary. After repairs, go to step 11. If connections are okay, go to next step.
9. Replace FPS. See FUEL TANK PRESSURE SENSOR under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. After repairs, go to step 11.
10. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to next step.
11. Using scan tool, clear DTCs from AF ECU and PCM. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may also be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Fuel Pressure Sensor (FPS) is a potentiometer. Alternate Fuel Engine Control Unit (AF ECU) supplies 5-volt reference voltage and ground circuit to FPS sensor. When fuel level/tank pressure is full, FPS signal voltage increases to 4.1 volts. As fuel level/tank pressure decreases to empty, FPS signal voltage decreases to approximately 0.5 volt. AF ECU monitors FPS signal circuit voltage and Fuel Temperature Sensor (FTS) to determine amount of fuel in fuel tank.

For DTC to run, engine must be operating on alternate fuel. DTC will set when AF ECU detects an FPS signal voltage of more than 4.7 volts for at least one second.

1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-cng) under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, communicate with AF ECU. Observe FUEL PRESSURE SENSOR voltage. If FPS voltage is more than 4.7 volts, go to step 4. If FPS voltage is less than 4.7 volts, go to next step.
3. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l).
4. Using scan tool, monitor Fuel Temperature Sensor (FTS) voltage. If FTS voltage is more than 4.7 volts, go to step 8. If FTSvoltage is less than 4.7 volts, go to next step.
5. Remove fuel tank cover in trunk to access CNG fuel tank. Locate and disconnect FPS connector. (Scheme 12) Connect a fused jumper between ground and FPS connector terminal "C" (Gray wire). Using scan tool, monitor FPS voltage. If FPS voltage is less than 0.25 volt, go to step 9. If FPS voltage is more than 0.25 volt, go to next step.
6. Remove jumper wire. Using DVOM, measure voltage between FPS connector terminals "A" (Black wire) and "B" (Red wire). If voltage is more than 5.2 volts, go to step 10. If voltage is less than 5.2 volts, go to next step.
7. Connect test light between battery voltage and FPS connector terminal "A". If test light illuminates, go to step 12. If test light does not illuminate, go to step 11.
8. Check for open or high resistance in Black wire between FPS connector terminal "A" and AF ECU White/Clear connector C002 terminal No. 19. (Scheme 3) Check for poor connections at AF ECU. Repair as necessary. After repairs, go to step 15. If connections and circuit are okay, go to step 14.
9. Check for open or high resistance in Gray wire between FPS connector terminal "C" and AF ECU Blue connector C001 terminal No. 24. (Scheme 3) Check for poor connections at AF ECU. Repair as necessary. After repairs, go to step 15. If connections and circuit are okay, go to step 14.
10. Check for short to voltage in Red wire between FPS connector terminal "B" and AF ECU White/Clear connector C002 terminal No. 18. (Scheme 3) Repair as necessary. After repairs, go to step 15. If circuit is okay, go to step 14.
11. Repair open or high resistance in Black wire between FPS connector terminal "A" and splice S452 located in harness approximately 6" from High Pressure Lock-Off (HPL) connector at left side of trunk. After repairs, go to step 15.
12. Check for poor connections at FPS connector. Repair as necessary. After repairs, go to step 15. If connections are okay, go to next step.
13. Replace FPS. See FUEL TANK PRESSURE SENSOR under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. After repairs, go to step 15.
14. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See «ALTERNATE FUEL ENGINE CONTROL UNIT»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__alternate-fuel-engine-control-unit) under PROGRAMMING. After performing repairs and procedures, go to next step.
15. Using scan tool, clear DTCs from AF ECU and PCM. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step 2.

Problem may also be intermittent. See INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

DTC P1441: EVAP SYSTEM FLOW DURING NON-PURGE

Note. For circuit reference, see WIRING DIAGRAMS article.

This DTC tests for undesired intake manifold vacuum flow to Evaporative Emission (EVAP) system. PCM seals EVAP system by commanding EVAP purge valve OFF (closed) and EVAP vent valve ON (closed). PCM monitors Fuel Tank Pressure (FTP) sensor to determine if a vacuum is being drawn on EVAP system. If vacuum in EVAP system is more than a calibrated value within a calibrated time, DTC P1441 will set.

1. DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0440, P0442, P0446, P0452, or P0453 are not set.
2. Ignition voltage is 10-18 volts.
3. Barometric (BARO) pressure is more than 75 kPa.
4. Fuel level is 15-85 percent.
5. Engine Coolant Temperature (ECT) is 39-86°F (4-30°C).
6. Intake Air Temperature (IAT) is 39-86°F (4-30°C).
7. Start-up ECT and IAT are within 16°F (9°C) of each other.
8. Vehicle Speed Sensor (VSS) is less than 75 MPH.

DTC sets when PCM detects vacuum during a non-purge condition.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. If DTCs P0452 or P0453 are also set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If DTCs P0452 or P0453 are not set, go to next step.
3. Disconnect purge pipe from EVAP canister purge valve. Install a hand held vacuum gauge to EVAP canister purge valve purge port. Disconnect EVAP canister purge valve harness connector. Monitor vacuum on vacuum gauge. Start engine and allow engine to idle. Increase idle to 1200-1500 RPM. If vacuum gauge indicates an increase in vacuum, go to step 8 . If vacuum gauge does not indicate an increase in vacuum, go to next step.
4. Remove, and then reinstall fuel fill cap. Turn ignition on, engine off. Using scan tool, monitor Fuel Tank Pressure (FTP) sensor voltage. If scan tool indicates FTP voltage is near 1.5 volts, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) . If scan tool does not indicate FTP voltage is near 1.5 volts, go to next step.
5. If scan tool indicates FTP voltage is more than 4.3 volts, see «DTC P0453: FUEL TANK PRESSURE SENSOR CIRCUIT - HIGH VOLTAGE»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__dtc-p0453-fuel-tank-pressure-sensor) . If scan tool does not indicate FTP voltage is more than 4.3 volts, go to next step.
6. Check FTP connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 10 . If problem was not found, go to next step.
7. Replace fuel tank pressure sensor. After repairs, go to step 10 .
8. Inspect EVAP system for carbon release. If carbon release was found, clean carbon particles from system. After repairs, go to step 10 . If carbon release was not found, go to next step.
9. Replace EVAP canister purge valve. After repairs, go to next step.
10. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If DTC does not reset, go to next step.
11. Using scan tool, observe stored information. If any DTCs are displayed that have not been diagnosed, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) .

An intermittent condition could be caused by an improperly installed or damaged EVAP canister purge valve or a temporary blockage in EVAP canister purge valve. To repair a blockage in EVAP system perform fuel system cleaning.

DTC P1626: THEFT DETERRENT SYSTEM FUEL ENABLE SIGNAL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

Body Control Module (BCM) produces the theft deterrent fuel enable signal when ignition is on and the proper ignition code voltage value is detected. The Powertrain Control Module (PCM) monitors the fuel enable signal during crank. If the proper signal is present on the Class 2 Serial Data Circuit, the PCM enables fuel delivery in order to allow the engine to start. If the PCM determines that the fuel enable signal is not present or incorrect while the engine is running, DTC P1626 is set. The engine continues to start and run as long as DTC P1626 is stored.

1. Engine is running.

DTC sets when PCM has detected a loss of state of health serial data message from theft deterrent system.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. If DTC P1626 set as a current DTC, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If DTC P1626 is not set as a current DTC, see «DIAGNOSTIC AIDS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l) .

Disconnect and inspect PCM connector. Inspect for damaged pins, corrosion and loose wires. An intermittent problem can be caused by a poor connection, rubbed-through wire insulation or broken wire inside insulation. Reviewing FAILURE RECORDS vehicle mileage since diagnostic test last failed may help determine how often condition that caused DTC to be set occurs.

DTC P1630: THEFT DETERRENT SYSTEM LEARN MODE ACTIVE

Note. For circuit reference, see WIRING DIAGRAMS article.

Vehicle Theft Deterrent (VTD) system is incorporated within Body Control Module (BCM). If BCM has been replaced, password must be relearned. If PCM is replaced, replacement PCM should learn password within a few seconds after ignition is turned on. This is an information code indicating that PCM is ready to learn VTD password.

1. VTD system has allowed fuel delivery. PCM is in theft deterrent password learn mode.

DTC sets when PCM remains in theft deterrent password learn mode for more than 2 seconds.

Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, see PROGRAMMING THEFT DETERRENT SYSTEM COMPONENTS under PROGRAMMING.

A new replacement PCM will be in a functional state to learn password from BCM. If BCM is replaced, PCM must be placed in password learning mode to relearn a new password. Once learned, password becomes permanent information that remains with vehicle. Loss of PCM battery or ignition voltage will not affect the programmed password information.

An intermittent may be caused by poor connection, rubbed-through wire insulation or a broken wire inside insulation.

DTC P1631: THEFT DETERRENT FUEL ENABLE SIGNAL NOT CORRECT

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM controls fuel injector operation based on a Vehicle Theft Deterrent (VTD) password from vehicle Body Control Module (BCM). When ignition is first turned on, BCM sends a programmed theft deterrent password to PCM. PCM acknowledges password and responds to BCM that normal fuel injector operation will continue. If PCM detects an incorrect password, a theft deterrent system failure, or an attempted vehicle theft, DTC P1631 will set. Engine will not start as long as condition is present.

1. Ignition is on.

DTC sets when PCM detects an incorrect password from VTD system. Condition is present for less than one second.

Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, see PROGRAMMING THEFT DETERRENT SYSTEM COMPONENTS under PROGRAMMING.

DTC P1631 indicates that vehicle theft deterrent password that PCM has learned does not agree with password received from VTD system. This condition can occur if BCM has been replaced and PCM password learn function has not been enabled. If BCM has been replaced, password must be relearned.

An intermittent may be caused by poor connection, rubbed-through wire insulation or a broken wire inside insulation.

DTC P1632: THEFT DETERRENT FUEL DISABLE SIGNAL RECEIVED

Note. For circuit reference, see WIRING DIAGRAMS article.

PCM controls fuel injector operation based on a Vehicle Theft Deterrent (VTD) password from vehicle Body Control Module (BCM). When ignition is first turned on, BCM sends a programmed theft deterrent password to PCM. PCM acknowledges password and responds to BCM that normal fuel injector operation will continue. When starting engine, PCM looks for a password from BCM through Class 2 serial data circuit. If password is not recognized or not present, PCM will disable engine. If an incorrect or no password is received, this indicates that engine will start and stall immediately. Security indicator will flash on Instrument Panel Cluster (IPC) for approximately 4 seconds. If an incorrect or disable password is received more than 3 times, this indicates that engine is disabled for at least 10 minutes and that Security indicator will illuminate continuously on IPC for approximately 3 seconds then flash on IPC for 10 minutes. If PCM loses communication with BCM within same ignition cycle, vehicle will enter fail-enable mode and continue to run on following ignition cycles.

1. Ignition is cycled to on.

DTC sets when PCM receives a fuel disabled password from BCM or an undecided password was sent from BCM.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__powertrain-diagnostic-system-check-gasoline) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Install scan tool. Turn ignition on, engine off. Select DISPLAY DTCs function for PCM. If scan tool displays DTC P1626 or DTC P1631, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If scan tool does not display DTC P1626 or P1631, go to next step.
3. Perform programming theft deterrent system components procedure. See «PROGRAMMING THEFT DETERRENT SYSTEM COMPONENTS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__programming-theft-deterrent-system-components) under PROGRAMMING. Attempt to start engine. If engine starts and continues to run, go to step 8 . If engine does not start and continue to run, go to next step.
4. Display SECURITY DATA list for BCM. Observe PASSLOCK DATA VOLTAGE parameter. If scan tool indicates Passlock(tm) Data voltage is 0-5 volts, go to next step. If scan tool indicates Passlock(tm) Data voltage is not 0-5 volts, go to step 6 .
5. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 8 .
6. Invalid data will set a theft deterrent B-code. If any theft deterrent codes are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/pontiac/grand-am/v-1998-2005/remont/testing-diagnostics/#engine-controls-self-diagnostics-22l-24l__diagnostic-trouble-code-definitions) . If no other theft deterrent codes are set, go to next step.
7. Replace BCM. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. After repairs, go to next step.
8. Using scan tool, clear DTCs. Start engine. Idle engine at normal operating temperature. If DTC does not reset, system is okay.

Attempting to start vehicle by by-passing Passlock system or by substituting parts without performing programming theft deterrent system components procedure may set DTCs P1631 and P1632. See PROGRAMMING THEFT DETERRENT SYSTEM COMPONENTS under PROGRAMMING.

If no password is received, DTCs U1064 and P1632 may be set.

An intermittent may be caused by poor connection, rubbed-through wire insulation or a broken wire inside insulation.

See also:
• MODEL IDENTIFICATION
• DIAGNOSTIC PROCEDURE
• POWERTRAIN DIAGNOSTIC SYSTEM CHECK (GASOLINE)
• POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)
• DIAGNOSTIC TROUBLE CODE DEFINITIONS
• MIL INOPERATIVE
• MIL ON STEADY (GASOLINE)
• MIL INOPERATIVE (CNG)
• MIL ON STEADY (CNG)
• CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE
• PROGRAMMING THEFT DETERRENT SYSTEM COMPONENTS
• INSPECTION/MAINTENANCE SYSTEM CHECK (CNG)
• DTC P0420: TWC SYSTEM - LOW EFFICIENCY (2.2L)
• DRIVE CYCLE
• CONDITIONS FOR RUNNING
• DTC P0141: HO2S2 HEATER CIRCUIT
• P0105
• P0107
• P0108
• P0112
• P0113
• P0117
• P0118
• P0122
• P0123
• P0125
• P0128
• P0130
• P0131
• P0132
• P0133
• P0134
• P0137
• P0138
• P0140
• P0172
• P0201
• P0300
• P0300
• P0301
• P0301
• P0325
• P0325
• P0336
• P0340
• P0341
• P0440
• P0442
• P0446
• P0452
• P0453
• P0461
• P0462
• P0463
• P0480
• P0481
• P0502
• P0502
• P0503
• P0506
• P0507
• P0562
• P0563
• P0601 & P0603-P0607
• P0705
• P1133
• P1137
• P1138
• P1171
• P1336
• P1441
• P1626
• P1630
• P1631
• P1632
• CODE TYPES
• INTERMITTENT TROUBLE CODE DETERMINATION
• POWERTRAIN CONTROL MODULE REPROGRAMMING
• ALTERNATE FUEL ENGINE CONTROL UNIT