Engine Controls Self-Diagnostics - 3.1l & 3.4l Chevrolet Malibu V рестайлинг

MODEL IDENTIFICATION

Vehicle model is identified by fourth character of Vehicle Identification Number (VIN). VIN is stamped on metal pad on top of left end of instrument panel, near windshield. See MODEL IDENTIFICATION table.

MODEL 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 appropriate 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 3 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.

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 .

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.

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.

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.

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.

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. Powertrain diagnostic system check must be performed before using specific DTC testing procedure. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) .
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 1 or 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. (Scheme 1) DLC is located below left side of dash.

Scheme 1

POWERTRAIN DIAGNOSTIC SYSTEM CHECK

Note. Check for applicable Technical Service Bulletins (TSB) 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 under SYSTEM TESTS in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
2. Turn ignition on, engine off. Attempt to establish communication with specified class 2 modules. See «CLASS 2 MODULES»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table. 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 under SYSTEM TESTS in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
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 specified class 2 modules. See «CLASS 2 MODULES»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table. If DTCs are present, go to next step. If DTCs are not present, go to step 9 .
5. Using scan tool, select CAPTURE INFO to store powertrain DTC information. Go to next step.
6. If scan tool displays DTCs which begin with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE under SYSTEM TESTS in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If scan tool does not display DTCs which begin with "U", go to next step.
7. If scan tool displays DTC P0601 or P0602, go to «DTC P0601: PCM INTERNAL PROGRAM FAULT»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) or «DTC P0602: PCM NOT PROGRAMMED»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) under DIAGNOSTIC TESTS.
8. If scan tool displays DTC P0560 or P0620, see appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If scan tool does not display DTC P0560 or P0620, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) .
9. If customer's concern is with the automatic transmission, see appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS article. If customer's concern is not with the automatic transmission, go to next step.
10. If customer's concern is with Inspection/Maintenance (I/M) testing, go to «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) under INSPECTION/MAINTENANCE PROCEDURES. If customer's concern is driveability, see appropriate TROUBLE SHOOTING - NO CODES article.

CLASS 2 MODULES

ENGINE COOLING DIAGNOSTIC SYSTEM CHECK

1. Turn ignition off. Connect scan tool to Data Link Connector (DLC). DLC is located below left side of instrument panel, to right of steering column. Turn ignition on. If scan tool powers up, go to next step. If scan tool does not power up, go to SCAN TOOL DOES NOT POWER UP under SYSTEM TESTS in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
2. Turn ignition on. Try to establish scan tool communication with Instrument Panel Cluster (IPC) and PCM. If communication with IPC and PCM is established, go to next step. If communication with IPC and/or PCM is not established, go to SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE under SYSTEM TESTS in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
3. Select DISPLAY DTC function for PCM. Record all displayed DTCs and status of displayed DTCs. If any DTCs are displayed, go to next step. If no DTCs are displayed, repair cooling system as necessary.
4. If scan tool does not display any DTCs that begin with "U", go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool displays any DTCs that begin with "U", go to SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE under SYSTEM TESTS in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.

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. About 80 percent of driveability problems occur without setting DTCs. Sensors that are out of calibration will not set a DTC but will cause driveability problems.

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 non-existent 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 1 or Tech 2 scan tool. See scan tool operator's manual for additional information.

The following are Tech 1 or 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 over 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.

PCM LOCATION

On Alero, Grand Am and Malibu, PCM is located under left side of instrument panel, near steering column. On all other models, PCM is located in engine compartment. (Scheme 2)- (Scheme 4).

Scheme 2

Scheme 3

Scheme 4

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 , RESETTING GM OIL LIFE SYSTEM , INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE under INSPECTION/MAINTENANCE PROCEDURES and PROGRAMMING THEFT DETERRENT SYSTEM COMPONENTS .

CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE

Crankshaft position system variation compensating values are stored in PCM non-volatile memory after a learn procedure has been performed. If actual crankshaft position system variation is not within crankshaft position system variation compensating values stored in PCM, DTC P0300 may set. See DIAGNOSTIC AIDS under DTC P0300: ENGINE MISFIRE DETECTED.

Crankshaft position system variation learn procedure should be performed if any of the following conditions are true

1. DTC P1336 is set.
2. PCM has been replaced.
3. Engine has been replaced.
4. Crankshaft has been replaced.
5. Crankshaft harmonic balancer has been replaced.
6. Crankshaft position sensor has been replaced.

Note. The scan tool crankshaft position system variation learn function will be inhibited if engine coolant temperature is less than 158°F (70°C). Allow engine to warm to at least 158°F (70°C) before attempting crankshaft position system variation learn procedure.

The scan tool crankshaft position system variation learn function will be inhibited if any powertrain DTCs other than DTC P1336 are set before or during the crankshaft position system variation learn procedure. Diagnose and repair any DTCs set.

The crankshaft position system variation learn function will be inhibited if PCM detects a malfunction involving the camshaft position signal circuit, the 3X reference circuit, or the 24X reference circuit. If a malfunction has been indicated, perform one of the following tests diagnose system or sensor

1. «DTC P0336: CRANKSHAFT POSITION SENSOR CIRCUIT»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l)
2. «DTC P0341: CAMSHAFT POSITION (CMP) SENSOR CIRCUIT»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l)
3. «DTC P1374: CRANKSHAFT POSITION (CKP) HIGH-TO-LOW RESOLUTION FREQUENCY CORRELATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l)

The scan tool crankshaft position system variation learn function will not be enabled until engine coolant temperature reaches 158°F (70°C). Selecting crankshaft position system variation learn procedure on scan tool will command PCM to enable CKP system variation learn fuel cutoff and allow crankshaft position system variation compensating values to be stored in PCM. PCM must detect an engine speed of 5150 RPM during crankshaft position system variation learn procedure to store crankshaft position system variation compensating values and complete procedure.

1. Block drive wheels.
2. Ensure hood is closed.
3. Start engine and allow engine coolant temperature to reach at least 158° F (70°C).
4. Turn ignition off.
5. Using scan tool, select and enable CRANKSHAFT POSITION SYSTEM VARIATION LEARN PROCEDURE.
6. Set parking brake when instructed by scan tool.
7. Start engine.
8. Press and hold brake pedal firmly.
9. Ensure transaxle is in Park.
10. Slowly depress accelerator pedal until fuel cutoff is reached at 5150 and hold. Release accelerator pedal after second fuel cutoff has been reached.
11. Crankshaft position system variation compensating values are learned when engine RPM decreases back to idle.
12. Using scan tool, observe DTC status for DTC P1336.
13. If scan tool indicates that DTC P1336 ran and passed, crankshaft position system variation learn procedure is complete. If scan tool indicates that DTC P1336 failed or did not run, check for other DTCs. If no other DTCs are set, repeat crankshaft position system variation learn procedure as necessary.

With Driver Information Center

Press MODE button until light appears on Driver Information Center (DIC). Press and hold RESET button for 3 seconds. Oil life percentage should change to 100 percent.

Without Driver Information Center

Turn ignition on. Fully press and release accelerator pedal slowly 3 times within 5 seconds. If CHANGE OIL SOON light flashes, system is resetting. Turn ignition off. Start engine. Oil life will change to 100 percent. If CHANGE OIL SOON light comes back on, system has not reset. Repeat procedure.

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™ sensor data code and/or passwords on next ignition switch transition from OFF to CRANK position.
6. Start engine. Vehicle has now learned Passlock™ sensor data code and/or password.
7. Using scan tool, clear any DTCs if needed.

DRIVE CYCLES

See INSPECTION/MAINTENANCE SYSTEM CHECK .

Procedure

1. Perform «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. If DTC or driveability problems were repaired using powertrain diagnostic system check, go to step 3 . If no DTC or driveability problems 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»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . 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»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . 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.

Description

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.

Enable Criteria

1. Barometric Pressure (BARO) is more than 65 kPa.
2. Engine Coolant Temperature (ECT) is less than 86°F (30°C).
3. Intake Air Temperature (IAT) is less than 90°F (32°C).
4. Difference between IAT and ECT is less than 7°F.
5. Battery voltage is 10-18 volts.
6. Fuel level is 1/4-3/4.

1. Perform «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . After performing inspection/maintenance system check, go to next step.
2. Preprogram scan tool with vehicle information before ignition is turned on. Ensure vehicle meets conditions under «ENABLE CRITERIA»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__enable-criteria) . Turn off all accessories, such as A/C, blower fan, etc. Set vehicle parking brake. Ensure transmission is in Park. Start engine. Allow engine to idle for 2 minutes. Go to next step.
3. Accelerate at part throttle to 55 MPH 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 with this speed maintained for one additional minute. Perform 4 decelerations of 25 seconds each from 45 MPH while the following criteria is maintained: Throttle is closed. No brake application on either M/T or A/T. No clutch actuation on M/T. No manual downshift. Vehicle speed remains more than 25 MPH. After each deceleration period, vehicle is returned to 45 MPH under part throttle acceleration and speed is maintained for 15 seconds. When complete, go to next step.
5. Accelerate at part throttle to 45-55 MPH. Maintain this speed for 2 minutes. Decelerate to zero MPH. Allow engine to idle for 2 minutes while the following criteria is maintained: Service brake depressed. A/T in Drive. M/T in neutral with clutch pedal depressed. When complete, 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, see INSPECTION/MAINTENANCE SET PROCEDURE for indicated systems.
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»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__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.

1. Barometric Pressure (BARO) is more than 65 kPa.
2. Engine coolant is 203-212°F (95-100°C).
3. Intake Air Temperature (IAT) is 59-167°F (-15-75°C).
4. Engine is in closed loop.
5. Engine has run for 6-8 minutes off idle.
6. Battery voltage is 10-18 volts.

1. Perform «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . After performing inspection/maintenance system check, go to next step.
2. Ensure vehicle is operating within enable criteria. 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 zero MPH and allow engine to idle for 2 minutes while service brake is depressed, A/T in Drive and M/T in neutral with clutch pedal 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»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__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: CATALYST SYSTEM LOW EFFICIENCY»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) 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»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) .
5. Using scan tool, check for DTCs. If scan tool indicates any DTCs are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not indicate any DTCs are set, system is okay.

If status does not update, repeat this test until I/M SYSTEM STATUS updates to YES. PCM runs a maximum of 6 tests per trip until CATALYST SYSTEM STATUS updates to YES.

I/M SYSTEM STATUS does not indicate whether 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 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, emission related DTC portion of 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 an emission related DTC fails second time, or when 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 test is running. For example, changes in engine load, such as a cooling fan or an A/C compressor clutch turning on, may cause the 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 should satisfy enable criteria necessary to execute I/M readiness diagnostics for the EGR system. Test may be used to set I/M SYSTEM STATUS indicators to YES.

1. Barometric Pressure (BARO) is more than 65 kPa.
2. Engine Coolant Temperature (ECT) is 176-230°F (80-110°C).
3. Intake Air Temperature (IAT) is less than 149°F (65°C).

1. Perform «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . After performing inspection/maintenance system check, go to next step.
2. Ensure vehicle is within enable criteria. Turn off all of accessories. Start engine and allow to idle. Accelerate at part throttle to 45 MPH and maintain speed for one minute. Perform 4 decelerations of 25 seconds each from 45 MPH while following criteria is maintained: Throttle is closed No brake application on either manual or automatic transmission No clutch actuation on a manual transmission No manual downshift Vehicle speed remains more than 25 MPH. After each deceleration period, vehicle is returned to 45 MPH under part throttle acceleration and speed is maintained for 15 seconds. Using scan tool, observe I/M SYSTEM STATUS display. If EGR system status updates to YES, go to step 5 . If EGR 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»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__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 P0401, P0404, P0405 and P1404 have run. For those DTCs that have not run, see CODE ENABLE CRITERIA in 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 EGR system status updated to YES, go to next step. If EVAP system status did not update to YES, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) .
5. Using scan tool, check for DTCs. If scan tool indicates any DTCs are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not indicate any DTCs are set, system is okay.

Control module only runs EGR active tests during a gradual deceleration with a closed throttle and a vehicle speed more than 25 MPH. Several deceleration cycles may be necessary in order to accumulate a sufficient number of EGR flow samples. Procedure outlined in procedure is for a clear, flat road. If procedure is performed on a road with a slight down hill grade, test may acquire necessary sample counters in one or 2 decel trips. If test is interrupted during procedure, you may need to take more than 3 deceleration cycles to complete test. 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 a decision was made. When all of 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 of the 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 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 an emission related DTC fails second time, or when all of 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 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.

Purpose of this test is to satisfy enable criteria necessary to execute I/M readiness diagnostics for Evaporative Emission (EVAP) system. Test may be used to set I/M SYSTEM STATUS indicators to YES. Service Bay Tests are included on scan tool for some systems depending upon vehicle make and model. Test is designed to allow EVAP diagnostic tests to run in service bay conditions. Ensure vehicle meets requirements listed in enable criteria before performing either EVAP system test. Failure to meet necessary requirements may produce inaccurate test results.

Non Scan Tool Service Bay Test

1. Barometric Pressure (BARO) is more than 75 kPa.
2. Fuel level is 15-85 percent.
3. Battery voltage is 10-18 volts.
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. Difference between ECT and IAT is less than 14°F (8°C).

Scan Tool Service Bay Test

1. BARO is more than 65 kPa.
2. Engine Coolant Temperature (ECT) is less than 158°F (70°C).
3. Fuel level is 25-75 percent.
4. Battery voltage is 10-18 volts.

1. Perform «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . After performing inspection/maintenance system check, go to next step.
2. Using scan tool, select SPECIAL FUNCTIONS. Determine if vehicle is equipped with a Service Bay Test for EVAP system. If vehicle is 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 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 repairs, see «INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) .
5. Ensure vehicle is within enable criteria. Turn off all of accessories. Once engine is started, DO NOT turn engine off for remainder of procedure until test is complete. Start and idle engine. Operate vehicle in following manner: Accelerate at part throttle to 45 MPH. Maintain speed until engine reaches operating temperature (may be up to 8-10 minutes). 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 updates to YES, go to step 8 . If EVAP SYSTEM STATUS does 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»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__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 in 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»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) .
8. Using scan tool, check for DTCs. If scan tool indicates any DTCs are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not indicate any DTCs are set, system is okay.

Extreme high or low ambient temperatures may prevent EVAP system tests from initiating. Performing a visual inspection prior to running EVAP Service Bay Test may prevent having to repeat test. A loose fuel cap may cause a Service Bay Test to abort or fail and prevent I/M SYSTEM STATUS 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 a decision was made. 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, emission related DTC portion of 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 an emission related DTC fails second time, or when 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 test is running. For example, changes in engine load, such as a cooling fan or an A/C compressor clutch turning on, may cause the 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 oxygen sensor (O2S, HO2S) system. Test may be used to set I/M SYSTEM STATUS to YES. Ensure vehicle meets requirements listed in enable criteria before performing this test. Failure to meet necessary requirements may produce inaccurate test results.

1. Engine Coolant Temperature (ECT) is more than 176°F (80°C).
2. Engine is running in closed loop.
3. Engine has been running for more than 4 minutes.
4. Battery voltage is 10-18 volts.

1. Perform «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . After performing inspection/maintenance system check, go to next step.
2. Verify vehicle is within enable criteria. Turn off all accessories. Start and idle engine. Accelerate at part throttle to 45-55 MPH. Maintain this speed for 6 minutes or until I/M SYSTEM STATUS updates to YES. M/T may require operation in 4th or 5th gear. Using scan tool, review I/M SYSTEM STATUS display. If HO2S SYSTEM STATUS update to YES, go to step 5 . If HO2S 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»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__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, P1133 and P1134 have run. For those DTCs that have not run, see CODE ENABLE CRITERIA in 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 HO2S SYSTEM STATUS updated to YES, go to next step. If HO2S SYSTEM STATUS did not update to YES, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) .
5. Using scan tool, check for DTCs. If scan tool indicates any DTCs are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not indicate any DTCs are set, system is okay.

If status does not update, repeat this test until I/M SYSTEM STATUS updates to YES.

I/M SYSTEM STATUS does not indicate whether 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 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, emission related DTC portion of 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 an emission related DTC fails second time, or when 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 test is running. For example, changes in engine load, such as a cooling fan or an A/C compressor clutch turning on, may cause the 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 (HO2S) system. The test may be used to set I/M SYSTEM STATUS to YES. Ensure vehicle meets enable criteria before performing this test. Failure to meet necessary requirements may produce inaccurate test results.

1. Engine Coolant Temperature (ECT) is less than 90°F (32°C).
2. Intake Air Temperature (IAT) is less than 90°F (32°C).
3. Difference between IAT and ECT is less than 7°F.
4. Battery voltage is 10-18 volts.

1. Perform «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . After performing inspection/maintenance system check, go to next step.
2. Preprogram scan tool with vehicle information before ignition is turned on. Verify vehicle is within enable criteria. Set vehicle parking brake. Ensure transmission is in Park or Neutral. Turn off all of accessories. Start the engine. Allow engine to idle for 2 minutes or until I/M SYSTEM STATUS indicator updates to YES. Using scan tool, observe I/M SYSTEM STATUS display. If HO2S HEATER SYSTEM STATUS updated to YES, go to step 5 . If HO2S HEATER 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»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__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 P0135 and P0141 have run. For those DTCs that have not run, see CODE ENABLE CRITERIA in 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 HO2S HEATER SYSTEM STATUS updated to YES, go to next step. If HO2S HEATER SYSTEM STATUS did not update to YES, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) .
5. Using scan tool, check for DTCs. If scan tool indicates any DTCs are set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not indicate any DTCs are set, system is okay.

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 the 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 a decision was made. 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, emission related DTC portion of 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 an emission related DTC fails second time, or when 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 test is running. For example, changes in engine load, such as a cooling fan or an A/C compressor clutch turning on, may cause the 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.

SUMMARY

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 appropriate TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, ENGINE STALLS, etc.).

DIAGNOSTIC TROUBLE CODE DEFINITIONS

Note. Use of Tech 1 or Tech 2 scan tool is required to retrieve DTCs. Refer to user reference manual supplied with scan tool.

DIAGNOSTIC TROUBLE CODE INDEX

MIL Inoperative

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) 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, go to step 9.
3. Check fuse that supplies voltage to MIL. See «MIL SUPPLY VOLTAGE CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table. If fuse is open, go to step 7. If fuse is okay, go to next step.
4. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Turn ignition on. Connect fused jumper wire between ground and PCM harness connector C2 terminal No. 5 (Brown/White wire). (Scheme 5)or (Scheme 6). Observe MIL. If MIL illuminates, go to step 15. If MIL does not illuminate, go to next step.
5. Turn ignition off. Remove Instrument Panel Cluster (IPC). See appropriate ANALOG INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. Turn ignition on. Connect a test light between ground and appropriate IPC harness connector terminal. See «MIL SUPPLY VOLTAGE CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table. If test light illuminates, go to next step. If test light does not illuminate, go to step 8.
6. Check for open or high resistance in Brown/White wire between PCM harness connector C2 terminal No. 46 and appropriate IPC harness connector terminal. See «MIL CONTROL CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table. Repair circuit as necessary, then perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. If circuit is okay, go to step 14.
7. Repair short to ground in MIL supply voltage circuit. After repair, perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
8. Repair open in MIL supply voltage circuit. After repair, perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
9. Check PCM fuse and ignition 1 main fuse. See WIRING DIAGRAMS article. If either fuse is open, go to step 12. If both fuses are okay, go to next step.
10. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Connect a test light between ground and all ignition positive circuits. See WIRING DIAGRAMS article. If test light illuminates on all ignition positive circuits, go to next step. If test light does not illuminate on all ignition positive circuits, go to step 12.
11. Connect test light between ground and PCM harness connector C1 terminal No. 20 (Orange wire). (Scheme 5)or (Scheme 6). If test light illuminates, go to step 13. If test light does not illuminate, go to next step.
12. Repair open or short to ground in Orange wire or in ignition feed circuits. See WIRING DIAGRAMS article. After repairs, perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
13. Check for a poor PCM ground or a poor PCM ground connection. See WIRING DIAGRAMS article. If a problem is found, repair as necessary, then perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. If a problem is not found, go to step 15.
14. Check for poor connections at IPC. If a problem is found, repair as necessary, then perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. If a problem is not found, go to step 16.
15. Check for poor connections at PCM. If a problem is found, repair as necessary, then perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. If a problem is not found, go to step 17.
16. Replace IPC. After repair, perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.
17. Replace PCM. After repair, perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM.

MIL SUPPLY VOLTAGE CIRCUIT IDENTIFICATION

MIL CONTROL CIRCUIT IDENTIFICATION

Scheme 5

Scheme 6

Scheme 7

Scheme 8

Scheme 9

MIL Always On

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, check for DTCs. If any DTCs are set, perform appropriate test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If no DTCs are set, go to next step.
3. Turn ignition off. Observe MIL. If MIL is on, go to step 6 . If MIL is off, go to next step.
4. Turn ignition on. Using scan tool, command MIL on and off several times. If MIL turns on and off with each command, no problem is indicated at this time. If MIL does not turn on and off with each command, go to next step.
5. Repair short to ground in MIL control circuit (Brown/White wire) between PCM harness connector C2 terminal No. 46 and appropriate IPC harness connector terminal. See «MIL CONTROL CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table. After repairs, go to step 7 .
6. Repair short to voltage in MIL control circuit (Brown/White wire) between PCM harness connector C2 terminal No. 46 and appropriate IPC harness connector terminal. See «MIL CONTROL CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table. After repairs, go to next step.
7. Turn ignition on. Using scan tool, command MIL on and off several times. If MIL turns on and off with each command, perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. If MIL does not turn on and off with each command, go to step 2 .

DIAGNOSTIC TESTS

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

Note. If PCM is replaced, NEW PCM must be programmed using special manufacturer's equipment.

Circuit Description

Heated Oxygen Sensors (HO2S) are used to minimize the amount of time required to enter closed loop fuel control and to allow accurate catalyst monitoring. PCM controls HO2S heater operation by grounding HO2S heater control circuit. PCM has the ability to measure the amount of current drawn on HO2S heater control circuit.

Code Enable Criteria

PCM will run diagnostic for this DTC when engine is running. DTC P0300 will set when PCM detects that HO2S heater control circuit current is greater than the capacity of PCM internal driver for more than 20 seconds.

Diagnostic Procedure (Alero, Grand Am, Impala, Malibu & Monte Carlo)

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Start engine and warm to normal operating temperature. Allow engine idle to stabilize for at least one minute. Using scan tool, monitor O2 HEATER CURRENT. If scan tool displays.25-.85 amp, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM. If scan tool does not display.25-.85 amp, go to next step.
3. Check ERLS fuse (10-amp) located in underhood fuse block. If fuse is open, go to step 11. If fuse is okay, go to next step.
4. Turn engine off. Turn ignition on. Disconnect HO2S 1 harness connector. (Scheme 10) Connect a test light between ground and ignition 1 voltage circuit (Brown wire) at HO2S 1 harness connector terminal "D". If test light illuminates, go to next step. If test light does not illuminate, go to step 7.
5. Connect test light between ignition 1 voltage circuit (Brown wire) at HO2S 1 harness connector terminal "D" and HO2S 1 heater low control circuit (Black/White wire) at HO2S 1 harness connector terminal "C". Start engine. If test light illuminates, go to step 9. If test light does not illuminate, go to next step.
6. Turn ignition off. Connect test light between ground and HO2S 1 heater low control circuit (Black/White wire) at HO2S 1 harness connector terminal "C". Start engine. If test light illuminates, go to step 8. If test light does not illuminate, go to step 12.
7. Repair open in ignition 1 voltage circuit (Brown wire) between HO2S 1 and underhood fuse block. See WIRING DIAGRAMS article. After repairs, go to step 14.
8. Repair short to voltage in HO2S 1 heater low control circuit (Black/White wire) between HO2S 1 harness connector terminal "C" and PCM harness connector C2 terminal No. 37. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). After repairs, go to step 14.
9. Check for poor connections or poor terminal tension at HO2S 1 harness connector. If a poor connection is found, replace terminals. After repairs, go to step 14. If no poor connections are found, go to next step.
10. Replace HO2S 1. After repairs, go to step 14.
11. Repair short to ground in ignition 1 voltage circuit (Brown wire) between HO2S 1 and underhood fuse block. Replace fuse. See WIRING DIAGRAMS article. After repairs, go to step 14.
12. Check for poor connections or poor terminal tension at PCM harness connector. If a problem is found, repair as necessary. After repairs, go to step 14. If a problem is not found, go to next step.
13. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
14. Start engine and warm to normal operating temperature. Allow engine idle to stabilize for at least one minute. Using scan tool, monitor O2 HEATER CURRENT. If scan tool displays.25-.85 amp, go to next step. If scan tool does not display.25-.85 amp, go to step 2.
15. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Scheme 10

Diagnostic Procedure (Century & Grand Prix)

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Start engine and warm to normal operating temperature. Allow engine idle to stabilize for at least one minute. Using scan tool, monitor O2 HEATER CURRENT. If scan tool displays.25-.85 amp, go to «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM. If scan tool does not display.25-.85 amp, go to next step.
3. On Century, check OXY SEN fuse (15-amp) located in underhood fuse block. On Grand Prix, check IGN1-UH fuse (15-amp) located in underhood fuse block. On all models, if fuse is open, go to step 11. If fuse is okay, go to next step.
4. Turn engine off. Turn ignition on. Disconnect HO2S 1 harness connector. (Scheme 11) Connect a test light between ground and ignition 1 voltage circuit (Pink wire) at HO2S 1 harness connector terminal "D". If test light illuminates, go to next step. If test light does not illuminate, go to step 7.
5. Connect test light between ignition 1 voltage circuit (Pink wire) at HO2S 1 harness connector terminal "D" and HO2S 1 heater low control circuit (Black/White wire) at HO2S 1 harness connector terminal "C". Start engine. If test light illuminates, go to step 9. If test light does not illuminate, go to next step.
6. Turn ignition off. Connect test light between ground and HO2S 1 heater low control circuit (Black/White wire) at HO2S 1 harness connector terminal "C". Start engine. If test light illuminates, go to step 8. If test light does not illuminate, go to step 12.
7. Repair open in ignition 1 voltage circuit (Pink wire) between HO2S 1 harness connector terminal "D" and underhood fuse block. See WIRING DIAGRAMS article. After repairs, go to step 14.
8. Repair short to voltage in HO2S 1 heater low control circuit (Black/White wire) between HO2S 1 harness connector terminal "C" and PCM harness connector C2 terminal No. 37. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). For PCM terminal identification (Scheme 5)or (Scheme 6). After repairs, go to step 14.
9. Check for poor connections or poor terminal tension at HO2S 1 harness connector. If a poor connection is found, replace terminals. After repairs, go to step 14. If no poor connections are found, go to next step.
10. Replace HO2S 1. After repairs, go to step 14.
11. Repair short to ground in ignition 1 voltage circuit (Pink wire) between HO2S 1 and underhood fuse block. See WIRING DIAGRAMS article. After repairs, go to step 14.
12. Check for poor connections or poor terminal tension at PCM harness connector. 1If a problem is found, repair as necessary. After repairs, go to step 14. If a problem is not found, go to next step.
13. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
14. Start engine and warm to normal operating temperature. Allow engine idle to stabilize for at least one minute. Using scan tool, monitor O2 HEATER CURRENT. If scan tool displays.25-.85 amp, go to next step. If scan tool does not display.25-.85 amp, go to step 2.
15. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and wait at least 20 seconds. If DTC P0030 runs and passes, go to next step. If DTC P0030 does not run and pass, go to step 2.
16. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Scheme 11

Mass Airflow (MAF) sensor is an airflow meter that measures the amount of air entering the engine. PCM uses the MAF sensor signal in order to provide the correct fuel delivery for a wide range of engine speeds and loads. A small quantity of air entering the engine indicates deceleration or idle. A large quantity of air entering the engine indicates an acceleration or high load situation.

MAF sensor has an ignition 1 voltage circuit, a ground circuit and a signal circuit. PCM applies a voltage to the sensor on the signal circuit. MAF sensor uses the voltage in order to produce a frequency based on inlet air flow through the sensor bore. PCM uses the barometric pressure, air density, manifold pressure, throttle position, and the engine RPM in order to calculate a predicted MAF value. The PCM compares the actual MAF sensor signal to the predicted MAF value in order to determine if the signal is stuck based on a lack of variation, or is too low or too high for a given operating condition. DTC P0101 will set if the actual MAF sensor signal is not within a predetermined range of the calculated MAF value.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0102, P0103, P0107, P0108, P0121, P0122, P0123, P0401, P0404, P0405, P0440, P0442, P0446, P1404, or P1441 are not set.
2. Engine is running.
3. Ignition 1 signal voltage is 9-18 volts.
4. TP sensor angle is no more than 25 percent.
5. TP sensor is steady for more than 1.5 seconds.
6. MAP sensor value is no more than 63 kPa.
7. MAP sensor is steady for more than 3 seconds.

DTC will set when actual MAF sensor signal is not within a predetermined range of calculated MAF value.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, check for DTCs. If any other DTCs are set, diagnose those DTCs first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If no other DTCs are set, go to next step.
3. Turn ignition on. Using scan tool, review FREEZE FRAME data and note parameters. Turn ignition off for 30 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Select SPECIFIC DTC function. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed this ignition cycle, go to «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
4. Let engine idle at normal operating temperature. Using scan tool, observe MAP sensor voltage. If MAP sensor voltage is 0.8-4.0 volts, go to next step. If MAP sensor voltage is not 0.8-4.0 volts, diagnose and repair MAP sensor or circuit. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article.
5. Turn ignition off. Check for objects blocking MAF sensor air inlet screen. (Scheme 12), (Scheme 13) or (Scheme 14). Check for a plugged or collapsed intake air duct or dirty air filter element. Inspect for vacuum leaks in the following components: intake manifold, throttle body, EGR valve flange and pipe, MAF sensor seal, MAP sensor seal, EVAP canister purge valve seal, fuel meter body seal, crankcase ventilation system, brake booster system and air induction system. After repairs, go to step 23. If no problems are found, go to next step.
6. Turn ignition off. Disconnect MAP sensor vacuum hose. (Scheme 10)or (Scheme 15). Connect a hand vacuum pump to MAP sensor. Turn ignition on. Using scan tool, observe MAP sensor value while slowly applying vacuum to MAP sensor (one in. Hg at a time, up to 20 in. Hg). Each one in. Hg of vacuum should result in a 3-4 kPa drop in MAP sensor value on scan tool. If scan tool value changes smoothly through entire range, go to next step. If scan tool value does not change smoothly through entire range, diagnose and repair MAP sensor or circuit. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article.
7. Using hand vacuum pump, apply 20 in. Hg of vacuum to MAP sensor. Using scan tool, observe MAP sensor value. If scan tool displays 34 kPa, go to next step. If scan tool does not display 34 kPa, diagnose and repair MAP sensor or circuit. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article.
8. Disconnect vacuum pump from MAP sensor. Using scan tool, observe MAP sensor value. If scan tool displays original value that was observed in step 6, go to next step. If scan tool does not display original value that was observed in step 6, diagnose and repair MAP sensor or circuit. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article.
9. Using scan tool, observe TP sensor angle parameter. Slowly open throttle to wide open throttle. If scan tool indicates TP sensor angle changed smoothly and completely from 0-100 percent, go to next step. If scan tool does not indicate TP sensor angle changed smoothly and completely from 0-100 percent, diagnose using DTC P0121. See «DTC P0121: TP SENSOR PERFORMANCE»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
10. Turn ignition off. Disconnect MAF sensor harness connector. Turn ignition on. Measure voltage between ground and signal circuit (Yellow wire) at MAF sensor harness connector terminal "A". If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step 12.
11. Connect a test light between ignition 1 voltage circuit (Pink wire) at MAF sensor harness connector terminal "C" and ground circuit (Black/White wire) at MAF sensor harness connector terminal "B". If test light illuminates, go to step 19. If test light does not illuminate, go to step 14.
12. If voltage is less than 4.5 volts, go to step 15. If voltage is 4.5 volts or more, go to next step.
13. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Turn ignition on. Measure voltage between ground and signal circuit (Yellow wire) at MAF sensor harness connector terminal "A". If voltage is about zero volts, go to step 22. If voltage is not about zero volts, go to step 18.
14. Connect test light between ground and ignition 1 voltage circuit (Pink wire) at MAF sensor harness connector terminal "C". If test light illuminates, go to step 16. If test light does not illuminate, go to step 17.
15. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Check for open, high resistance, short to ground or short to sensor ground in signal circuit (Yellow wire) between MAF sensor harness connector terminal "A" and PCM C1 harness connector terminal No. 69. (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 23. If circuit is okay, go to step 20.
16. Repair open or high resistance in MAF sensor ground circuit (Black/White wire) between MAF sensor harness connector terminal "B" and ground point located near starter. After repairs, go to step 23.
17. Repair open or short to ground in ignition 1 voltage circuit (Pink wire) between MAF sensor harness connector terminal "C" and underhood fuse block. See WIRING DIAGRAMS article. After repairs, go to step 23.
18. Repair short to voltage in signal circuit (Yellow wire) between MAF sensor harness connector terminal "A" and PCM C1 harness connector terminal No. 69. After repairs, go to step 23.
19. Inspect MAF sensor harness connector for poor connections. Repair connector as necessary, then go to step 23. If connector is okay, go to step 21.
20. Inspect PCM sensor harness connectors for poor connections. Repair connector(s) as necessary, then go to step 23. If connectors are okay, go to step 22.
21. Replace MAF sensor. After repairs, go to step 23.
22. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
23. Using scan tool, review FREEZE FRAME data and note parameters. Turn ignition off for 30 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
24. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Scheme 12

Scheme 13

Scheme 14

Scheme 15

1. Ensure MAF sensor harness is not routed too close to any secondary ignition wires or coils, solenoids, relays or motors. Ensure throttle plate is not sticking and no excessive deposits exist on throttle plate or in throttle bore. Any unmetered air entering engine may cause this DTC to set. Ensure oil dipstick is fully seated and oil fill cap is secure.
2. A wide open throttle acceleration from a stop should cause the MAF sensor value displayed on a scan tool to increase from about 4-7 g/s at idle to 100 g/s or more at the time of the 1-2 shift. If MAF sensor value is not as specified, check for a restriction in intake air duct.
3. Barometric pressure value that is used to calculate predicted MAF value is based on MAP sensor reading at key ON. A skewed MAP sensor will cause the calculated mass airflow value to be inaccurate. The value shown for the MAP sensor display varies with the altitude. With the ignition ON and the engine OFF, 103 kPa is the approximate value displayed at or near sea level. The value decreases by approximately 3 kPa for every 1,000 feet of altitude.
4. Inspect for an unresponsive MAP sensor due to the following conditions: poor vacuum connections, damaged vacuum source, damaged vacuum hoses or any unmetered air into intake manifold.

Mass Airflow (MAF) sensor is an airflow meter that measures the amount of air entering engine. PCM uses MAF sensor signal to provide correct fuel delivery for a wide range of engine speeds and loads. A small quantity of air entering engine indicates deceleration or idle. A large quantity of air entering engine indicates an acceleration or high load situation.

MAF sensor has an ignition 1 voltage circuit, a ground circuit and a signal circuit. PCM applies a voltage to MAF sensor on the signal circuit. MAF sensor uses this voltage in order to produce a frequency based on inlet air flow through MAF sensor bore. Frequency will vary within a range of around 2000 Hertz (Hz) at idle to about 10,000 Hz at maximum engine load. DTC P0102 will set if PCM detects a frequency signal lower than the possible range of a normally operating MAF sensor.

PCM will run diagnostic for this DTC under the following conditions

1. Engine is running.
2. IAC position parameter more than 2 counts.
3. System voltage is greater than 8 volts.

DTC will set when MAF signal frequency is less than 1200 Hz for more than .5 second.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Start engine and let it idle. Using scan tool, observe MAF sensor frequency parameter. If scan tool displays less than 1200 Hz, go step 4. If scan tool displays 1200 Hz or more, go to next step.
3. Turn ignition on. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Select SPECIFIC DTC function, and then enter this DTC. If scan tool indicates FAILED THIS IGN, go to next step. If scan tool does not indicate FAILED THIS IGN, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
4. On Century, check ENG EMIS fuse (10-amp). On Grand Prix, check IGN1-UH fuse (15-amp). On Malibu, check PCM IGN fuse No. 39 (10-amp). On all models, fuses are located in underhood fuse block. If fuse is open, go to step 14. If fuse is okay, go to next step.
5. Turn ignition off. Disconnect MAF sensor harness connector. (Scheme 12), (Scheme 13) or (Scheme 14). Turn ignition on. Measure voltage between ground and signal circuit (Yellow wire) at MAF sensor harness connector terminal "A". If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step 8.
6. Turn ignition off. Connect a 3-amp fused jumper wire between ground and signal circuit (Yellow wire) at MAF sensor harness connector terminal "A". Start engine. If any additional DTCs set, go to step 16. If no additional DTCs set, go to next step.
7. Turn ignition off. Connect a test light between ignition 1 voltage circuit (Pink wire) at MAF sensor harness connector terminal "C" and ground circuit (Black/White wire) at MAF sensor harness connector terminal "B". If test light illuminates, go to step 18. If test light does not illuminate, go to step 11.
8. If voltage is less than 4.5 volts, go to step 10. If voltage is 4.5 volts or more, go to next step.
9. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Turn ignition on. Measure voltage between ground and signal circuit (Yellow wire) at MAF sensor harness connector terminal "A". If voltage is about zero volts, go to step 12. If voltage is not about zero volts, go to step 15.
10. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Check for open, high resistance, short to ground or short to sensor ground in signal circuit (Yellow wire) between MAF sensor harness connector terminal "A" and PCM C1 harness connector terminal No. 69. (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 22. If circuit is okay, go to step 12.
11. Connect a test light between ground and ignition 1 voltage circuit (Pink wire) at MAF sensor harness connector terminal "C". If test light illuminates, go to step 13. If test light does not illuminate, go to step 14.
12. Turn ignition off. Check continuity between signal circuit (Yellow wire) at PCM C1 harness connector terminal No. 69 and all other circuits at both PCM harness connectors. If continuity exists, between any other circuit, go to step 17. If continuity does not exist between any other circuit, go to step 19.
13. Repair open or high resistance in ground circuit (Black/White wire) between MAF sensor harness connector terminal "B" and ground point located near starter. See WIRING DIAGRAMS article. After repairs, go to step 22.
14. Repair open or short to ground in ignition 1 voltage circuit (Pink wire) between MAF sensor and underhood fuse block. See WIRING DIAGRAMS article. After repairs, go to step 22.
15. Repair short to voltage in signal circuit (Yellow wire) between MAF sensor harness connector terminal "A" and PCM C1 harness connector terminal No. 69. After repairs, go to step 22.
16. Repair short between MAF signal circuit and circuit for which DTC was set. See WIRING DIAGRAMS article. After repairs, go to step 22.
17. Repair short between circuits. See WIRING DIAGRAMS article. After repairs, go to step 22.
18. Inspect MAF sensor harness connector for poor connections. Repair connector as necessary, then go to step 22. If connector is okay, go to step 20.
19. Inspect PCM harness connectors for poor connections. Repair connector(s) as necessary, then go to step 22. If connectors are okay, go to step 21.
20. Replace MAF sensor. After repairs, go to step 22.
21. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
22. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
23. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Ensure MAF sensor wiring harness is not routed too close to secondary ignition wires or coils, or any solenoids, relays or motors. A low minimum air rate may cause this DTC to set during deceleration. Check for plugged or collapsed intake air duct or dirty air filter element, objects blocking MAF sensor air inlet screen, or throttle bore and throttle plate coking.

A wide open throttle acceleration from a stop should cause the MAF parameter on scan tool to increase from about 4-7 g/s at idle to about 100 g/s or more at the time of the 1-2 shift. If parameter is not as specified, check for a restriction. Any unmetered air entering engine may cause this DTC to set. Check for vacuum leaks anywhere downstream of MAF sensor.

Mass Airflow (MAF) sensor is an air flow meter that measures amount of air entering engine. PCM uses MAF sensor frequency signal to provide correct fuel delivery for a wide range of engine speeds and loads. A small quantity of air entering engine indicates deceleration or idle. A large quantity of air entering engine indicates an acceleration or high load situation. MAF sensor has an ignition 1 voltage circuit, a ground circuit and a signal circuit.

PCM applies a voltage to MAF sensor on the signal circuit. MAF sensor uses this voltage in order to produce a frequency based on inlet air flow through sensor bore. Frequency will vary within a range of around 2000 Hertz (Hz) at idle to about 10,000 Hz at maximum engine load.

PCM will run diagnostic for this DTC under the following conditions

1. Engine is running.
2. IAC position parameter is more than 2 counts.
3. System voltage is greater than 8 volts.

DTC will set when MAF signal frequency is more than 11,500 Hz for more than .5 second.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Select SPECIFIC DTC function then enter this DTC. If scan tool indicates FAILED THIS IGN, go to next step. If scan tool does not indicate FAILED THIS IGN, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
3. Turn ignition off. Disconnect MAF sensor harness connector. (Scheme 12), (Scheme 13) or (Scheme 14). Start engine. Using scan tool, monitor MAF frequency. If frequency is zero Hz, go to step 5. If frequency is not zero Hz, go to next step.
4. Check for incorrect routing of MAF sensor wiring harness. Ensure harness is not near any secondary ignition coils or wires, or any solenoids, relays or motors. Reroute wiring harness as necessary. After repairs, go to step 9. If no problems are found, go to step 6.
5. Inspect MAF sensor harness connector for poor connections. Repair connector as necessary, then go to step 9. If connector is okay, go to step 7.
6. Inspect PCM harness connectors for poor connections. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Repair as necessary, then go to step 9. If connectors are okay, go to step 8.
7. Replace MAF sensor. After repairs, go to step 9.
8. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
9. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
10. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Water entering air intake system that reaches MAF sensor could cause this DTC to set. The water rapidly cools hot sensing elements in MAF sensor causing a false indication of excessive air flow. Check for evidence of water intrusion in air injection system and air induction system. A poor connection in ignition 1 voltage circuit at MAF sensor can cause this DTC to set.

Manifold Absolute Pressure (MAP) sensor responds to pressure changes in the intake manifold. Theses pressure changes occur based on engine load. MAP sensor has a 5-volt reference circuit, a low reference circuit and a signal circuit. PCM supplies 5 volts to MAP sensor on 5-volt reference circuit and a ground on low reference circuit. MAP sensor provides a signal to PCM on signal circuit which is relative to pressure changes in the intake 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 is on with engine off or at Wide Open Throttle (WOT). Certain models will also use MAP sensor in order to determine Barometric Pressure (BARO). This occurs when ignition switch 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. If PCM detects a MAP sensor signal voltage that is excessively low, DTC P0107 will set.

PCM will run diagnostic for this DTC under the following conditions

1. DTC P0121, P0122, or P0123 are not set.
2. Engine is running.
3. Throttle angle is more than zero percent if engine speed is less than 1000 RPM.

DTC will set when MAP sensor signal voltage is less than 0.1 volt (12 kPa) for more than 67 crankshaft revolutions.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Start engine. Using scan tool, check for DTCs. If scan tool indicates DTC P1635 is current, perform diagnosis for DTC P1635. See «DTC P1635: 5-VOLT REFERENCE "A" CIRCUIT»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). If scan tool does not indicate DTC P1635 is current, go to next step.
3. Using scan tool, observe MAP sensor voltage. If scan tool displays less than.1 volt, go to step 5. If scan tool displays.1 volt or more, go to next step.
4. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Select SPECIFIC DTC function then enter this DTC. If scan tool indicates FAILED THIS IGN, go to next step. If scan tool does not indicate FAILED THIS IGN, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
5. Turn ignition off. Disconnect MAP sensor harness connector. (Scheme 10)or (Scheme 15). Turn ignition on. Measure voltage between ground and 5-volt reference circuit (Gray wire) at MAP sensor harness connector terminal "C". If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step 7.
6. Connect a 3-amp fused jumper wire between 5-volt reference circuit (Gray wire) at MAP sensor harness connector terminal "C" and signal circuit (Light Green wire) at MAP sensor harness connector terminal "B". Using scan tool, read MAP sensor voltage. If scan tool displays about 5 volts, go to step 9. If scan tool does not display about 5 volts, go to step 8.
7. Check for open or short to ground in 5-volt reference circuit (Gray wire) between MAP sensor harness connector terminal "C" and PCM harness connector C1 terminal No. 10. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 13. If circuit is okay, go to step 10.
8. Check for open or short to ground in signal circuit (Light Green wire) between MAP sensor harness connector terminal "B" and PCM harness connector C2 terminal No. 25. Repair circuit as necessary, then go to step 13. If circuit is okay, go to step 10.
9. Inspect MAP sensor harness connector for poor connections. Repair connector as necessary, then go to step 13. If connector is okay, go to step 11.
10. Inspect PCM harness connectors for poor connections. Repair connector(s) as necessary, then go to step 13. If connectors are okay, go to step 12.
11. Replace MAP sensor. After repairs, go to step 13.
12. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
13. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
14. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Inspect MAP sensor vacuum source for leaks, restrictions and poor connections. If problem is intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Manifold Absolute Pressure (MAP) sensor responds to changes in intake manifold pressure which gives an indication of engine load. MAP sensor has a 5-volt reference circuit, a low reference circuit, and a signal circuit. PCM supplies 5 volts to MAP sensor on 5-volt reference circuit and provides a ground on low reference circuit. MAP sensor provides a signal to PCM on signal circuit which is relative to pressure changes in the intake manifold. With low manifold absolute pressure such as during idle or deceleration, the PCM should detect a low MAP sensor signal voltage. With high manifold absolute pressure such as ignition on with engine off or wide-open throttle, PCM should detect a high MAP sensor signal voltage. Certain vehicle models will also use MAP sensor in order to calculate Barometric Pressure (BARO) when ignition is turned on with engine off. BARO reading may also be updated whenever engine is operated at wide open throttle. PCM monitors MAP sensor signal for voltage outside of normal range. If PCM detects a MAP sensor signal voltage that is excessively high, DTC P0108 will set.

PCM will run diagnostic for this DTC under the following conditions

1. DTC P0121, P0122 or P0123 are not set.
2. Engine has been running for a length of time that is determined by start-up engine coolant temperature. Length of time ranges from 2 minutes at less than 86°F (30°C) to one second at more than 86°F (30°C).
3. Throttle angle is less than 2 percent if engine speed is less than 3000 RPM.
4. Throttle angle is less than 30 percent if engine speed is more than 3000 RPM.

DTC will set when MAP sensor signal voltage is more than 4.3 volts for more than 67 crankshaft revolutions.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Start engine. Using scan tool, check for DTCs. If scan tool indicates DTC P1635 is current, perform diagnosis for DTC P1635. See «DTC P1635: 5-VOLT REFERENCE "A" CIRCUIT»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). If scan tool does not indicate DTC P1635 is current, go to next step.
3. Correct any engine idle or vacuum problems before proceeding. Let engine idle. Using scan tool, read MAP sensor voltage. If scan tool displays more than 4.3 volts, go to step 5. If scan tool displays 4.3 volts or less, go to next step.
4. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Select SPECIFIC DTC function then enter this DTC. If scan tool indicates FAILED THIS IGN, go to next step. If scan tool does not indicate FAILED THIS IGN, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
5. Turn ignition off. Disconnect MAP sensor harness connector. (Scheme 10)or (Scheme 15). Turn ignition on. Using scan tool, read MAP sensor voltage. If scan tool displays less than.1 volt, go to next step. If scan tool displays.1 volt or more, go to step 8.
6. Disconnect ECT sensor harness connector located near water outlet. Measure voltage between low reference circuit (Black wire on Century; Orange/Black wire on all other models) at MAP sensor harness connector terminal "A" and 5-volt reference circuit (Gray wire) at MAP sensor harness connector terminal "C". If voltage is 4.7-5.2 volts, go to step 11. If voltage is not 4.7-5.2 volts, go to next step.
7. If voltage is more than 5.2 volts, go to step 10. If voltage is not more than 5.2 volts, go to step 9.
8. Check for short to voltage in signal circuit (Light Green wire) between MAP sensor harness connector terminal "B" and PCM harness connector C2 terminal No. 25. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 15. If circuit is okay, go to step 12.
9. Check for open in low reference circuit (Black wire on Century; Orange/Black wire on all other models) between MAP sensor harness connector terminal "A" and PCM harness connector C1 terminal No. 13. Repair circuit as necessary, then go to step 15. If circuit is okay, go to step 12.
10. Check for short to voltage in 5-volt reference circuit (Gray wire) between MAP sensor harness connector terminal "C" and PCM C1 harness connector terminal No. 10. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 15. If circuit is okay, go to step 12.
11. Inspect MAP sensor harness connector for poor connections. Repair connector as necessary, then go to step 15. If connector is okay, go to step 13.
12. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step 15. If connector is okay, go to step 14.
13. Replace MAP sensor. After repairs, go to step 15.
14. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
15. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
16. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Inspect MAP sensor vacuum source for leaks, restrictions and poor connections. If problem is intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Intake Air Temperature (IAT) sensor is a thermistor which measures temperature of air entering engine. PCM applies 5 volts through a pull up resistor. When intake air is cold, sensor resistance is high and PCM will monitor a high signal voltage on IAT sensor signal circuit. As intake air warms, sensor resistance becomes lower causing PCM to monitor a lower voltage. If PCM detects an excessively low IAT sensor signal voltage (high temperature indicated), DTC P0112 will set.

PCM will run diagnostic for this DTC under the following conditions

1. DTC P0101, P0102, P0103, P0117, P0118, P0125, P0128, P0502, P0503, P1114 or P1115 are not set.
2. Engine has been running for more than 10 seconds.
3. Vehicle speed is more than 25 MPH.

DTC will set when IAT signal voltage indicates intake air temperature is more than 275°F (135°C) for 20 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, read IAT parameter. If scan tool displays more than 275°F (135°C), go to step 4. If scan tool does not display more than 275°F (135°C), go to next step.
3. Using scan tool, read and record FAILURE RECORDS data. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays that this DTC FAILED THIS IGN, go to next step. If scan tool does not display that this DTC FAILED THIS IGN, go to «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect IAT sensor harness connector. (Scheme 12), (Scheme 13) or (Scheme 14). Turn ignition on. Using scan tool, read IAT parameter. If scan tool displays less than -34°F (-37°C), go to step 6. If temperature is not less than -34°F (-37°C), go to next step.
5. Turn ignition off. Check for short to ground in signal circuit (Tan wire) between IAT sensor harness connector terminal "B" and PCM harness connector C2 terminal No. 50. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 8. If circuit is okay, go to step 7.
6. Replace IAT sensor. After repairs, go to step 8.
7. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
8. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
9. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Intake Air Temperature (IAT) sensor is a thermistor which measures temperature of the air entering engine. PCM applies 5 volts through a pull-up resistor. When intake air is cold, IAT sensor resistance is high, and PCM will monitor a high signal voltage on IAT sensor signal circuit. As intake air warms, IAT sensor resistance becomes lower, causing PCM to monitor a lower voltage. If PCM detects an excessively high IAT sensor signal voltage, a low temperature is indicated, and DTC P0113 will set.

PCM will run diagnostic for this DTC under the following conditions

1. DTC P0101, P0102, P0103, P0117, P0118, P0125, P0128, P0502, P0503, P1114 or P1115 are not set.
2. Vehicle speed is less than 35 MPH.
3. Mass Airflow (MAF) value is less than 12 grams per second.
4. Engine coolant temperature is more than 140°F (60°C).
5. Engine run time more than 3 minutes.
6. IAT signal voltage indicates an intake air temperature less than -35°F (-37°C).
7. Conditions present for at least 20 seconds.

DTC will set when IAT signal voltage indicates intake air temperature is less than -35°F (-37°C) for 20 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, read IAT sensor parameter. If scan tool displays less than -34°F (-37°C), go to step 4. If scan tool does not display less than -34°F (-37°C), go to next step.
3. Turn ignition on, engine off. Using scan tool, read and record FAILURE RECORDS data. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays that this DTC FAILED THIS IGN, go to next step. If scan tool does not display that this DTC FAILED THIS IGN, go to «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect IAT sensor harness connector. (Scheme 12), (Scheme 13) or (Scheme 14). Connect a 3-amp fused jumper wire between signal circuit (Tan wire) and ground circuit (Black wire) at IAT sensor harness connector. Using scan tool, read IAT sensor parameter. If scan tool displays more than 275°F (135°C), go to step 6. If scan tool does not display more than 275°F (135°C), go to next step.
5. Connect jumper wire between ground and signal circuit (Tan wire) at IAT sensor harness connector terminal "B". Using scan tool, read IAT sensor parameter. If scan tool displays more than 275°F (135°C), go to step 7. If scan tool does not display more than 275°F (135°C), go to step 8.
6. Check for short to voltage in signal circuit (Tan wire) between IAT sensor harness connector terminal "B" and PCM harness connector C2 terminal No. 50. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 13. If circuit is okay, go to step 10.
7. Check for open or high resistance in sensor ground circuit (Black wire) between IAT sensor harness connector terminal "A "and PCM harness connector C1 terminal No. 17. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 13. If circuit is okay, go to step 9.
8. Check for open in signal circuit (Tan wire) between IAT sensor harness connector terminal "B" and PCM harness connector C2 terminal No. 50. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 13. If circuit is okay, go to next step.
9. Check for faulty IAT signal or ground circuit connection at PCM. Repair connector as necessary, then go to step 13. If connections are okay, go to step 12.
10. Check for faulty connections at IAT sensor. Repair connector as necessary, then go to step 13. If connections are okay, go to next step.
11. Replace IAT sensor. After repairs, go to step 13.
12. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
13. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
14. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Engine Coolant Temperature (ECT) sensor is a thermistor which measures temperature of engine coolant. PCM supplies 5 volts to ECT signal circuit. When ECT is cold, ECT sensor resistance is high. When ECT increases, ECT 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 P0117 will set.

PCM will run diagnostic for this DTC when engine is running. DTC will set when ECT sensor circuit indicates an engine coolant temperature of more than 283°F (140°C). Condition must be present for more than 15 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, read ECT sensor parameter. If scan tool displays more than 280°F (138°C), go to step 4 . If scan tool does not display more than 280°F (138°C), go to next step.
3. Turn ignition on, engine off. Using scan tool, read and record FAILURE RECORDS data. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays that this DTC FAILED THIS IGN, go to next step. If scan tool does not display that this DTC FAILED THIS IGN, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) .
4. Turn ignition off. Disconnect ECT sensor harness connector located near water outlet. Turn ignition on. Using scan tool, read ECT sensor parameter. If scan tool displays less than -36°F (-38°C), go to step 6 . If scan tool does not display less than -36°F (-38°C), go to next step.
5. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location) . Check for short to ground or sensor ground in signal circuit (Yellow wire) at ECT sensor harness connector terminal "B". Repair circuit as necessary, then go to step 8 . If circuit is okay, go to step 7 .
6. Replace ECT sensor. After repairs, go to step 8 .
7. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . After repairs, go to next step.
8. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2 . If DTC does not reset, go to next step.
9. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs, system is okay.

An overheating condition may cause this DTC to set. After starting the engine, ECT sensor temperature should rise steadily to about 194°F (90°C), then stabilize when thermostat opens. Test ECT sensor at various temperature levels to check for a skewed sensor. See SENSOR OPERATING RANGE CHARTS - CARS article. A skewed sensor could result in poor driveability concerns. If malfunction is not present at this time, go to DTC P1114: ECT SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE . If an intermittent condition is suspected, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Engine Coolant Temperature (ECT) sensor is a thermistor that measures temperature of engine coolant. PCM supplies 5 volts to ECT signal circuit. When engine coolant is cold, ECT sensor resistance is high. When engine coolant temperature increases, ECT 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 P0118 will set.

PCM will run diagnostic for this DTC when engine is running. DTC will set when ECT sensor circuit indicates an engine coolant temperature of less than -36°F (-38°C). Condition must be present for more than 15 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, observe ECT parameter. If temperature is less than -36°F (-38°C), go to step 4. If temperature is not less than -36°F (-38°C), go to next step.
3. Using scan tool, read and record FAILURE RECORDS data. Turn ignition off and wait 30 seconds. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays that this DTC FAILED THIS IGN, go to next step. If scan tool does not display that this DTC FAILED THIS IGN, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
4. Turn ignition off. Disconnect ECT sensor harness connector located near water outlet. Connect a 3-amp fused jumper wire between ECT sensor harness connector terminals. Turn ignition on. Using scan tool, observe ECT parameter. If temperature is more than 280°F (138°C), go to step 8. If temperature is not more than 280°F (138°C), go to next step.
5. Remove jumper wire. Connect jumper wire between ground and signal circuit (Yellow wire) at ECT sensor harness connector terminal "B". Using scan tool, observe ECT parameter. If temperature is more than 280°F (138°C), go to step 7. If temperature is not more than 280°F (138°C), go to next step.
6. Check for open, high resistance or short to voltage in signal circuit (Yellow wire) between ECT sensor harness connector terminal "B" and PCM harness connector C2 terminal No. 26. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 12. If circuit is okay, go to next step.
7. Check for open in low reference (Black wire on Century; Orange/Black wire on all other models) between ECT sensor harness connector terminal "A" and PCM harness connector C1 terminal No. 13. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 12. If circuit is okay, go to step 9.
8. Inspect ECT sensor harness connector for poor connections. Repair connector as necessary, then go to step 12. If connector is okay, go to step 10.
9. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step 12. If connector is okay, go to step 11.
10. Replace ECT sensor. After repairs, go to step 12.
11. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
12. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
13. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

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 circuits will be necessary in order to diagnose the specific circuit. After starting engine, engine coolant temperature should rise steadily to about 194°F (90°C) then stabilize when thermostat opens. Test ECT sensor at various temperature levels to check for a skewed sensor. See SENSOR OPERATING RANGE CHARTS - CARS article. A skewed sensor could result in poor driveability concerns. If a malfunction is not present at this time, go to DTC P1115: ECT SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE . If an intermittent condition is suspected, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Throttle Position (TP) sensor is used by PCM to determine throttle plate angle for various engine management systems. TP sensor is a potentiometer type sensor with 3 circuits, a 5-volt reference circuit, a low reference circuit, and a signal circuit. PCM provides the TP sensor with a 5-volt reference circuit and a low reference circuit. Rotation of the 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. When conditions for running this DTC are met, PCM will use Manifold Absolute Pressure (MAP) sensor to determine if predicted operating range of TP sensor is correct. If TP sensor is determined to be operating properly and this DTC continues to set, a skewed MAP sensor may cause this DTC to set and should be tested for proper operation.

PCM will run diagnostic for this DTC under the following conditions

1. DTC P0107, P0108, P0122, P0123, P1106, P1107, P1121, or P1122 are not set.
2. Engine has been running longer than 2 minutes.
3. Engine coolant temperature is more than 167°F (75°C).
4. MAP reading is less than 50 kPa for a TP sensor skewed high test, or more than 70 kPa for a TP sensor skewed low test.
5. MAP reading is steady for at least 5 seconds.

DTC P0121 will set when

1. TP sensor reading is more than predicted value when MAP is less than 50 kPa.
2. TP sensor reading is less than predicted value when MAP is more than 70 kPa.
3. Conditions are present for 5 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, monitor TP sensor angle reading while slowly opening throttle. If TP sensor value increases steadily and evenly from closed throttle value to wide open throttle (zero percent to more than 98 percent), go to next step. If TP sensor value does not increase steadily and evenly from closed throttle value to wide open throttle (zero percent to more than 98 percent), go to step 4.
3. Using scan tool, read and record FAILURE RECORDS data. Turn ignition off and wait 30 seconds. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays that this DTC FAILED THIS IGN, go to next step. If scan tool does not display that this DTC FAILED THIS IGN, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
4. Turn ignition off. Disconnect TP sensor harness connector. (Scheme 10), (Scheme 14) or (Scheme 16). Turn ignition on. Using scan tool, observe TP sensor voltage parameter. If scan tool displays zero volts, go to next step. If scan tool does not display zero volts, go to step 6.
5. Turn ignition off. Connect a fused jumper wire between 5-volt reference circuit (Gray wire on Century, Grand Prix, Impala and Monte Carlo; Gray/Black wire on Alero, Grand Am and Malibu) at TP sensor harness connector terminal "A" and signal circuit (Dark Blue wire) at TP sensor harness connector terminal "C". Turn ignition on. Using scan tool, observe TP sensor voltage parameter. If scan tool displays 5 volts, go to step 9. If scan tool does not display 5 volts, go to step 7.
6. Check for short to voltage in signal circuit (Dark Blue wire) between TP sensor harness connector terminal "C" and PCM harness connector C2 terminal No. 66. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 14. If circuit is okay, go to step 12.
7. Check for open or high resistance in 5-volt reference circuit (Gray wire on Century, Grand Prix, Impala and Monte Carlo; Gray/Black wire on Alero, Grand Am and Malibu) between TP sensor harness connector terminal "A" and PCM harness connector C2 terminal No. 33. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 14. If circuit is okay, go to next step.
8. Check for open or high resistance in signal circuit (Dark Blue wire) between TP sensor harness connector terminal "C" and PCM harness connector C2 terminal No. 66. Repair circuit as necessary, then go to step 14. If circuit is okay, go to step 11.
9. Check for open or high resistance in low reference circuit (Black wire) between TP sensor harness connector terminal "B" and PCM harness connector C1 terminal No. 61. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 14. If circuit is okay, go to next step.
10. Inspect TP sensor harness connector for poor connections. Repair connector as necessary, then go to step 14. If connector is okay, go to step 12.
11. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step 14. If connector is okay, go to step 13.
12. Replace TP sensor. After repairs, go to step 14.
13. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
14. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
15. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Scheme 16

Check for a skewed MAP signal. See SENSOR OPERATING RANGE CHARTS - CARS article. A skewed MAP signal may cause PCM to incorrectly determine TP sensor is out of range. Inspect for an unusually low or high MAP reading. If DTC is determined to be intermittent or if TP sensor system is still suspect, go to DTC P1121: TP SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE .

Throttle Position (TP) sensor is used by PCM to determine throttle plate angle for various engine management systems. TP sensor is a potentiometer type sensor with 3 circuits: a 5-volt reference circuit, a low reference circuit and a signal circuit. 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.

PCM will run diagnostic for this DTC when ignition is on. DTC P0122 will set when TP sensor signal voltage is less than .1 volts for more than one second.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, read TP sensor voltage parameter. If scan tool displays less than.1 volt, go to step 4. If scan tool does not display less than.1 volt, go to next step.
3. Using scan tool, read and record FAILURE RECORDS data. Turn ignition off and wait 30 seconds. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays that this DTC FAILED THIS IGN, go to next step. If scan tool does not display that this DTC FAILED THIS IGN, see «DTC P1122: TP SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
4. Turn ignition off. Disconnect TP sensor harness connector. (Scheme 10), (Scheme 14) or (Scheme 16). Connect a fused jumper wire between 5-volt reference circuit (Gray wire on Century, Grand Prix, Impala and Monte Carlo; Gray/Black wire on Alero, Grand Am and Malibu) at TP sensor harness connector terminal "A" and signal circuit (Dark Blue wire) at TP sensor harness connector terminal "C". Turn ignition on. Using scan tool, read TP sensor voltage parameter. If scan tool displays 5 volts, go to step 11. If scan tool does not display 5 volts, go to next step.
5. Disconnect jumper wire. Measure voltage between 5-volt reference circuit (Gray wire on Century, Grand Prix, Impala and Monte Carlo; Gray/Black wire on Alero, Grand Am and Malibu) at TP sensor harness connector terminal "A" and low reference circuit (Black wire) at TP sensor harness connector terminal "B". If voltage is about 5 volts, go to step 9. If voltage is not about 5 volts, go to next step.
6. Check for open or high resistance in 5-volt reference circuit (Gray wire on Century, Grand Prix, Impala and Monte Carlo; Gray/Black wire on Alero, Grand Am and Malibu) between TP sensor harness connector terminal "A" and PCM harness connector C2 terminal No. 33. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 14. If circuit is okay, go to next step.
7. Check for short to ground in all 5-volt reference circuits. See WIRING DIAGRAMS article. Repair circuit(s) as necessary, then go to step 14. If all circuits are okay, go to next step.
8. Measure voltage between 5-volt reference circuit (Gray wire on Century, Grand Prix, Impala and Monte Carlo; Gray/Black wire on Alero, Grand Am and Malibu) at TP sensor harness connector terminal "A" and low reference circuit (Black wire) at TP sensor harness connector terminal "B". While observing voltmeter, individually disconnect each sensor that uses a 5-volt reference. A change in voltage indicates faulty component. Replace faulty component as necessary, then go to step 14. If voltage does not change, go to step 10.
9. Check for open, high resistance or short to ground in signal circuit (Dark Blue wire) between TP sensor harness connector terminal "C" and PCM harness connector C2 terminal No. 66. Repair circuit as necessary, then go to step 14. If circuit is okay, go to next step.
10. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step 14. If connector is okay, go to step 13.
11. Inspect TP sensor harness connector for poor connections. Repair connector as necessary, then go to step 14. If connector is okay, go to next step.
12. Replace TP sensor. After repairs, go to step 14.
13. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
14. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
15. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Throttle Position (TP) sensor is used by PCM to determine throttle plate angle for various engine management systems. TP sensor is a potentiometer type sensor with 3 circuits: a 5-volt reference circuit, a low reference circuit, and a signal circuit. 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 position provides PCM with a signal voltage from less than one volt to more than 4 volts through TP sensor signal circuit.

PCM will run diagnostic for this DTC when ignition is on. DTC P0123 will set when TP sensor signal voltage is more than 4.9 volts for longer than one second.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, read TP sensor voltage parameter with throttle closed. If scan tool displays more than 4.9 volts, go to step 4. If scan tool does not display more than 4.9 volts, go to next step.
3. Using scan tool, read and record FAILURE RECORDS data. Turn ignition off and wait 30 seconds. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays that this DTC FAILED THIS IGN, go to next step. If scan tool does not display that this DTC FAILED THIS IGN, see «DTC P1121: TP SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
4. Turn ignition off. Disconnect TP sensor harness connector. (Scheme 10), (Scheme 14) or (Scheme 16). Turn ignition on. Using scan tool, read TP sensor voltage parameter. If scan tool displays zero volts, go to next step. If scan tool does not display zero volts, go to step 8.
5. Measure voltage between ground and 5-volt reference circuit (Gray wire on Century, Grand Prix, Impala and Monte Carlo; Gray/Black wire on Alero, Grand Am and Malibu) at TP sensor harness connector terminal "A". If voltage is 5 volts, go to next step. If voltage is not 5 volts, go to step 9.
6. Connect a test light between battery positive and low reference circuit (Black wire) at TP sensor harness connector terminal "B". If test light illuminates, go to step 10. If test light does not illuminate, go to next step.
7. Check for open or high resistance in low reference circuit (Black wire) between TP sensor harness connector terminal "B" and PCM harness connector C1 terminal No. 61. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 18. If circuit is okay, go to step 15.
8. Check for short to voltage in signal circuit (Dark Blue wire) between TP sensor harness connector terminal "C" and PCM harness connector C2 terminal No. 66. Repair circuit as necessary, then go to step 18. If circuit is okay, go to step 15.
9. Check for short to voltage in all 5-volt reference circuits. See WIRING DIAGRAMS article. Repair as necessary, then go to step 18. If all circuits are okay, go to next step.
10. Measure voltage between 5-volt reference circuit (Gray wire on Century, Grand Prix, Impala and Monte Carlo; Gray/Black wire on Alero, Grand Am and Malibu) at TP sensor harness connector terminal "A" and low reference circuit (Black wire) at TP sensor harness connector terminal "B". Observe voltage while commanding EGR to 100 percent with scan tool. If voltage changes while commanding EGR, go to next step. If voltage does not change while commanding EGR, go to step 14.
11. Leave voltmeter connected. Disconnect EGR valve harness connector. Observe voltage while commanding EGR to 100 percent with scan tool. If voltage changes while commanding EGR, go to step 13. If voltage does not change while commanding EGR, go to next step.
12. Replace EGR valve. After repairs, go to step 18.
13. Repair short between EGR solenoid control circuit and 5-volt reference circuit. See WIRING DIAGRAMS article. After repairs, go to step 18.
14. Inspect TP sensor harness connector for poor connections. Repair connector as necessary, then go to step 18. If connector is okay, go to step 16.
15. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step 18. If connector is okay, go to step 17.
16. Replace TP sensor. After repairs, go to step 18.
17. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
18. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
19. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Engine Coolant Temperature (ECT) sensor monitors temperature of engine coolant. This input is used by PCM for engine control and as an enabling criteria for some diagnostics. Air flow 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 set when there has been excessive time to reach a minimum coolant temperature required for closed loop fuel control. This diagnostic is broken into 3 temperature regions.

PCM will run diagnostic for this DTC under the following conditions

1. This diagnostic will only run once per ignition cycle within enabling conditions.
2. DTCs P0112, P0113, P0117, P0118, P1111, P1112, P1114 or P1115 are not set.
3. Minimum air temperature is more than 19°F (-7°C).
4. Start up engine coolant temperature is less than 104°F (40°C).
5. In region 1, air temperature is more than 50°F (10°C) and start-up coolant temperature is more than 14°F (-10°C).
6. In region 2, air temperature is more than 19°F (-7°C) and start-up coolant temperature is 19-50°F (-7 to 10°C).
7. In region 3, air temperature is more than 19°F (-7°C) and start-up coolant temperature is 19-50°F (-7 to 10°C).

In region 1, DTC will set when the following conditions exist

1. Engine run time is more than 6 seconds to achieve closed loop temperature of 14°F (-10°C).
2. Calibrated minimum amount of air flow has been exceeded.
3. Maximum idle time has been less than 5 seconds.

In region 2, DTC will set when the following conditions exist

1. Engine run time is more than 154 seconds to achieve closed loop temperature of 14°F (-10°C).
2. Calibrated minimum amount of air flow has been exceeded.
3. Maximum idle time has been less than 120 seconds.

In region 3, DTC will set when the following conditions exist

1. Engine run time is more than 287 seconds to achieve closed loop temperature of 14°F (-10°C).
2. Calibrated minimum amount of air flow has been exceeded.
3. Maximum idle time has been less than 225 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Check coolant level. If coolant level is okay, go to next step. If coolant level is low, repair cooling system problem as necessary.
3. Turn ignition off. Disconnect ECT sensor harness connector located near water outlet. Connect a 3-amp fused jumper wire between ECT sensor harness connector terminals. Turn ignition on. Using scan tool, read engine coolant temperature. If scan tool displays more than 280°F (138°C), go to step 7. If scan tool does not display more than 280°F (138°C), go to next step.
4. Turn ignition off. Disconnect jumper wire. Connect jumper wire between ground and signal circuit (Yellow wire) at ECT sensor harness connector terminal "B". Turn ignition on. Using scan tool, read engine coolant temperature. If scan tool displays more than 280°F (138°C), go to next step. If scan tool does not display more than 280°F (138°C), go to step 6.
5. Repair open or high resistance in low reference circuit (Black wire on Century; Orange/Black wire on all other models) between ECT sensor harness connector terminal "A" and PCM harness connector C1 terminal No. 13. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). After repairs, go to step 10.
6. Repair open or high resistance in signal circuit (Yellow wire) between ECT sensor harness connector terminal "B" and PCM harness connector C2 terminal No. 26. After repairs, go to step 10.
7. Remove ECT sensor. Place ECT sensor and a thermometer in heated water. Measure resistance between ECT sensor terminals, with water at specified temperatures. See «ECT SENSOR RESISTANCE»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table. If resistance values are close to specifications, go to next step. If resistance values are not close to specifications, go to step 9.
8. Install ECT sensor. After installing sensor, check thermostat for proper operation. Replace thermostat as necessary. Test is complete.
9. Replace ECT sensor. After repairs, go to next step.
10. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
11. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

ECT SENSOR RESISTANCE

DTC P0125 is designed to detect a skewed ECT sensor.

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

Diagnostic will only run once per ignition cycle under the following enabling conditions

1. DTCs P0112, P0113, P0117, P0118, P1111, P1112, P1114, or P1115 are not set.
2. Engine coolant temperature is more than -40 to 172°F (-40 to -7°C).
3. Air temperature is more than 19°F (-7°C).
4. Engine has been running for more than 2 minutes and less than 30 minutes.
5. Vehicle speed has been more than 15 mph for more than one mile.
6. Mass airflow average reading is more than 15 grams per second.

DTC P0128 will set when length of time for engine coolant to reach a preset temperature has been exceeded.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Check coolant level. If coolant is low, repair cooling system problem. If coolant level is okay, go to next step.
3. Turn ignition off. Disconnect ECT sensor harness connector located near water outlet. Connect a 3-amp fused jumper wire between ECT sensor harness connector terminals. Turn ignition on. Using scan tool, observe ECT sensor temperature. If scan tool displays more than 280°F (138°C), go to step 7. If scan tool does not display more than 280°F (138°C), go to next step.
4. Turn ignition off. Disconnect jumper wire. Connect jumper wire between ground and signal circuit (Yellow wire) at ECT sensor harness connector terminal "B". Turn ignition on. Using scan tool, observe ECT sensor temperature. If scan tool displays more than 280°F (138°C), go to next step. If scan tool does not display more than 280°F (138°C), go to step 6.
5. Repair open or high resistance in low reference circuit (Black wire on Century; Orange/Black wire on all other models) between ECT sensor harness connector terminal "A" and PCM harness connector C1 terminal No. 13. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). After repairs, go to step 10.
6. Repair open or high resistance in signal circuit (Yellow wire) between ECT sensor harness connector terminal "B" and PCM harness connector C2 terminal No. 26. After repairs, go to step 10.
7. Remove ECT sensor. Place ECT sensor and a thermometer in heated water. Measure resistance between ECT sensor terminals, with water at specified temperatures. See «ECT SENSOR RESISTANCE»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table under DTC P0125: ECT EXCESSIVE TIME TO ENTER CLOSED LOOP FUEL CONTROL. If resistance values are close to specifications, go to next step. If resistance values are not close to specifications, go to step 9.
8. Reinstall ECT sensor. Repair cooling system problem causing engine to not reach normal operating temperature.
9. Replace ECT sensor. After repairs, go to next step.
10. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
11. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

PCM supplies a bias voltage of about 450 mV between the HO2S signal circuit and the HO2S low reference circuit. When measured with a 10-megohm DVOM, this may display as low as 350 mV. HO2S signal varies from about 800 mV when exhaust is rich, to about 50 mV when exhaust is lean. If HO2S 1 voltage remains at or near the 450 millivolt bias for an extended period of time, DTC P0134 is set. If signal amplitude of HO2S 1 sensor exceeds the no activity (P0134) thresholds but will not allow closed loop operation, DTC P0130 will set.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201-P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
2. Engine has been running for at least 4 minutes.
3. Engine coolant temperature is at least 158°F (70°C).
4. Engine RPM is 550-3000 RPM.
5. Mass airflow is 8-35 grams per second.
6. Throttle angle is 3-35 percent.
7. Ignition voltage is 9-18 volts.

DTC will set when PCM detects an active HO2S with an improper voltage amplitude.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, clear DTCs and reset fuel trim values. Start engine and let it idle until normal operating temperature is reached. Using scan tool, read HO2S 1 voltage parameter. If scan tool displays 300-600 mV, go to step 4. If scan tool does not display 300-600 mV, go to next step.
3. Condition that set this DTC is not present. This DTC may have been set by one of the following conditions: water intrusion into HO2S 1 harness connector, intermittently open HO2S 1 high signal circuit, intermittently open HO2S low reference circuit, high resistance in HO2S low reference circuit, high resistance in PCM ground circuits, inoperative HO2S heater, poor HO2S or PCM connector terminal contact, exhaust system leak (typically within 12" upstream of HO2S) or defective HO2S. If a problem is found, repair as necessary, then go to step 17. If no problem is found, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect HO2S 1 harness connector. (Scheme 10)or (Scheme 11). Connect a jumper wire between ground and low reference circuit at HO2S 1 harness connector terminal "A". See «HO2S 1 CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table. Connect another jumper wire between ground and signal circuit (Purple wire) at HO2S 1 harness connector terminal "B". Turn ignition on. Using scan tool, read HO2S 1 voltage parameter. If scan tool displays less than 20 mV, go to step 7. If scan tool does not display less than 20 mV, go to next step.
5. Turn ignition off. Remove jumper wires. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Measure resistance of signal circuit (Purple wire) between HO2S 1 harness connector terminal "B" and PCM harness connector C2 terminal No. 10. (Scheme 5)or (Scheme 6). Also, measure resistance of low reference circuit between HO2S harness connector terminal "A" and PCM harness connector C1 terminal No. 12. If resistance is less than 5 ohms on both circuits, go to next step. If resistance is not less than 5 ohms, go to step 9.
6. Check for proper PCM connector terminal contact. Repair connector as necessary, then go to step 17. If connector is okay, go to step 16.
7. Turn ignition off. Remove jumper wires. Connect a test light between ignition 1 voltage circuit at HO2S 1 harness connector terminal "D" and heater control circuit (Black/White wire) at HO2S 1 harness connector terminal "C". Start engine. If test light illuminates, go to next step. If test light does not illuminate, go to step 10.
8. Turn ignition off. Reconnect HO2S harness connector. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Measure resistance between HO2S 1 low reference circuit at PCM harness connector C1 terminal No. 12 and one of the PCM ground circuit terminals. See WIRING DIAGRAMS article. (Scheme 5)or (Scheme 6). If resistance is less than 500 ohms, go to step 12. If resistance is not less than 500 ohms, go to step 11.
9. Repair circuit with high resistance. After repairs, go to step 17.
10. Repair ignition 1 voltage circuit or heater low control circuit. Probable causes include the following: open circuit, high circuit resistance, poor ground connection or open heater fuse (other DTCs should set). After repairs, go to step 17.
11. Repair high resistance between HO2S low reference circuit and PCM ground circuit. Probable causes include the following: poor HO2S connector terminal contact, open or high resistance in low reference circuit at sensor pigtail (requires HO2S replacement), poor PCM ground connection, high PCM ground circuit resistance or ungrounded exhaust system. After repairs, go to step 17.
12. Check for exhaust system leaks upstream of HO2S 1. The leak may be very small and will typically be within 12" of HO2S. Repair exhaust system as necessary. After repairs, go to step 17. If exhaust system is okay, go to next step.
13. Allow engine to cool to ambient temperature. Again, measure resistance between HO2S 1 low reference circuit at PCM harness connector C1 terminal No. 12 and one of the PCM ground circuit terminals. If resistance is less than 500 ohms, go to step 15. If resistance is not less than 500 ohms, go to next step.
14. Remove HO2S 1. Clean HO2S mounting threads. Apply anti-seize compound (5613695 or equivalent) to sensor threads. Install HO2S, and tighten to 31 ft. lbs. (42 N.m). Again, measure resistance between HO2S 1 low reference circuit at PCM harness connector C1 terminal No. 12 and one of the PCM ground circuit terminals. If resistance is less than 500 ohms, go to step 17. If resistance is not less than 500 ohms, go to next step.
15. Replace HO2S 1. After repairs, go to step 17.
16. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
17. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
18. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

HO2S 1 CIRCUIT IDENTIFICATION

PCM supplies a bias voltage of about 450 mV between HO2S signal and low circuits. When measured with a 10-megohm DVOM, this may display as low as 350 mV. HO2S varies voltage from about 1000 mV when exhaust is rich, to about 100 mV when exhaust is lean. PCM constantly monitors HO2S signal during closed loop operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary. If HO2S 1 voltage remains excessively low for an extended time, DTC P0131 will set.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201-P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
2. System voltage is more than 9 volts.
3. Closed loop commanded air/fuel ratio is 12:1-16.5:1.
4. Throttle angle is 3-35 percent.

DTC will set when HO2S 1 signal voltage remains less than 175 mV during normal closed loop operation, or HO2S 1 signal voltage remains less than 600 mV during power enrichment mode fuel control operation. Either condition must be present for 50 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Start engine and warm to normal operating temperature. Using scan tool, observe HO2S 1 voltage. If scan tool displays less than 175 mV, go to step 4. If scan tool does not display less than 175 mV, go to next step.
3. Condition that set this DTC is not present. This DTC may have been set by one of the following conditions: HO2S signal wire intermittently shorted to engine ground or to HO2S low reference circuit. HO2S connector water intrusion. Exhaust leak between HO2S and engine. Intermittent lean condition resulting from vacuum leaks, an incorrect or defective PCV valve or system, incorrect fuel pressure, lean fuel injectors, or an inaccurate MAF sensor. A lean engine condition during Power Enrichment operation. If a problem is found, repair as necessary. After repairs, go to step 10. If no problem is found, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect HO2S 1 harness connector. (Scheme 10)or (Scheme 11). Connect a jumper wire between ground and low reference circuit at HO2S harness connector terminal "A". See «HO2S 1 CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table under DTC P0130: HO2S 1 - INSUFFICIENT ACTIVITY FOR CLOSED LOOP OPERATION. Turn ignition on. Using scan tool, read the HO2S 1 voltage parameter. If scan tool displays 351-551 mV, go to next step. If scan tool does not display 351-551 mV, 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, an incorrect or defective PCV valve or system, incorrect fuel pressure, lean fuel injectors, or an inaccurate MAF sensor. If a problem is found, repair as necessary. After repairs, go to step 10. If no problem is found, go to step 8.
6. Turn ignition off. Remove jumper wire. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Measure and record resistance between ground and HO2S 1 signal circuit (Purple wire) at PCM harness connector C2 terminal No. 10. (Scheme 5)or (Scheme 6). Also, measure and record resistance between HO2S 1 signal circuit (Purple wire) at PCM harness connector C2 terminal No. 10 and HO2S 1 low reference circuit at PCM harness connector C1 terminal No. 12. If resistance is infinite on both checks, go to step 9. If resistance is not infinite on both checks, go to next step.
7. Repair short to ground or short to low reference circuit in HO2S 1 signal circuit. After repairs, go to step 10.
8. Replace HO2S 1. After repairs, go to step 10.
9. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
10. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
11. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

PCM supplies a bias voltage of about 450 mV between HO2S signal circuit and HO2S low reference circuit. When measured with a 10 megohm DVOM, voltage may read as low as 350 mV. HO2S signal varies from about 800 mV when exhaust is rich to about 50 mV when exhaust is lean. PCM constantly monitors HO2S signal during closed loop operation and compensates for a rich or a lean condition by decreasing or increasing the injector pulse width as necessary. If HO2S 1 signal voltage remains excessively high for an extended period of time, DTC P0132 will set.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201-P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
2. System voltage is more than 9 volts.
3. Closed loop commanded air/fuel ratio is 12:1-16.5:1.
4. Throttle angle is 3-35 percent.

DTC will set when HO2S 1 signal voltage remains more than 975 mV during normal closed loop operation, or HO2S 1 signal voltage remains more than 200 mV during deceleration fuel mode operation. Either of these conditions must be present for 50 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Allow engine to idle until normal operating temperature is reached. Using scan tool, read HO2S 1 voltage. If scan tool displays less than 975 mV, go to next step. If scan tool does not display less than 975 mV, 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: A HO2S signal wire intermittently shorted to engine ground or to HO2S low reference circuit. HO2S connector water intrusion. Silicone contamination of HO2S. An intermittently rich engine condition caused by one of the following conditions: EVAP canister purge system malfunction, fuel contamination of engine oil, incorrect fuel pressure, leaking fuel pressure regulator, rich fuel injectors, inaccurate MAF sensor. A rich engine condition during deceleration fuel mode operation. Repair any of the above or similar engine conditions as necessary. After repairs, go to step 10. If no problems are found, go to «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
4. Turn ignition off. Disconnect HO2S 1 harness connector. (Scheme 11)or (Scheme 10). Connect a jumper wire between ground and low reference circuit at HO2S harness connector terminal "A". See «HO2S 1 CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table under DTC P0130: HO2S 1 - INSUFFICIENT ACTIVITY FOR CLOSED LOOP OPERATION. Turn ignition on. Using scan tool, read HO2S 1 voltage parameter. If scan tool displays 351-551 mV, go to next step. If scan tool does not display 351-551 mV, go to step 6.
5. HO2S is detecting a rich exhaust condition or may be contaminated. Check for one of the following conditions: water intrusion in HO2S connector, silicone contamination of HO2S, fuel contamination in engine oil, EVAP canister purge system malfunction, incorrect fuel pressure, rich fuel injectors or inaccurate MAF sensor. Repair any of the above or similar engine conditions as necessary. After repairs, go to step 10. If no problems are found, go to step 8.
6. Turn ignition off. Remove jumper wire. Disconnect PCM harness connector C2. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Turn ignition on. Measure voltage between ground and HO2S 1 signal circuit (Purple wire) at PCM harness connector C2 terminal No. 10. (Scheme 5)or (Scheme 6). If voltage is more than 20 mV, go to next step. If voltage is not more than 20 mV, go to step 9.
7. Repair short to voltage in HO2S 1 signal circuit. After repairs, go to step 10.
8. Replace HO2S 1. After repairs, go to step 10.
9. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
10. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
11. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Check the following items

1. Fuel pressure. See appropriate BASIC DIAGNOSTIC PROCEDURES article. System will go rich if pressure is too high. PCM can compensate for some increase. However, if fuel pressure is too high, DTC P0132 may be set.
2. Fuel injectors Perform injector balance test. See appropriate SYSTEM & COMPONENT TESTING article.
3. Inspect EVAP canister for fuel saturation. If canister is full of fuel, inspect canister and hoses.
4. Disconnect MAF sensor and see if rich condition is corrected. If so, replace MAF sensor.
5. Test for a leaking fuel pressure regulator diaphragm by checking vacuum line to regulator for presence of fuel.
6. An intermittent TP sensor output will cause system to go rich due to a false indication of engine accelerating.
7. A HO2S. If HO2S is internally shorted, HO2S voltage displayed on scan tool will be more than one volt. Disconnect affected HO2S and jumper HO2S low reference circuit to ground with ignition on. If displayed HO2S voltage changes from more than 1000 mV to about 450 mV, replace HO2S.
8. Silicone contamination of HO2S can also cause a high HO2S voltage to be indicated. This condition is indicated by a powdery white deposit on portion of HO2S that is exposed to exhaust stream. If you notice contamination, replace affected HO2S.
9. An open HO2S high signal or low reference circuit or inoperative HO2S. A poor connection or an open in HO2S high signal or low reference circuit can cause this DTC to set during deceleration fuel mode.
10. An HO2S which is inoperative and not allowing a full voltage swing between rich and lean thresholds can also cause this condition. Operate vehicle while monitoring HO2S voltage with a scan tool. If HO2S voltage is limited within a range of 300-600 mV, check HO2S high signal and low reference circuit wiring and associated terminal connections. If wiring and connections are okay, replace HO2S.
11. If problem is intermittent, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.

PCM continuously monitors HO2S activity for 100 seconds. During this monitoring period, PCM counts the number of times that a rich to lean and lean to rich response is indicated and adds the amount of time it took in order to complete all transitions. With this information, an average time for each transition can be determined. If average response time is too slow, a DTC P0133 will be set. A lean to rich transition is indicated when HO2S voltage changes from less than 300 mV to more than 600 mV. A rich to lean transition is indicated when HO2S voltage changes from more than 600 mV to less than 300 mV. An HO2S that responds too slowly is likely to be inoperative and should be replaced.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201- P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
2. Transmission is not in Park or Neutral.
3. Engine has been running for at least 4 minutes.
4. Mass airflow is 8-35 grams per second.
5. Engine speed is 550-3000 RPM.
6. Throttle angle is 3-35 percent.
7. System voltage is 9-18 volts.
8. Engine coolant temperature is more than 158°F (70°C).

DTC will set when HO2S 1 lean to rich average transition response time was more than 95 milliseconds, or HO2S 1 rich to lean average transition response time was more than 105 milliseconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. If any other DTCs (except DTC P1134) are set, diagnose those DTCs first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . Start engine and warm to normal operating temperature. Operate vehicle within conditions required to set DTC. Using scan tool, read SPECIFIC DTC. If scan tool indicates that this DTC FAILED THIS IGN, go to next step. If scan tool does not indicate that this DTC FAILED THIS IGN, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
3. If scan tool also displays DTC P1134 FAILED THIS IGN, go to step 6 . If scan tool does not display this DTC, go to next step.
4. Visually or physically inspect for the following items: improperly installed and secure HO2S 1, corrosion on terminals, damaged wiring or poor connections at sensor or PCM. If a problem is found, repair as necessary, then go to step 7 . If no problem is found, go to next step.
5. Check for exhaust leaks. Repair exhaust system as necessary. After repairs, go to step 7 . If exhaust system is okay, go to next step.
6. Replace HO2S 1. After repair, go to next step.
7. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2 . If DTC does not reset, go to next step.
8. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs, system is okay.

PCM supplies a bias voltage of about 450 mV between the HO2S high signal circuit and low reference circuit. When measured with a 10-megohm DVOM, this voltage may display as low as 350 mV. HO2S signal varies from about 800 mV when exhaust is rich, to about 50 mV when exhaust is lean. If HO2S 1 voltage remains at or near the 450 mV bias for an extended period of time, DTC P0134 is set.

PCM will run diagnostic for this DTC under the following conditions

1. DTC P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201- P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
2. Engine has been running for at least 4 minutes.
3. Ignition voltage is 90-18 volts.

DTC will set when HO2S 1 signal voltage remains between 408-512 mV for more than 30 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, clear DTCs. Reset fuel trim values. Start and idle engine until normal operating temperature is reached. Using scan tool, observe HO2S 1 voltage parameter. If voltage is fixed within 408-512 mV, go to step 4. If voltage is not fixed within 408-512 mV, go to next step.
3. Condition that set this DTC is not present. This DTC may have been set by one of the following conditions: HO2S connector water intrusion. An intermittently open HO2S high signal or low reference circuit. An HO2S low reference circuit with high resistance to ground. High resistance in PCM ground circuits. An inoperative HO2S heater. Poor HO2S or PCM connector terminal contact. An exhaust system leak (typically within 12" upstream of HO2S). A defective HO2S. If a problem is found, repair as necessary, then go to step 17. If no problems were found, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect HO2S 1 harness connector. (Scheme 11)or (Scheme 10). Connect a jumper wire between ground and low reference circuit at HO2S harness connector terminal "A". See «HO2S 1 CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table under DTC P0130: HO2S 1 - INSUFFICIENT ACTIVITY FOR CLOSED LOOP OPERATION. Connect another jumper wire between ground and signal circuit (Purple wire) at HO2S 1 harness connector terminal "B". Turn ignition on. Using scan tool, read HO2S 1 voltage parameter. If scan tool displays less than 20 mV, go to step 7. If scan tool does not display less than 20 mV, go to next step.
5. Turn ignition off. Remove jumper wires. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Check continuity of the following circuits: HO2S signal circuit (Purple wire) between HO2S 1 harness connector terminal "B" and PCM harness connector C2 terminal No. 10. HO2S low reference circuit between PCM harness connector C1 terminal No. 29 PCM harness connector C2 terminal No. 80. HO2S low reference circuit between HO2S harness connector terminal "A" and PCM harness connector C1 terminal No. 12. (Scheme 5)or (Scheme 6). See «HO2S 1 CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table under DTC P0130: HO2S 1 - INSUFFICIENT ACTIVITY FOR CLOSED LOOP OPERATION. If resistance of all measured circuits is less than 5 ohms, go to next step. If resistance of all measured circuits is not less than 5 ohms, go to step 9.
6. Check for proper PCM connector terminal contact. Repair PCM terminals as necessary, then go to step 17. If connectors are okay, go to step 16.
7. Remove jumper wires. Connect a test light between ignition 1 voltage circuit at HO2S 1 harness connector terminal "D" and heater control circuit (Black/White wire) at HO2S 1 harness connector terminal "C". Start engine. If test light illuminates, go to next step. If test light does not illuminate, go to step 10.
8. Turn ignition off. Reconnect HO2S 1 harness connector. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Measure resistance between HO2S low reference circuit at PCM harness connector C1 terminal No. 12 and one of the PCM ground circuit terminals. (Scheme 5)or (Scheme 6). See WIRING DIAGRAMS article. If resistance is less than 500 ohms, go to step 12. If resistance is not less than 500 ohms, go to step 11.
9. Repair circuit with high resistance. After repair, go to step 17.
10. Repair ignition 1 voltage or heater low control circuit. Probable causes include the following: open circuit, high circuit resistance, poor ground connection or open heater fuse (other DTCs should set). After repairs, go to step 17.
11. Repair high resistance between HO2S low reference circuit and PCM ground circuit. Probable causes include the following: Poor HO2S connector terminal contact. Open or high resistance in sensor harness low reference circuit (requires HO2S replacement). Poor PCM ground connection. High PCM ground circuit resistance. Ungrounded exhaust system. After repairs, go to step 17.
12. Check for exhaust system leaks upstream of HO2S. Leak may be very small and will typically be within 12" of HO2S. Repair exhaust system as necessary, then go to step 17. If exhaust system is okay, go to next step.
13. Allow engine to cool to ambient temperature. Again, measure resistance between HO2S low reference circuit at PCM harness connector C1 terminal No. 12 and one of the PCM ground circuit terminals. If resistance is less than 500 ohms, go to step 15. If resistance is not less than 500 ohms, go to next step.
14. Remove HO2S 1. Clean HO2S mounting threads. Apply Anti-Seize Compound (5613695 or equivalent) to sensor threads. Tighten HO2S to 31 ft. lbs. (42 N.m). Again, measure resistance between HO2S low reference circuit at PCM harness connector C1 terminal No. 12 and one of the PCM ground circuit terminals. If resistance is less than 500 ohms, go to step 17. If resistance is not less than 500 ohms, go to next step.
15. Replace HO2S1. After repair, go to step 17.
16. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
17. Using scan tool, read and record FAILURE RECORDS data, and clear DTCs. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, select SPECIFIC DTC INFO for this DTC. If scan tool indicates that this DTC FAILED THIS IGN, go to step 2. If scan tool does not indicate that this DTC FAILED THIS IGN, go to next step.
18. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Heated Oxygen Sensors (HO2S) are used to minimize amount of time required to enter closed loop fuel control operation and to allow accurate catalyst monitoring. HO2S 1 heater is fed power directly from ignition 1. HO2S 1 heater control circuit or heater ground is connected to PCM. PCM controls HO2S heater operation by grounding control circuit via an internal solid state device called a driver. The driver for HO2S 1 heater control circuit has the ability to measure amount of current drawn by the controlled device.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201- P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
2. System voltage more than 9 volts and less than 18 volts.
3. Engine run time more than 4 minutes.
4. Engine coolant temperature more than 158°F (70°C).
5. Engine speed is 650-2500 RPM.
6. Airflow is 4-26 grams per second.

DTC will set when HO2S 1 heater current is not within calibrated range.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Start engine and allow idle to stabilize for about one minute. Engine should be at normal operating temperature. Using scan tool, monitor O2 heater current parameter. If scan tool displays 0.25-0.85 amp, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM. If scan tool does not display 0.25-0.85 amp, go to next step.
3. On Century, check OXY SEN fuse No. 29 (15-amp). On Grand Prix, check IGN-UH fuse (15-amp). On Malibu, check ERLS fuse No. 47 (10-amp). On all models, fuses are located in underhood fuse block. If fuse is blown, go to step 13. If fuse is okay, go to next step.
4. Turn ignition on. Disconnect HO2S 1 harness connector. (Scheme 10)or (Scheme 11). Connect test light between ground and ignition 1 voltage circuit at HO2S 1 harness connector terminal "D". See «HO2S 1 CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table under DTC P0130: HO2S 1 - INSUFFICIENT ACTIVITY FOR CLOSED LOOP OPERATION. If test light illuminates, go to next step. If test light does not illuminate, go to step 8.
5. Connect test light between ignition 1 voltage circuit at HO2S 1 harness connector terminal "D" and heater low control circuit (Black/White wire) at HO2S 1 harness connector terminal "C". Start engine. If test light illuminates, go to next step. If test light does not illuminate, go to step 7.
6. Turn ignition off and on. If test light illuminates, go to step 10. If test light does not illuminate, go to step 11.
7. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Measure resistance of heater low control circuit (Black/White wire) between HO2S 1 harness connector terminal "C" and PCM harness connector C2 terminal No. 37. (Scheme 5)or (Scheme 6). If resistance is 0-5 ohms, go to step 14. If resistance is not 0-5 ohms, go to step 9.
8. Repair open in ignition 1 voltage circuit. See WIRING DIAGRAMS article. After repairs, go to step 16.
9. Repair open or high resistance in HO2S 1 heater low control circuit. After repairs, go to step 16.
10. Repair short to ground in HO2S 1 heater low control circuit. After repairs, go to step 16.
11. Check for poor connections at HO2S 1 harness connector. Repair connector as necessary, then go to step 16. If connector is okay, go to next step.
12. Replace HO2S 1. After repairs, go to step 16.
13. Repair short to ground in ignition 1 voltage circuit and replace fuse. See WIRING DIAGRAMS article. After repairs, go to step 16.
14. Check for poor connections at PCM harness connectors. Repair connectors as necessary, then go to step 16. If connectors are okay, go to next step.
15. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
16. Start engine and allow idle to stabilize for about one minute. Engine should be at normal operating temperature. Using scan tool, monitor O2 heater current parameter. If scan tool displays 0.25-0.85 amp, go to next step. If scan tool does not display 0.25-0.85 amp, go to step 2.
17. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

To control emissions of Hydrocarbons (HC), Carbon Monoxide (CO), and Oxides of Nitrogen (NOx), a 3-way catalytic converter is used. Catalyst within converter promotes a chemical reaction which oxidizes HC and CO present in exhaust gas, converting them into harmless water vapor and carbon dioxide. Catalyst also reduces NOx, converting it to nitrogen. PCM has the ability to monitor this process using HO2S 1 and HO2S 2 heated oxygen sensors. HO2S 1 sensor produces an output signal which indicates amount of oxygen present in exhaust gas entering 3-way catalytic converter. HO2S 2 sensor produces an output signal which indicates oxygen storage capacity of catalyst; this in turn indicates the catalyst's ability to convert exhaust gases efficiently. If catalyst is operating efficiently, HO2S 1 signal will be far more active than that produced by HO2S 2 sensor. If HO2S 2 signal voltage remains excessively low for an extended period of time, DTC P0137 will set.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201- P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
2. Closed loop commanded air/fuel ratio is 12:1-16.5:1.
3. Throttle angle is 3-40 percent.

DTC will set when HO2S 2 signal voltage remains less than 30 mV during normal closed loop operation, or HO2S 2 signal voltage remains less than 550 mV during power enrichment mode fuel control operation. Either condition must be present for up to 2.5 minutes.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Start engine and allow it to reach operating temperature. Operate vehicle under conditions required to set DTC. Using scan tool, read HO2S 2 voltage. If voltage remains less than 30 mV, go to step 4. If voltage does not remain less than 30 mV, go to next step.
3. Turn engine off. Turn ignition on. Using scan tool, read and record FAILURE RECORDS data. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool indicates that this DTC FAILED THIS IGN, go to next step. If scan tool does not indicate that this DTC FAILED THIS IGN, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
4. Disconnect HO2S 2 harness connector. (Scheme 17)or (Scheme 18). Connect a jumper wire between ground and low reference circuit (Tan/White wire) at HO2S 2 harness connector terminal "A". Using scan tool, read HO2S 2 voltage. If voltage is about 450 mV, go to step 8. If voltage is not about 450 mV, go to next step.
5. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Check for short to ground or short to HO2S low circuit in signal circuit (Purple/White wire) between HO2S 2 harness connector terminal "B" and PCM harness connector C2 terminal No. 11. (Scheme 5)or (Scheme 6). If circuit is shorted, go to next step. If circuit is okay, go to step 7.
6. Repair circuit as necessary. After repairs, go to step 9.
7. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to step 9.
8. Replace HO2S 2. After repairs, go to next step.
9. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
10. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Scheme 17

Scheme 18

Inspect for the following conditions

1. Heated oxygen sensor wiring. Sensor pigtail may be contacting exhaust system.
2. Poor PCM-to-engine grounds.
3. Fuel pressure. System will go lean if pressure is too low. PCM can compensate for some decrease. However, if fuel pressure is too low, DTC P0137 will set.
4. Lean injectors. See appropriate SYSTEM & COMPONENT TESTING article.
5. Disconnected or damaged vacuum hoses. See appropriate VACUUM DIAGRAMS article.
6. Incorrectly installed or malfunctioning crankcase ventilation valve.
7. Vacuum leaks at throttle body, EGR valve, and intake manifold mounting surfaces.
8. Exhaust leaks. An exhaust leak may cause outside air to be pulled into exhaust gas stream past HO2S 2, causing DTC P0137 to set.
9. MAF sensor. Disconnect MAF sensor harness connector, and see if the condition is corrected. If so, replace MAF sensor.
10. Fuel contamination. Water, even in small amounts, can be delivered to fuel injectors. Water can cause a lean exhaust to be indicated. Excessive alcohol in fuel can also cause this condition.

PCM supplies a bias voltage of about 450 mV between HO2S high signal and low signal circuits. When measured with a 10-megohm DVOM, this may display as low as 320 mV. HO2S varies this voltage within a range of about 1000 mV when exhaust is rich, down through about 10 mV when exhaust is lean. PCM constantly monitors HO2S signal during closed loop operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary. If HO2S 2 voltage remains excessively high for an extended period of time, DTC P0138 will set.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0101, P0102, P0103, P0106, P0107, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
2. Closed loop commanded air/fuel ratio is 12:1-16.5:1.
3. Throttle angle is 3-40 percent.

DTC will set when HO2S 2 signal voltage remains more than 999 mV during normal closed loop operation, or HO2S 2 signal voltage remains more than 200 mV during deceleration fuel mode operation.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Start engine and allow it to reach normal operating temperature. Operate vehicle under conditions required to set DTC. Using scan tool, monitor HO2S 2 voltage. If voltage remains more than 999 mV, go to step 4. If voltage does not remain more than 999 mV, go to next step.
3. Turn ignition on. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for this DTC until DTC test runs. If scan tool indicates test failed this ignition, go to next step. If scan tool does not indicate test failed this ignition, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
4. Disconnect HO2S 2 harness connector. (Scheme 17)or (Scheme 18). Connect a jumper wire between ground and low reference circuit (Tan/White wire) at HO2S 2 harness connector terminal "A". Using scan tool, read HO2S 2 voltage. If voltage is about 450 mV, go to step 8. If voltage is not about 450 mV, go to next step.
5. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Measure voltage between ground and HO2S 2 signal circuit (Purple/White wire) at PCM harness connector C2 terminal No. 11. (Scheme 5)or (Scheme 6). If voltage is more than 999 mV, go to next step. If voltage is not more than 999 mV, go to step 7.
6. Repair short to voltage in signal circuit. After repairs, go to step 9.
7. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to step 9.
8. Replace HO2S 2. After repairs, go to next step.
9. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
10. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Check for the following conditions

1. Fuel pressure. An excessively rich fuel mixture can cause this DTC to set.
2. Rich injectors. See appropriate SYSTEM & COMPONENT TESTING article.
3. EVAP canister. Inspect for fuel saturation. If full of fuel, inspect canister control and hoses.
4. MAF sensor. Disconnect MAF sensor harness connector, and see if rich condition is corrected. If so, replace MAF sensor.
5. Fuel pressure regulator. Check for a leaking fuel pressure regulator diaphragm by checking vacuum line to regulator for presence of fuel. If fuel is present, replace 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. Throttle angle displayed on scan tool should increase steadily from 0 percent to 100 percent when opening throttle. If not, inspect TP sensor for loose mounting screws. If TP mounting screws are okay, replace TP sensor.
7. Shorted HO2S. If HO2S is internally shorted, HO2S voltage displayed on scan tool will be more than one volt. Try disconnecting HO2S and jumper HO2S low circuit to ground with the ignition on. If displayed HO2S voltage changes from more than 1000 mV to around 450 mV, replace HO2S.
8. Silicone contamination of HO2S can also cause a high HO2S voltage to be indicated. This condition is indicated by a powdery White deposit on portion of the HO2S exposed to exhaust stream. If contamination is evident, replace HO2S.
9. Open HO2S high signal or low signal circuit or malfunctioning HO2S. A poor connection or open in HO2S signal or low circuit can cause DTC to set during deceleration fuel mode.
10. An HO2S which is malfunctioning and not allowing a full voltage swing between rich and lean thresholds can also cause this condition. Operate vehicle while monitoring the HO2S voltage with a scan tool. If the HO2S voltage is limited within a range between 300 mV to 600 mV, check HO2S high signal and low signal circuit wiring and associated terminal connections. If wiring and connections are okay, replace HO2S.

PCM supplies a bias voltage of about 450 mV between HO2S signal circuit and low reference circuit. When measured with a 10 megohm DVOM, this voltage may display as low as 350 mV. HO2S signal varies from about 800 mV when exhaust is rich to about 50 mV when exhaust is lean. PCM constantly monitors HO2S signal during closed loop operation. PCM then compensates for a rich or lean condition by decreasing or increasing the pulse width as necessary. If HO2S 2 voltage remains at or near 450 mV bias for an extended period of time, DTC P0140 will set.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0101, P0102, P0103, P0106, P0107, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
2. Engine has been running for at least 4 minutes.
3. System voltage should be 9-18 volts.
4. This test only runs once per trip.
5. TP sensor change of more than 8 percent occurs at least twice during test.

DTC will set when HO2S 2 signal voltage remains between 412 and 500 mV for 90 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, clear DTCs. Reset fuel trim values. Start engine and let it idle until normal operating temperature is reached. Using scan tool, read HO2S 2 voltage. If voltage is 412-500 mV, go to step 4. If voltage is not 412-500 mV, go to next step.
3. The condition that set this DTC is not present. This DTC may have been set by one of the following conditions: HO2S connector water intrusion. Intermittently open HO2S signal circuit. Intermittently open HO2S low circuit. HO2S low circuit with high resistance to ground. High resistance in PCM ground circuits. Inoperative HO2S heater. Poor HO2S or PCM connector terminal contact. An exhaust system leak, typically within 12" upstream of HO2S. Defective HO2S Repair as necessary, then go to step 17. If no problems were found, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect HO2S 2 harness connector. (Scheme 17)or (Scheme 18). Connect a jumper wire between ground and low reference circuit (Tan/White wire) at HO2S 2 harness connector terminal "A". Connect another jumper wire between ground and signal circuit (Purple/White wire) at HO2S 2 harness connector terminal "B". Turn ignition on. Using scan tool, read HO2S 2 voltage. If voltage is less than 20 mV, go to step 7. If voltage is not less than 20 mV, go to next step.
5. Turn ignition off. Remove jumper wires. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Measure resistance of signal circuit (Purple/White wire) between HO2S 2 harness connector terminal "B" and PCM harness connector C2 terminal No. 11. (Scheme 5)or (Scheme 6). Also, check continuity of low reference circuit (Tan/White wire) between HO2S 2 harness connector terminal "A" and PCM harness connector C1 terminal No. 28. If resistance is less than 5 ohms on both circuits, go to next step. If resistance is not less than 5 ohms on both circuits, go to step 9.
6. Inspect PCM harness connector for poor connections. Repair connectors as necessary, then go to step 17. If connectors are okay, go to step 16.
7. Remove jumper wires. Connect a test light between ignition 1 voltage circuit (Brown wire on Alero, Grand Am and Malibu; Pink wire on all other models) at HO2S 2 harness connector terminal "D" and heater ground circuit (Black wire) at HO2S 2 harness connector terminal "C". Start engine. If test light illuminates, go to next step. If test light does not illuminate, go to step 10.
8. Turn ignition off. Reconnect HO2S 2 harness connector. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Measure resistance between low reference circuit (Tan/White wire) at PCM harness connector C1 terminal No. 28 and one of the PCM ground circuit terminals. (Scheme 5)or (Scheme 6). See WIRING DIAGRAMS article. If resistance is less than 500 ohms, go to step 12. If resistance is not less than 500 ohms, go to step 11.
9. Repair circuit with high resistance. After repairs, go to step 17.
10. Repair ignition 1 voltage circuit or heater ground circuit. After repairs, go to step 17.
11. Repair high resistance between low reference circuit and PCM ground circuit. Probable causes are: poor HO2S connector terminal contact, open or high resistance in low reference circuit, poor PCM ground connection, high resistance in PCM ground circuit, or ungrounded exhaust system. After repairs, go to step 17.
12. Check for exhaust system leaks upstream of HO2S 2. Leak may be very small and will typically be within 12" of HO2S. Repair exhaust system as necessary. After repairs, go to step 17.
13. Allow engine to cool to ambient temperature. Again, measure resistance between HO2S low reference circuit (Tan/White wire) at PCM harness connector C1 terminal No. 28 and one of the PCM ground circuit terminals. Operate vehicle within Freeze Frame/Failure Records conditions as noted. If resistance is less than 500 ohms, go to step 15. If resistance is not less than 500 ohms, go to next step.
14. Remove HO2S 2. Clean HO2S mounting threads. Apply Anti-Seize Compound (5613695 or equivalent) to sensor threads. Tighten HO2S to 31 ft. lbs. (42 N.m). Again, measure resistance between low reference circuit (Tan/White wire) at PCM harness connector C1 terminal No. 28 and one of the PCM ground circuit terminals. If resistance is less than 500 ohms, go to step 17. If resistance is not less than 500 ohms, go to next step.
15. Replace HO2S 2. After repairs, go to step 17.
16. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
17. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
18. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Heated Oxygen Sensors (HO2S) are used in order to minimize time required for closed loop fuel control operation and to allow accurate catalyst monitoring. HO2S heater greatly decreases time required for fuel control sensor HO2S 1 to become active. HO2S heater is required by catalyst monitor sensor HO2S 2 to maintain a sufficiently high temperature. This allows accurate exhaust oxygen content readings further from engine.

PCM will run heater test only after a cold start (determined by engine coolant temperature and intake air temperature at time of start-up) and will test only once during an ignition cycle. When engine is started, PCM will monitor HO2S voltage. When HO2S voltage indicates a sufficiently active sensor, PCM determines how much time has elapsed since start-up. If PCM determines that too much time was required for HO2S 2 to become active, DTC P0141 will set. The time HO2S needs to reach operating temperature is based on engine coolant temperature at start-up and average mass airflow since start-up. A higher average airflow or higher start-up engine coolant temperature means less time to HO2S activity.

PCM will run diagnostic for this DTC under the following conditions

1. DTC P0101, P0102, P0103, P0106, P0107, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
2. System voltage is 9-18 volts.
3. Intake Air Temperature (IAT) and Engine Coolant Temperature (ECT) are less than 95°F (35°C) at start-up.
4. IAT and ECT are within 10°F of each other at start-up.

DTC will set when HO2S 2 voltage remains within 150 mV of bias voltage (about 450 mV) for a longer time than it should. The time ranges from 100 to 130 seconds, depending on engine coolant temperature at start-up and average airflow since start-up.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step. NOTE: If engine has been operating, allow engine to cool for about 30 minutes before proceeding with test.
2. Turn ignition on, engine off. Using scan tool, read HO2S 2 voltage. If voltage goes from bias voltage (about 450 mV) to more than 600 mV or to less than 300 mV, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM. If voltage does not go from bias voltage (about 450 mV) to more than 600 mV or to less than 300 mV, go to next step.
3. On Century, Impala and Monte Carlo, check OXY SEN fuse (15-amp). On Grand Prix, check IGN1-UH fuse (15-amp). On Alero, Grand Am and Malibu, check ERLS fuse (10-amp). On all models, fuses are located in underhood fuse block. If fuse is open, go to step 15. If fuse is okay, go to next step.
4. Disconnect HO2S 2 harness connector. (Scheme 17)or (Scheme 18). Connect a test light between ground and ignition 1 voltage circuit (Brown wire on Alero, Grand Am and Malibu; Pink wire on all other models) at HO2S 2 harness connector terminal "D". If test light illuminates, go to next step. If test light does not illuminate, go to step 7.
5. Connect test light between heater ground circuit (Black wire) at HO2S 2 harness connector terminal "C" and ignition 1 voltage circuit (Brown wire on Alero, Grand Am and Malibu; Pink wire on all other models) at HO2S 2 harness connector terminal "D". If test light illuminates, go to next step. If test light does not illuminate, go to step 8.
6. Allow HO2S 2 to cool for at least 10 minutes. Measure resistance between HO2S 2 terminals "C" and "D" (component side). If resistance is 4-6 ohms, go to step 9. If resistance is not 4-6 ohms, go to step 14.
7. Repair open in ignition 1 voltage circuit (Brown wire on Alero, Grand Am and Malibu; Pink wire on all other models) between HO2S 2 and underhood fuse block. See WIRING DIAGRAMS article. After repairs, go to step 16.
8. Repair open in HO2S 2 heater ground circuit (Black wire) between HO2S 2 and ground point located near starter. After repairs, go to step 16.
9. Check for faulty connection at HO2S 2. Repair connector as necessary, then go to step 16. If connection is okay, go to next step.
10. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Measure resistance of signal circuit (Purple/White wire) between HO2S 2 harness connector terminal "B" and PCM harness connector C2 terminal No. 11. (Scheme 5)or (Scheme 6). Also, measure resistance of low reference circuit (Tan/White wire) between HO2S 2 harness connector terminal "A" and PCM harness connector C1 terminal No. 28. If resistance on either circuit is more than 5 ohms, repair open or faulty connection as necessary. After repairs, go to step 16. If resistance is 5 ohms or less on both circuits, go to next step.
11. Check for faulty connection at HO2S 2 harness connector. Repair connector as necessary, then go to step 16. If connection is okay, go to next step.
12. Check for faulty HO2S 2 ground circuit connection at PCM. Repair connector as necessary, then go to step 16. If connection is okay, go to next step.
13. Check for faulty HO2S 2 signal circuit connection at PCM. Repair connector as necessary, then go to step 16. If connection is okay, go to next step.
14. Replace HO2S 2. After repairs, go to step 16.
15. Locate and repair short to ground in ignition 1 voltage circuit (Brown wire on Alero, Grand Am and Malibu; Pink wire on all other models) between HO2S 2 and underhood fuse block. See WIRING DIAGRAMS article. Replace fuse. After repairs, go to next step.
16. Allow engine to cool completely. Using scan tool, clear DTCs. Turn ignition on, engine off. Read HO2S 2 voltage. If voltage is greater than 600 mV or less than 300 mV, system is okay. If voltage is not greater than 600 mV or not less than 300 mV, go to step 2.
17. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

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). If oxygen sensors indicate a lean condition, fuel trim values will be more than zero percent. If oxygen sensors indicate a rich condition, fuel trim values will be less than zero percent. 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 an air/fuel ratio of 14.7:1. If PCM detects an excessively lean condition, this DTC will set.

PCM will run diagnostic for this DTC under the following conditions

1. DTC P0101, P0102, P0103, P0107, P0108, P0121, P0122, P0123, P0130, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0401, P0403, P0404, P0405, P0410, P0440, P0442, P0446, P0506, P0507, P1404, or P1441 are not set.
2. Engine Coolant Temperature (ECT) is 68-230°F (20-110°C).
3. Intake Air Temperature (IAT) is 64-158°F (18-70°C).
4. Manifold Absolute Pressure (MAP) is 2.1-15.2 psi (15-105 kPa).
5. Vehicle speed is less than 82 MPH.
6. Engine speed is 550-4000 RPM.
7. Barometric Pressure (BARO) is more than 10.1 psi (70 kPa).
8. Mass Airflow (MAF) is 2.8-150.0 grams per second.
9. Fuel level is more than 10 percent.

DTC will set when average long term fuel trim value is more than 20 percent and all of the above conditions are present for 6 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Start engine and let it idle at normal operating temperature in closed loop. Using scan tool, read and record LONG TERM FUEL TRIM. Turn engine off. Turn ignition on. Using scan tool, review FREEZE FRAME/FAILURE RECORDS, and record displayed data for this DTC. If LONG TERM FUEL TRIM is more than 23 percent, go to next step. If LONG TERM FUEL TRIM is not more than 23 percent, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) .
3. Start engine and let it idle. Using scan tool, read HO2S voltage parameters. If voltage is fluctuating between 200 and 800 mV, go to next step. If voltage is not fluctuating between 200 and 800 mV, go to step 5 .
4. Turn engine off. Check vacuum hoses for splits, kinks, and proper connections. See VACUUM DIAGRAMS - CARS article. Ensure vehicle has sufficient fuel in tank. Ensure fuel is not contaminated. If a problem is found, repair as necessary, then go to step 7 . If no problem is found, go to step 6 .
5. Check HO2S 1 for proper installation. Ensure HO2S 1 wires are secure and not contacting exhaust system. Check for a short between HO2S 1 signal circuit and low reference circuit. If a problem is found, repair as necessary. After repairs, go to step 7 . If no problems were found, check fuel system and repair as necessary. See appropriate BASIC DIAGNOSTIC PROCEDURES article.
6. Start engine and let it idle. Check for the following conditions: Check for missing, loose or leaking exhaust components upstream of HO2S 1. Check for vacuum leaks at intake manifold, throttle body and injector "O" rings. Check air induction system and air intake ducts for leaks. Check air injection system for leaks or improper air delivery. Ensure shut-off valve is closing. Check crankcase ventilation system for leaks. If a problem is found, repair as necessary. After repairs, go to next step. If no problems were found, check for engine mechanical problems. Repair as necessary. NOTE: After making repairs, use scan tool to reset long term fuel trim.
7. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2 . If DTC does not reset, go to next step.
8. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs, system is okay.

System will go lean if an injector is not supplying enough fuel. A lean condition could be present during high fuel demand due to a pump that does not pump enough fuel. Fuel contamination, such as water and alcohol, will effect fuel trim. Use a scan tool in order to review Failure Records. If an intermittent condition is suspected, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

During closed loop, Heated Oxygen Sensor (HO2S) 1 input is used by PCM to calculate short and long term fuel trim (fuel delivery adjustments). If HO2S 1 indicates a lean condition, fuel trim values will be more than zero percent. If HO2S 1 indicates a rich condition, fuel trim values will be less than zero percent. Short term fuel trim values change rapidly in response to HO2S 1 signals. Long term fuel trim makes coarse adjustments in order to maintain a 14.7:1 air/fuel ratio.

PCM will conduct a test to determine if a rich failure actually exists or if excessive vapor from EVAP canister is causing a rich condition. If PCM detects an excessively rich condition, this DTC will set. If PCM detects excessive vapor, test will pass.

PCM will run diagnostic for this DTC under the following conditions

1. DTC P0101, P0102, P0103, P0107, P0108, P0121, P0122, P0123, P0130, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0120, P0122, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0401, P0403, P0404, P0405, P0410, P0412, P0418, P0440, P0442, P0446, P0506, P0507, P1404 or P1441 are not set.
2. Engine Coolant Temperature (ECT) is 68-230°F (20-110°C).
3. Intake Air Temperature (IAT) is 64-158°F (18-70°C).
4. Manifold Absolute Pressure (MAP) is 2.1-15.2 psi (15-105 kPa).
5. Vehicle speed is less than 82 MPH.
6. Engine speed is 550-4000 RPM.
7. Barometric pressure is more than 10.1 psi (70 kPa).
8. Mass Airflow (MAF) is 2.8-150.0 grams per second.
9. Fuel level is more than 10 percent.

DTC will set when average long term fuel trim value is less than -13 percent for 40 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Start engine and warm to normal operating temperature. Allow engine to idle in closed loop. Using scan tool, read and record long term fuel trim data. Turn ignition off then on. Using scan tool, review FREEZE FRAME/FAILURE RECORDS for this DTC. If scan tool indicates that long term fuel trim is less than -13 percent, go to next step. If scan tool does not indicate that long term fuel trim is less than -13 percent, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) .
3. Start engine and let it idle. Using scan tool, read HO2S voltage. If voltage is fluctuating between 200 and 800 mV, go to next step. If voltage is not fluctuating between 200 and 800 mV, go to step 5 .
4. Turn engine off. Check the following items: MAF sensor inlet screen for blockage. Vacuum hoses for splits, kinks and proper connections. See VACUUM DIAGRAMS - CARS article. Air intake duct for being collapsed or restricted. Air filter for being dirty or restricted. Check for objects blocking throttle body.
5. Turn engine off. Check HO2S 1 for proper installation. Ensure HO2S 1 harness connector and wires are secure and not contacting exhaust system. If a problem is found, repair as necessary, then go to step 7 . If no problems are found, diagnose fuel system. See appropriate BASIC DIAGNOSTIC PROCEDURES article.
6. Check the following: Check for excessive fuel in crankcase. Inspect EVAP control system. Check fuel pressure regulator for proper operation. See appropriate BASIC DIAGNOSTIC PROCEDURES article. Ensure that all injectors are functioning properly. See appropriate SYSTEM & COMPONENT TESTING article. Perform fuel injector balance test with scan tool. If a problem is found, repair as necessary, then go to next step. If no problems are found, diagnose engine mechanical problem.
7. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2 . If DTC does not reset, go to next step.
8. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs, system is okay.

Fuel contamination, such as water and alcohol will effect fuel trim. A malfunctioning MAF sensor can cause a rich condition and set this DTC. See DTC P0101: MAF SYSTEM PERFORMANCE (CENTURY, GRAND PRIX & MALIBU) . If an intermittent condition is suspected, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

PCM enables appropriate fuel injector on intake stroke for each cylinder. A voltage is supplied directly 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.

PCM will run diagnostic for these DTCs under the following conditions

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

DTC will set when PCM detects an incorrect voltage on injector control circuit for 30 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, clear DTCs. Start engine and warm to normal operating temperature. Allow engine to idle. Using scan tool, monitor 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. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. If scan tool indicates that this DTC FAILED THIS IGN, go to next step. If scan tool does not indicate that this DTC FAILED THIS IGN, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
4. Turn ignition off. Disconnect Black, 16-pin in-line harness connector located in right rear of engine compartment. Connect a test light between battery positive and appropriate injector control circuit at in-line harness connector (PCM side). See «INJECTOR CONTROL CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table. (Scheme 19) Crank engine. If test light flashes, go to step 8. If test light does not flash, go to next step.
5. If test light remains illuminated at all times, go to step 7. If test light does not remain illuminated at all times, go to next step.
6. Check for open or short to voltage in appropriate injector control circuit between in-line harness connector and PCM. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 18. If circuit is okay, go to step 14.
7. Check for short to ground in appropriate injector control circuit between in-line harness connector and PCM. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 18. If circuit is okay, go to step 17.
8. Inspect accessible fuel injector harness between in-line harness connector and intake plenum for the following: Poor connections at in-line harness connector. Damaged or pinched wiring. Broken wires inside insulation. If a problem is found, repair as necessary, then go to step 18. If no problem is found, go to next step.
9. Remove upper intake plenum. See appropriate article in ENGINES. Connect a test light between battery positive and appropriate injector control circuit at in-line harness connector (injector side). If test light illuminates, go to step 15. If test light does not illuminate, go to next step.
10. Measure resistance between ignition voltage circuit (Pink wire) at in-line harness connector terminal "A" and appropriate injector control circuit at in-line harness connector (injector side). If resistance is infinite, go to next step. If resistance is not infinite, go to step 13.
11. Check for open in appropriate injector control circuit between injector and in-line harness connector. Also, check for poor connections at appropriate injector. If a problem is found, repair as necessary, then go to step 18. If no problem is found, go to next step.
12. Check for open in ignition voltage circuit (Pink wire) between appropriate injector and splice. On Alero, Grand Am and Malibu, splice is located about 6" from in-line harness connector. On all other models, splice is located near injector No. 2 breakout. On all models, repair circuit as necessary, then go to step 18. If no problem is found, go to step 16.
13. Check for short to voltage or short to another circuit in appropriate injector control circuit. Repair circuit as necessary, then go to step 18. If circuit is okay, go to step 16.
14. Check for poor connections at PCM harness connectors. Repair connector(s) as necessary, then go to step 18. If connectors are okay, go to step 17.
15. Repair short to ground in appropriate injector control circuit. After repairs, go to step 18.
16. Replace appropriate fuel injector. After repairs, go to step 18.
17. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
18. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
19. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

INJECTOR CONTROL CIRCUIT IDENTIFICATION

Scheme 19

Performing injector coil test may help isolate an intermittent condition. See appropriate SYSTEM & COMPONENT TESTING article. If condition is intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

PCM provides ignition positive voltage to coil side of fuel pump relay. When ignition is first turned on, PCM energizes fuel pump relay, which applies power to fuel pump. PCM enables fuel pump relay as long as engine is cranking or running, and crankshaft reference pulses are received. If no crankshaft reference pulses are received, PCM de-energizes fuel pump relay after 2 seconds. PCM monitors voltage on fuel pump relay control circuit. If PCM detects an incorrect voltage on fuel pump relay control circuit, DTC P0230 sets.

PCM will run diagnostic for this DTC under the following conditions

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

DTC will set when PCM detects an incorrect voltage on fuel pump relay control circuit for less than one second.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, command fuel pump relay on and off. Fuel pump relay is located in underhood fuse block. If fuel pump relay turns on and off with each command, go to next step. If fuel pump relay does not turn on and off with each command, go to step 4.
3. Using scan tool, read and record FAILURE RECORDS data. Turn ignition off and wait 30 seconds. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays that this DTC FAILED THIS IGN, go to next step. If scan tool does not display that this DTC FAILED THIS IGN, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect fuel pump relay. Turn ignition on. Connect a test light between ground and control circuit (Dark Green/White wire) at fuel pump relay harness connector. Using scan tool, command fuel pump relay on and off. If test light turns on and off with each command, go to next step. If test light does not turn on and off with each command, go to step 6.
5. Connect test light between control circuit (Dark Green/White wire) and ground circuit (Black wire on Alero, Grand Am and Malibu; Black/White wire on all other models) at fuel pump relay harness connector. Using scan tool, command fuel pump relay 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 step 11.
6. If test light remains illuminated with each command, go to step 8. If test light does not remain illuminated with each command, go to next step.
7. Check for open or short to ground in control circuit (Dark Green/White wire) between fuel pump relay harness connector and PCM harness connector C2 terminal No. 3. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 14. If circuit is okay, go to step 10.
8. Check for short to voltage in control circuit (Dark Green/White wire) between fuel pump relay harness connector and PCM harness connector C2 terminal No. 3. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 14. If circuit is okay, go to step 10.
9. Check for faulty connections at fuel pump relay harness connector. Repair connector as necessary, then go to step 14. If connector is okay, go to step 12.
10. Check for faulty connections at PCM harness connector. Repair connector as necessary, then go to step 14. If connector is okay, go to step 13.
11. Repair open in fuel pump relay ground circuit (Black wire on Alero, Grand Am and Malibu; Black/White wire on all other models) between fuel pump relay harness connector and ground. See WIRING DIAGRAMS article for ground point location. After repairs, go to step 14.
12. Replace fuel pump relay. After repairs, go to step 14.
13. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
14. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
15. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

PCM uses information from Ignition Control (IC) module and Camshaft Position (CMP) sensor 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 three-way catalytic converter to overheat under certain conditions. MIL will flash when conditions for three-way catalytic converter overheating are present.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0101, P0102, P0103, P0107, P0108, P0117, P0118, P0121, P0122, P0123, P0125, P0336, P0341, P0502, P0503, P1106, P1107, P1114, P1115, P1121, P1122, P1336, P1351, P1352, P1361, P1362, or P1374 are not set.
2. Engine speed is 525-5900 RPM.
3. System voltage is 9-18 volts.
4. Engine coolant temperature is 21-255°F (-7-125°C).
5. Throttle angle is steady.

DTC will set when The 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»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Check for other DTCs. If other DTCs are also set, diagnose those DTCs first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If no other DTCs are set, go to next step.
3. Start engine and let it idle. Using scan tool, read and record FREEZE FRAME data. Operate vehicle within conditions noted in FREEZE FRAME data. Using scan tool, read MISFIRE CUR # display for each cylinder. If MISFIRE CUR # is increasing (indicating a misfire currently occurring) for any cylinder, go to step 5 . If MISFIRE CUR # is not increasing, go to next step.
4. View MISFIRE HIST # on scan tool. If MISFIRE HIST # displays a very large value for more than one cylinder, go to next step. If MISFIRE HIST # does not display a very large value for more than one cylinder, go to step 8 .
5. If misfire values displayed on MISFIRE HIST # are related to companion cylinders (i.e., 1/4, 2/5, 3/6), go to step 9 . If misfire values displayed are not companion cylinders, go to next step.
6. Check the following items: Excessive vibration from sources other than engine. Drive belts. Vacuum hoses. See VACUUM DIAGRAMS - CARS article. Crankcase ventilation system for vacuum leaks. Throttle body and intake manifold for vacuum leaks. PCM grounds. See WIRING DIAGRAMS article. Spark plug wires. Measure the resistance of spark plug wires associated with misfiring cylinders. Resistance should be 3000 ohms per foot. EGR valve-to-exhaust manifold pipe for proper connections and signs of damage. Fuel for contamination. If a problem is found, repair as necessary, then go to step 18 . If no problems were found, go to next step.
7. Check fuel pressure. If fuel pressure is 52-59 psi (358-405 kPa), go to next step. If fuel pressure is not 52-59 psi (358-405 kPa), diagnose fuel system. See FUEL SYSTEMS (GASOLINE) in appropriate SYSTEM & COMPONENT TESTING article.
8. Check for proper injector operation. See FUEL SYSTEMS (GASOLINE) in appropriate SYSTEM & COMPONENT TESTING article. If a problem is found, repair as necessary. After repairs, go to step 18 . If no problem is found, go to next step.
9. Check ignition wire(s) and coil(s) associated with misfiring cylinder(s) for carbon tracking, arching, poor connections or improper connections. If a problem is found, repair as necessary. After repairs, go to step 18 . If no problem is found, go to next step.
10. Install a spark tester on spark plug wire at spark plug end for cylinder indicating most severe misfire. Connect a jumper wire between engine ground and companion cylinder spark plug wire at spark plug end. Companion cylinders are 1/4, 2/5, and 3/6. Crank engine and check for spark at tester. Repeat procedure for each affected cylinder. If spark is okay on all cylinders, go to step 15 . If spark is not okay on any cylinder, go to next step.
11. Measure resistance of ignition wires associated with misfiring cylinders. Resistance should be about 600 ohms per foot. Replace as necessary. After replacing ignition wire(s), go to step 18 . If ignition wires are okay, go to next step.
12. Measure resistance of secondary ignition coils associated with misfiring cylinders. Resistance should be 5000-8000 ohms. If resistance is as specified, go to step 18 . If resistance is not as specified, go to next step.
13. Remove ignition coil(s) associated with misfiring cylinder(s). Check ignition coils for cracks or carbon tracking, cracks or other damage. If a problem is found, replace damaged coil(s). After repairs, go to step 18 . If no problem is found, go to next step.
14. Leave ignition coils disconnected. Connect a test light between ignition module primary circuit terminals. Remove fuel injector fuse. Crank engine. Observe test light. If test light flashes, go to step 16 . If test light does not flash, go to step 17 .
15. Remove spark plug(s) associated with misfiring cylinder(s). Check spark plugs for excessive fouling. If spark plugs are excessively fouled, diagnose and repair mechanical engine problem. After repairs, go to step 18 . If spark plugs are not excessively fouled, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) .
16. Replace ignition coils associated with misfiring cylinders. After replacing coils, go to step 18 .
17. Replace ignition control module. After replacing module, go to next step.
18. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2 . If DTC does not reset, go to next step.
19. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs, system is okay.

Scan tool will indicate if a test has failed since codes have been cleared. Misfire history will be stored and displayed for each of the cylinders at time of failure. Incorrect rough road signal may have been received from Electronic Brake Control Module (EBCM) or Electronic Brake Traction Control Module (EBTCM). Crankshaft Position (CKP) system variation learn procedure must be performed if any of the following conditions are true

1. PCM has been replaced.
2. DTC P1336 is set.
3. Engine has been replaced.
4. Crankshaft or crankshaft balancer has been replaced.
5. CKP sensor has been replaced.

For procedure, see COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION. If condition is intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

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 KS and related wiring by comparing actual knock signal to assigned voltage range. A normal KS signal should stay outside assigned voltage range. DTC P0325 will set if PCM malfunctions in a manner that will not allow proper diagnosis of KS system and related wiring.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0101, P0102, P0103, P0107, P0108, P0117, P0118, P0121, P0122, P0123, P0125, P0336, P1114, P1115, P1121, P1122 P1336 are not set.
2. Engine speed is 1000-5000 RPM.
3. Throttle angle is more than 15 percent.
4. Engine load is more than 40 percent.
5. Engine coolant temperature is more than 153°F (60°C).
6. Maximum spark retard is less than 15 degrees.
7. System voltage is more than 9 volts.
8. Engine run time is more than 30 seconds.

DTC will set when PCM detects a malfunction in integrated knock sensor diagnostic circuitry which will not allow proper diagnosis of knock sensor circuit for at least one second.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Read and record FAILURE RECORDS data for this DTC. Turn ignition off and wait 30 seconds. Start engine and operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool indicates that this DTC FAILED THIS IGN, go to next step. If scan tool does not indicate that this DTC FAILED THIS IGN, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
3. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . After replacing PCM, go to next step.
4. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2 . If DTC does not reset, go to next step.
5. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs, system is okay.

PCM contains integrated Knock Sensor (KS) diagnostic circuitry. 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 KS and related wiring by comparing actual knock signal to assigned voltage range. A normal KS signal should stay outside assigned voltage range. DTC P0327 will set if KS signal is within assigned voltage range or if KS signal is not present.

PCM will run diagnostic for this DTC under the following conditions

1. DTC P0112, P0113, P0121, P0122, P0123, P0341, P0336, P0506 or P0507 are not set.
2. Engine speed is 1000-5000 RPM.
3. Engine has been running for a minimum of 30 seconds.
4. Throttle angle is more than 15 percent.
5. Engine load is more than 40 percent.
6. Engine coolant temperature is more than 153°F (60°C).
7. Maximum spark retard is less than 15 degrees.
8. System voltage is more than 9 volts.

DTC will set when PCM detects a KS signal voltage within calculated average voltage range for at least 10 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, monitor 24X CRANK SENSOR and CAM signals. If 24X CRANK SENSOR and CAM signals are present, go to next step. If 24X CRANK SENSOR and CAM signals are not present, see «DTC P0336: CRANKSHAFT POSITION SENSOR CIRCUIT»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
3. Turn ignition on. Using scan tool, read FAILURE RECORDS data for DTC P0327. Turn ignition off and wait 30 seconds. Operate vehicle within FAIL RECORDS conditions. Using a scan tool, monitor SPECIFIC DTC info for this DTC until DTC test runs. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed this ignition cycle, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect KS harness connector. (Scheme 20)or (Scheme 21). Turn ignition on. Measure voltage between ground and signal circuit (Dark Blue wire) at KS harness connector. If voltage is about zero volts, go to step 6. If voltage is not about zero volts, go to next step.
5. Repair short to voltage in signal circuit. After repairs, go to step 10.
6. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Check for open or short to ground in signal circuit (Dark Blue wire) between knock sensor harness connector and PCM harness connector C1 terminal No. 33. (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 10. If circuit is okay, go to next step.
7. Check for poor connection at KS harness connector. Repair connector as necessary, then go to step 10. If connector is okay, go to next step.
8. Check for poor connection at PCM harness connector. Repair connector as necessary, then go to step 10. If connector is okay, go to next step.
9. Replace KS. After repair, go to next step.
10. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
11. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Scheme 20

Scheme 21

Circuit uses 2 different types of Crankshaft Position (CKP) sensors. The 7X CKP sensor is connected directly to Ignition Control (IC) module, and consists of a CKP 1 sensor signal circuit and a low reference circuit. The 24X CKP sensor connects directly to PCM, and consists of a 12-volt reference circuit, a medium resolution engine speed signal circuit and a low reference circuit.

PCM will run diagnostic for this DTC when engine is running and 3X reference pulses are being received for a minimum of 3 seconds. DTC P0336 will set when ratio of 24X reference pulses to 3X reference pulses received by PCM is incorrect.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Start engine. Using scan tool, observe 24X RPM. If 24X RPM varies with engine speed up to about 1600 RPM, go to next step. If 24X RPM does not vary with engine speed up to about 1600 RPM, go to step 4.
3. Using scan tool, observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off. Start engine. Operate vehicle under conditions for setting DTC or as close to FREEZE FRAME/FAILURE RECORDS data. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed this ignition cycle, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
4. Turn ignition off. Disconnect 24X CKP sensor harness connector. (Scheme 20)or (Scheme 21). Turn ignition on. Measure voltage between ground and 12-volt reference circuit (Red/White wire on Alero and Grand Am; Light Green wire on all other models) at 24X CKP sensor harness connector terminal "A". If battery voltage exists, go to step 6. If battery voltage does not exist, go to next step.
5. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Check for open or short to ground in 12-volt reference circuit (Red/White wire on Alero and Grand Am; Light Green wire on all other models) between 24X CKP sensor harness connector terminal "A" and PCM harness connector C2 terminal No. 70. (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 16. If circuit is okay, go to step 12.
6. Connect a test light between battery voltage and low reference circuit (Yellow/Black wire) at 24X CKP sensor harness connector terminal "C". If test light illuminates, go to step 8. If test light does not illuminate, go to next step.
7. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Check for open in low reference circuit (Black wire on Alero and Grand Am; Yellow Black wire on all other models) between 24X CKP sensor harness connector terminal "C" and PCM harness connector C2 terminal No. 74. (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 16. If circuit is okay, go to step 12.
8. Using scan tool, monitor 24X RPM. Using a 5-amp fused jumper wire connected to battery voltage, momentarily touch medium resolution engine speed signal circuit (Light Blue/Black wire) at 24X CKP sensor harness connector terminal "B" 5 times for one second each time. If 24X RPM changes each time signal circuit is touched, go to step 13. If 24X RPM does not change each time the signal circuit is touched, go to next step.
9. Check fuse in jumper wire. If fuse is open, go to step 11. If fuse is okay, go to next step.
10. Check for open or short to voltage in medium resolution engine speed signal circuit (Light Blue/Black wire) between 24X CKP sensor harness connector terminal "B" and PCM harness connector C1 terminal No. 9. Repair circuit as necessary, then go to step 16. If circuit is okay, go to step 12.
11. Check for short to ground in medium resolution engine speed signal circuit (Light Blue/Black wire) at 24X CKP sensor harness connector terminal "B". Repair circuit as necessary, then go to step 16. If circuit is okay, go to next step.
12. Check for poor connections at PCM. Repair connector as necessary. After repairs, go to step 16. If connections are okay, go to step 14.
13. Check for poor connections at 24X CKP sensor. Repair as necessary. After repairs, go to step 16. If connections are okay, go to step 15.
14. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to step 16.
15. Replace 24X CKP sensor. After replacing sensor, go to next step.
16. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
17. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

DTC P0336 can be caused by secondary components leaking high voltage into ignition control module. Inspect for the following conditions

1. Incorrect harness routing near secondary ignition components.
2. Ignition coil arcing to wiring harness or IC module. Inspect ignition coils for cracks, carbon tracking or other signs of damage.
3. Secondary ignition wires arcing to wiring harness.

If DTC is determined to be intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

During cranking, Ignition Control (IC) Module monitors 7X crankshaft position sensor signal. Once IC module determines spark synchronization, 3X reference signals are sent to PCM. PCM will command all six injectors on for one priming shot of fuel in all cylinders. After priming, injectors are left off for next six fuel control reference signals (two crankshaft revolutions). This allow each cylinder a chance to use fuel from the priming shot. During this waiting period, a Camshaft Position (CMP) sensor pulse will have been received by PCM. PCM uses Cam signal pulses to initiate sequential fuel injection.

PCM constantly monitors number of pulses on Cam signal circuit and compares number of Cam pulses to number of 24X reference pulses and number of 3X reference pulses being received. If PCM receives an incorrect number of pulses on Cam reference circuit, DTC P0341 will set and PCM will initiate injector sequence without Cam signal with a one in six chance that injector sequence is correct. The engine will continue to start and run normally, although misfire diagnostic will be affected if a misfiring condition occurs.

PCM will run diagnostic for this DTC when engine is running (3X reference pulses are being received). DTC will set when CMP sensor reference pulse is not detected on every engine cycle.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Start engine. Using scan tool, observe CMP sensor signal. If scan tool indicates that CMP sensor signal is present, go to next step. If scan tool does not indicate that CMP sensor signal is present, go to step 4.
3. Using scan tool, observe FREEZE FRAME/FAILURE RECORDS data. Turn ignition off and wait 30 seconds. Start engine and operate vehicle under conditions required to set DTC or close to conditions noted in FREEZE FRAME/FAILURE RECORDS data. If scan tool indicates that this DTC failed this ignition, go to next step. If scan tool does not indicate that this DTC failed this ignition, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
4. Turn ignition off. Disconnect CMP sensor harness connector. (Scheme 21)or (Scheme 22). Turn ignition on. Measure voltage between ground and 12-volt reference circuit (Red/White wire) at CMP sensor harness connector terminal "A". If battery voltage exists, go to step 6. If battery voltage does not exist, go to next step.
5. Turn ignition off. Disconnect PCM harness connector C2. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Check for open or short to ground in 12-volt reference circuit (Red/White wire) between CMP sensor harness connector terminal "A" and PCM harness connector C2 terminal No. 72. (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 16. If circuit is okay, go to step 12.
6. Connect a test light between battery positive and sensor ground circuit (Black wire) at CMP sensor harness connector terminal "C". If test light illuminates, go to step 8. If test light does not illuminate, go to next step.
7. Turn ignition off. Disconnect PCM harness connector C2. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Check for open in sensor ground circuit (Black wire) between CMP sensor harness connector terminal "C" and PCM harness connector C2 terminal No. 73. (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 16. If circuit is okay, go to step 12.
8. Start engine. Using scan tool, monitor CMP sensor signal. Using a 5-amp fused jumper wire connected to battery voltage, momentarily touch signal circuit (Black/White wire on Grand Prix; Brown/White wire on all other models) at CMP sensor harness connector terminal "B" 5 times for about one second each time. If CMP sensor signal changes each time the signal circuit is touched, go to step 14. If CAM signal does not change each time the signal circuit is touched, go to next step.
9. Check fuse in jumper wire. If fuse is open, go to step 11. If fuse is okay, go to next step.
10. Check for open or short to voltage in signal circuit (Black/White wire on Grand Prix; Brown/White wire on all other models) between CMP sensor harness connector terminal "B" and PCM harness connector C1 terminal No. 7. Repair circuit as necessary, then go to step 16. If circuit is okay, go to step 12.
11. Check for short to ground in signal circuit (Black/White wire on Grand Prix; Brown/White wire on all other models) between CMP sensor harness connector terminal "B" and PCM harness connector C1 terminal No. 7. Repair circuit as necessary, then go to step 16. If circuit is okay, go to next step.
12. Check for poor connections at PCM. Repair connector as necessary, then go to step 16. If connections are okay, go to next step.
13. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to step 16.
14. Check for poor connections at CMP sensor. Repair connector as necessary, then go to step 16. If connections are okay, go to next step.
15. Replace CMP sensor. After replacing sensor, go to next step.
16. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
17. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Scheme 22

Check for incorrect harness routing near secondary ignition components, ignition coil arcing to wiring harness or IC module. Check ignition coils for cracks, carbon tracking or other signs of damage. Check for secondary ignition wire(s) arcing to wiring harness.

Check for faulty connections or damaged harness. Observe a voltmeter connected to CMP sensor signal circuit at PCM harness connector while moving all related harness and connectors. A change in voltage indicates fault location. If condition is intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

PCM tests EGR system during deceleration by momentarily commanding EGR valve to open while monitoring Manifold Absolute Pressure (MAP) sensor signal. When EGR valve is opened, PCM should see a proportional increase in MAP. If expected increase in MAP is not seen, PCM notes the amount of error that was detected and adjusts an internal fail counter towards a fail threshold level. When fail counter exceeds fail threshold level, PCM will set this DTC. The number of test samples required to accomplish this may vary according to amount of detected flow error. Normally, PCM will only allow one EGR flow test sample to be taken during an ignition cycle. To aid in verifying a repair, PCM allows 12 test samples during first ignition cycle following a scan tool Clear Info or a battery disconnect. Between 9 and 12 samples should be sufficient for PCM to determine adequate EGR flow and pass EGR test.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0201-P0206, P0300, P0336, P0403, P0404, P0502, P0503, P0506, P0507, P1106, P1107, P1111, P1112, P1114, P1115. P1121, P1122, P1374 or P1404 are not set.
2. System voltage is 10-18 volts.
3. A/C status does not change.
4. Transaxle range does not change.
5. Throttle angle is less than one percent (deceleration).
6. Intake air temperature is more than 176°F (80°C).
7. Engine coolant temperature is more than 167°F (75°C).
8. Engine speed is 1050-1300 RPM.
9. Idle Air Control (IAC) position is steady.
10. MAP is steady at 15-70 kPa.
11. Vehicle speed is more than 35 MPH during deceleration.
12. Barometric pressure is more than 70 kPa.
13. Drive vehicle at a speed of more than 50 MPH, then allow vehicle to decelerate. When vehicle is decelerating while meeting all criteria listed above, PCM will enable test to run. As test is running, you will see DESIRED EGR parameter and EGR POSITION SENSOR on scan tool change from zero to a calibrated value more than zero.

DTC will set when MAP changes monitored during EGR flow test indicate insufficient EGR flow.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. If any MAP DTCs are set, diagnose and repair MAP DTC(s) first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If no MAP DTCs are set, go to next step.
3. Inspect exhaust system for modification of original installed parts or leaks. Repair exhaust system as necessary, then go to step 7 . If exhaust system is okay, go to next step.
4. Check EGR valve gasket and pipe for leaks. Repair EGR system as necessary, then go to step 7 . If EGR system is okay, go to next step.
5. Remove EGR valve. Inspect EGR valve pintle and EGR valve passages for leak or restriction. Clean or repair EGR valve as necessary, then go to step 7 . If EGR valve is okay, go to next step.
6. Remove EGR inlet pipe from exhaust manifold. Inspect manifold EGR ports and EGR inlet pipe for a blockage caused by excessive deposits or other damage. If a problem is found, repair as necessary, then go to next step. If no problems were found, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) .
7. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2 . If DTC does not reset, go to next step.
8. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs, system is okay.

Inspect for the following conditions

1. A vacuum restriction to MAP sensor. A restriction to MAP sensor can cause EGR flow test to fail due to insufficient MAP changes being monitored during test. Inspect for objects blocking vacuum to MAP sensor.
2. An engine that is running poorly may cause this DTC to set.
3. Poor connections or a damaged harness. Inspect wiring harness for damage.
4. If harness appears okay, observe EGR POSITION SENSOR display on scan tool while moving connectors and wiring harnesses related to EGR valve. A change in display indicates location of malfunction.

In order to verify a repair, clear info using scan tool and run EGR flow test keeping the following items in mind

1. PCM will only run EGR flow test during a gradual deceleration with throttle closed and vehicle speed more than 35 MPH.
2. Several deceleration cycles, typically 9-12, will be necessary in order to run a sufficient number of EGR flow test samples.
3. EGR TEST COUNTER displayed on scan tool can be useful in determining that EGR flow test is running and to keep track of number of test samples taken.
4. Counter will increment each time a test sample is taken.

PCM monitors EGR valve pintle position input to ensure that valve responds properly to commands from PCM. The EGR (linear) valve is controlled by using an ignition positive driver and ground circuit within PCM. Driver has the ability to detect an electrical malfunction in the ignition voltage or ground circuit, then signal PCM to set DTC P0403.

PCM will run diagnostic for this DTC under the following conditions

1. Engine is cranking or running.
2. System voltage is 9-18 volts.

DTC will set when PCM detects an electrical malfunction in EGR valve control circuit for more than 20 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, observe EGR position sensor parameter, and command EGR from 0 percent to 100 percent. If EGR position sensor parameter remains close to desired EGR position parameter at all commanded positions, go to next step. If EGR position sensor parameter does not remain close to desired EGR position parameter at all commanded positions, go to step 4.
3. Using scan tool, observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Operate vehicle within conditions required to set DTC or as close to the FREEZE FRAME/FAILURE RECORDS data that you observe. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed this ignition cycle, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect EGR valve harness connector. Turn ignition on. Connect a test light between ground and EGR solenoid high control circuit at EGR valve harness connector terminal "E". See «EGR VALVE CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table. (Scheme 23) Using scan tool, command EGR between zero percent and 10 percent. If test light turns on and off with each command, go to next step. If test light does not turn on and off with each command, go to step 6.
5. Connect test light between EGR solenoid high control circuit at EGR valve harness connector terminal "E" and EGR solenoid low control circuit at EGR valve harness connector terminal "A". Using scan tool, command EGR between zero percent and 10 percent. 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 step 9.
6. If test light remains illuminated with each command, go to step 8. If test light does not remain illuminated with each command, go to next step.
7. Check for open or short to ground in EGR solenoid high control circuit between EGR valve harness connector terminal "E" and PCM harness connector C2 terminal No. 4. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 14. If circuit is okay, go to step 11.
8. Check short to voltage in EGR solenoid high control circuit between EGR valve harness connector terminal "E" and PCM harness connector C2 terminal No. 4. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 14. If circuit is okay, go to step 11.
9. Check for open or high resistance in EGR solenoid low control circuit between EGR valve harness connector terminal "A" and PCM harness connector C1 terminal No. 32. Repair circuit as necessary, then go to step 14. If circuit is okay, go to step 11.
10. Inspect EGR valve harness connector for poor connections. Repair connector as necessary, then go to step 14. If connector is okay, go to step 12.
11. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step 14. If connector is okay, go to step 13.
12. Replace EGR valve. After repairs, go to step 14.
13. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
14. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
15. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

EGR VALVE CIRCUIT IDENTIFICATION

Scheme 23

PCM monitors EGR valve pintle position input to ensure that EGR valve responds properly to commands from PCM. PCM compares EGR position sensor with desired EGR position when valve is commanded open. If difference between EGR position sensor parameter and desired EGR position is more than 15 percent, this DTC P0404 will set.

PCM will run diagnostic for this DTC when system voltage is more than 11 volts and EGR valve is enabled. DTC will set when difference between EGR position sensor parameter and desired EGR position is more than 15 percent for longer than 20 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC P0403 or P0405 is present. If any of these DTCs are present, diagnose affected DTC first. See «DTC P0403: EGR SOLENOID CONTROL CIRCUIT»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) or «DTC P0405: EGR POSITION SENSOR CIRCUIT - LOW VOLTAGE»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). If DTC P0403 or P0405 is not present, command EGR valve from 0-100 percent with scan tool. Compare desired EGR position to actual EGR position. If desired and actual EGR positions remain within 15 percent of each other at all commanded positions, go to next step. If desired and actual EGR position is not within range, go to step 4.
3. Using scan tool, observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off and wait 30 seconds. Operate vehicle under conditions required to set DTC or as close to FREEZE FRAME/FAILURE RECORDS data as possible. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed in this ignition cycle, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
4. Turn ignition off. Disconnect EGR valve harness connector. Turn ignition on. Using scan tool, read EGR position sensor parameter. If scan tool displays zero percent, go to next step. If scan tool does not display zero percent, go to step 8.
5. Measure voltage between low reference circuit (Black wire) at EGR valve harness connector terminal "B" and 5-volt reference circuit at EGR valve harness connector terminal "D". (Scheme 23) See «EGR VALVE CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table under DTC P0403: EGR SOLENOID CONTROL CIRCUIT. If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step 7.
6. Connect a 3-amp fused jumper wire between 5-volt reference circuit at EGR valve harness connector terminal "D" and EGR pintle position signal circuit at EGR valve harness connector terminal "C". Using scan tool, observe actual EGR position. If actual EGR position is 100 percent, go to step 12. If actual EGR position is not 100 percent, go to step 10.
7. Measure voltage between a good ground and 5-volt reference circuit at EGR valve harness connector terminal "D". If voltage is about 5 volts, go to step 9. If voltage is not about 5 volts, go to step 11.
8. Check for short to voltage in EGR pintle position signal circuit between EGR valve harness connector terminal "C" and PCM harness connector C2 terminal No. 28. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 16. If circuit is okay, go to step 13.
9. Check for open or high resistance in low reference circuit (Black wire) between EGR valve harness connector terminal "B" and PCM harness connector C1 terminal No. 31. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 16. If circuit is okay, go to step 13.
10. Check for high resistance or short to ground (with high resistance) in EGR pintle position signal circuit between EGR valve harness connector terminal "C" and PCM harness connector C2 terminal No. 28. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 16. If circuit is okay, go to step 13.
11. Check for open, short to ground or short to voltage in 5-volt reference circuit between EGR valve harness connector terminal "D" and PCM harness connector C2 terminal No. 30. Repair circuit as necessary, then go to step 16. If circuit is okay, go to step 13.
12. Inspect EGR valve harness connector for poor connections. Repair connector as necessary, then go to step 16. If connector is okay, go to step 14.
13. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step 16. If connector is okay, go to step 15.
14. Replace EGR valve. After repairs, go to step 16.
15. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
16. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
17. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Check for excessive deposits on EGR valve pintle or seat. Check for poor connection at PCM or EGR valve harness connectors. If DTC is determined to be intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

PCM monitors EGR valve pintle position input to ensure that EGR valve responds properly to commands from PCM and to detect a fault if EGR pintle position sensor circuit is open or shorted. If PCM detects an excessively low EGR position sensor signal voltage, DTC P0405 will set.

PCM will run diagnostic for this DTC when system voltage is more than 11 volts. DTC will set when EGR pintle position feedback voltage is less than .35 volt for longer than 20 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, observe EGR position sensor voltage parameter. If scan tool displays less than.35 volt, go to step 4. If scan tool does not display less than.35 volt, go to next step.
3. Using scan tool, review FAILURE RECORDS data. Turn ignition off and wait 30 seconds. Operate vehicle under conditions required to set DTC or as close to FAILURE RECORDS data as possible. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed in this ignition cycle, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES -CARS article.
4. Turn ignition off. Disconnect EGR valve harness connector. Connect a fused jumper wire between 5-volt reference circuit at EGR valve harness connector terminal "D" and EGR valve position sensor circuit at EGR valve harness connector terminal "C". See «EGR VALVE CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table under DTC P0403: EGR SOLENOID CONTROL CIRCUIT. (Scheme 23) Turn ignition on. Using scan tool, observe EGR valve position sensor parameter. If scan tool displays about 100 percent, go to step 10. If scan tool does not display about 100 percent, go to next step.
5. Remove jumper wire. Measure voltage between 5-volt reference circuit at EGR valve harness connector terminal "D" and low reference circuit (Black wire) at EGR valve harness connector terminal "B". If voltage is about 5 volts, go to step 9. If voltage is not about 5 volts, go to next step.
6. Check for open or high resistance in 5-volt reference circuit between EGR valve harness connector terminal "D" and PCM harness connector C2 terminal No. 30. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 15. If circuit is okay, go to next step.
7. Check for short to ground in all 5-volt reference circuits. See WIRING DIAGRAMS article. If a problem is found, repair as necessary, then go to step 15. If all circuits are okay, go to next step.
8. Measure voltage between 5-volt reference circuit at EGR valve harness connector terminal "D" and low reference circuit (Black wire) at EGR valve harness connector terminal "B". While observing voltage, individually disconnect each sensor that uses a 5-volt reference signal. A change in voltage indicates faulty component. Replace faulty component as necessary, then go to step 15. If voltage does not change, go to step 11.
9. Check for open, high resistance or short to ground in EGR valve position signal circuit between EGR valve harness connector terminal "C" and PCM harness connector C2 terminal No. 28. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 15. If circuit is okay, go to step 11.
10. Check for short between EGR valve position signal circuit at EGR valve harness connector terminal "C" and EGR solenoid high control circuit at EGR valve harness connector terminal "E". Repair circuit as necessary, then go to step 15. If circuit is okay, go to step 12.
11. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step 15. If connector is okay, go to step 14.
12. Inspect EGR valve harness connector for poor connections. Repair connector as necessary, then go to step 15. If connector is okay, go to next step.
13. Replace EGR valve. After replacing EGR valve, go to step 15.
14. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
15. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
16. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

To control emissions HC, CO and NOx, a three-way catalytic converter is used. The catalyst within the converter promotes a chemical reaction which oxidizes HC and CO present in exhaust gas, converting them into harmless water vapor and carbon dioxide. The catalyst also reduces NOx, converting it to nitrogen. The converter also has the ability to store excess oxygen and release the stored oxygen to promote these reactions. This oxygen storage capacity is a measurement of the catalysts ability to control emissions.

PCM monitors this process using a Heated Oxygen Sensor (HO2S) located in exhaust stream past the three-way converter. When catalyst is functioning properly, HO2S 2 is slow to respond to a large change in HO2S 1 signal. When HO2S 2 responds quickly to a large change in HO2S 1 signal, oxygen storage capacity and efficiency of catalyst is considered to be bad and MIL will be illuminated if subsequent tests also indicate a failure.

1. Meet conditions for engine warm-up. Using scan tool catalyst data list, verify the following: DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0131, P0134, P0135, P0137, P0138, P0140, P0141, P0171, P0172, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0336, P0341, P0401, P0403, P0404, P0405, P0440, P0442, P0443, P0446, P0449, P0502, P0503, P0506, P0507, P1133, P1134, P1336, P1351, P1352, P1361, P1362, P1374, P1404 or P1441 are not set. Engine has been running for more than 10 minutes. Engine coolant temperature is 158-255°F (70-124°C). Barometric Pressure (BARO) is more than 75 kPa. Vehicle is in closed loop. Intake air temperature is -4 to 212°F (-20 to 100°C). Battery voltage is more than 10.7 volts.
2. Warm catalyst as follows: Open hood. Place transmission in Park or Neutral. Set parking brake. Press and hold service brakes. Each time engine is started, diagnostic can run up to 18 times. After the 10 minute run time, and before the diagnostic runs the first time, engine must run an additional 5 minutes at 1500-2500 RPM. For any additional tests on the same ignition cycle, engine must be 1500-2500 RPM for one minute. In order to activate diagnostic, return to idle and place vehicle in Drive (A/T), or depress clutch pedal (M/T).
3. Test catalyst as follows: Verify that transaxle is in Drive (A/T) or is in Neutral with clutch pedal depressed (MT). Within 60 seconds, air/fuel ratio will go lean for up to 7 seconds, and may then may go rich for up to 7 seconds. Use scan tool in order to determine if DTC P0420 has passed or failed this ignition cycle.

DTC will set when PCM determines that the catalyst's oxygen storage capacity is less than acceptable.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Check for any other DTCs. If other DTCs are set, diagnose those DTCs first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If no other DTCs are set, go to next step. NOTE: If more than 6 tests have been attempted and DTC has not passed or failed this ignition cycle, test may be aborting. See «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) .
3. Using scan tool, clear DTCs. Ensure A/C is turned off. Start and warm engine to normal operating temperature. Open hood. Operate vehicle within conditions for setting this DTC. Using scan tool, verify if DTC ran and passed in this ignition cycle. If scan tool indicates that this test ran and passed, system is okay. If scan tool does not indicate that this test ran and passed, go to next step.
4. Check 3-way catalytic converter for damage, severe discoloration due to heat, holes or internal rattle. Verify if converter is proper original equipment part or replacement. If a problem is found, go to step 9 . If no problem is found, go to next step.
5. Check exhaust system for leaks. If leak is found, go to step 7 . If no leak is found, go to next step.
6. Check for damaged oxygen sensor or sensor wiring. If a problem is found, go to step 8 . If no problem is found, go to step 9 .
7. Repair exhaust system as necessary. After repairs, go to step 10 .
8. Repair oxygen sensor or sensor wiring. After repairs, go to step 10 .
9. Replace catalytic converter. After replacing converter, go to next step.
10. Using scan tool, clear DTCs. Ensure A/C is turned off. Start and warm engine to normal operating temperature. Open hood. Operate vehicle within conditions for setting this DTC. Using scan tool, verify if DTC ran and passed in this ignition cycle. 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 4 .
11. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs, system is okay.

PCM will not enable catalyst test until following conditions are met

1. Engine speed is within 200 RPM of desired idle speed.
2. Throttle position is 1.5 percent or less.
3. Short term fuel trim is between -20 and +20 percent.

Catalyst test will abort if vehicle falls outside the conditions listed above while test is running. Catalyst test may abort due to a change in engine load. If this condition occurs, use scan tool to force cooling fans on and return to Step 3 in DIAGNOSTIC PROCEDURE.

PCM tests EVAP system for a large leak. PCM monitors Fuel Tank Pressure (FTP) sensor signal to determine EVAP system vacuum level. When conditions are met, PCM commands EVAP canister purge valve open and EVAP vent valve closed. This allows engine vacuum to enter EVAP system. At a calibrated time, or vacuum level, PCM commands EVAP canister purge valve closed, sealing the system, and monitors FTP sensor input in order to determine EVAP system vacuum level. If system is unable to achieve the calibrated vacuum level, or vacuum level decreases too rapidly, DTC P0440 will set.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0443, P0449, P0452, P0453, P1106, P1107, P1112, P1114, P1115, P1121 or P1122 are not set.
2. System voltage is 10-18 volts.
3. Barometric pressure is more than 75 kPa.
4. Fuel level is 15-85 percent.
5. Engine Coolant Temperature (ECT) and Intake Air Temperature (IAT) is 39-86°F (4-30°C).
6. Start-up ECT and IAT are within 16°F of each other.
7. Vehicle speed is less than 75 MPH.

DTC will set 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»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Check if DTC P0443 or P0449 is also set. If DTC P0443 or P0449 is set, diagnose affected DTC first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If DTC P0443 or P0449 is 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 filler cap. Damaged EVAP canister purge valve. Disconnected, improperly routed, kinked or damaged EVAP pipes and hoses. Damaged EVAP canister vent valve or EVAP canister. For component locations, see VACUUM DIAGRAMS - CARS article. If a problem is found, repair as necessary, then go to step 18 . If no problems were found, go to next step.
4. Install Fuel Tank Cap Adaptor (J 41415-40). Connect EVAP Pressure and Purge Station (J 41413) and fuel filler cap to fuel tank cap adapter. Turn ignition on. Using scan tool, seal EVAP system. Using pressure and purge station, pressurize system to 5 in. H20. Rotate rotary switch on pressure and purge station to OFF/HOLD position. Monitor pressure gauge for one minute. If 5 in. H20 is obtained, go to next step. If 5 in. H20 is not obtained, go to step 7 .
5. If value on pressure and purge station is close to FTP sensor value on scan tool, go to next step. If value on pressure and purge station is not close to FTP sensor value on scan tool, go to step 11 .
6. While monitoring gauge on pressure and purge station, disconnect purge pipe from EVAP purge valve. If EVAP system pressure decreases, go to step 8 . If EVAP system pressure does not decrease, go to step 9 .
7. With pressure still applied to EVAP system, use Ultrasonic Leak Detector (J 41416) to check for leaks in the following areas: EVAP system hoses/pipes. Fuel filler hose/pipe and fuel cap. EVAP canister. EVAP canister purge valve. EVAP canister vent valve. Fuel sender assembly and/or seal. FTP sensor seal. Fill limiter vent valve. Pressure relief valve, rollover valves and fuel tank. If a leak is found, repair as necessary, then go to step 18 . If no leaks were found, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) .
8. Connect a vacuum gauge to EVAP canister purge valve purge pipe port. Start engine and let it idle. Using scan tool, command EVAP canister purge valve to 50 percent. If vacuum gauge shows more than 10 in. Hg, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . If vacuum gauge does not show more than 10 in. Hg, go to step 12 .
9. While monitoring gauge on pressure and purge station, disconnect purge pipe from EVAP canister. If pressure decreases, go to step 14 . If pressure does not decrease, go to next step.
10. While monitoring gauge on pressure and purge station, disconnect EVAP vapor line from EVAP canister. If EVAP system pressure decreases, go to step 17 . If EVAP system pressure does not decrease, go to step 13 .
11. Using scan tool, monitor FTP sensor. If scan tool displays more than 4.3 volts, see «DTC P0453: FUEL TANK PRESSURE SENSOR CIRCUIT - HIGH VOLTAGE»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . If scan tool does not display more than 4.3 volts, go to step 15 .
12. Inspect vacuum source to EVAP canister purge valve for blockage or leak. If a problem is found, repair as necessary, then go to step 18 . If no problem is found, go to step 16 .
13. Repair the pinched or obstructed EVAP vapor pipe. After repairs, go to step 18 .
14. Repair restriction in EVAP purge pipe. After repairs, go to step 18 .
15. Replace FTP sensor. After repairs, go to step 18 .
16. Replace the EVAP canister purge valve. After repairs, go to step 18 .
17. Replace EVAP canister. After repairs, go to step 18 .
18. Turn ignition on. Using scan tool, command EVAP canister vent valve on. Using pressure and purge station, pressurize system to 5 in. H20. Place control knob on pressure and purge station to OFF/HOLD position. Monitor gauge on pressure and purge station for 5 minutes. If pressure remains constant, go to next step. If pressure does not remain constant, go to step 7 .
19. While monitoring gauge on pressure and purge station, command EVAP canister purge valve to 50 percent with scan tool. If EVAP system pressure decreases, go to next step. If EVAP system pressure does not decrease, go to step 9 .
20. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs that have not been diagnosed, system is okay.

Pressurize the EVAP system with pressure and purge station to aid in locating intermittent leaks. Move all EVAP components while testing with ultrasonic leak detector. A temporary blockage in EVAP canister purge valve, purge pipe or EVAP canister could cause an intermittent condition. 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.

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

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0440, P0443, P0449, P0452, P0453, P1106, P1107, P1112, P1114, P1115, P1121 or P1122 are not set.
2. Ignition voltage is 10-18 volts.
3. Barometric pressure is more than 75 kPa.
4. Fuel level is 15-80 percent.
5. Engine Coolant Temperature (ECT) and Intake Air Temperature (IAT) are 39-86°F (4-30°C).
6. Start-up ECT and IAT are within 16°F of each other.
7. Vehicle speed is less than 75 MPH.

DTC will set 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»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. If DTC P0443, P0449, P0452 or P0453 is also set, diagnose those codes first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If DTC P0443, P0449, P0452 or P0453 is 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 filler cap. Damaged EVAP canister purge valve. Disconnected, improperly routed, kinked or damaged EVAP pipes and hoses. Damaged EVAP canister vent valve or EVAP canister. For component locations, see VACUUM DIAGRAMS - CARS article. If a problem is found, repair as necessary, then go to step 6 . If no problems were found, go to next step.
4. Install Fuel Tank Cap Adapter (J 41415-40). Connect EVAP Pressure and Purge Station (J 41413) and fuel filler cap to fuel tank cap adapter. Turn ignition on. Using scan tool, seal EVAP system. Using pressure and purge station, continuously pressurize system to 15 in. H20. Using Ultrasonic Leak Detector (J 41416), check for leaks in the following areas: EVAP system hoses/pipes. Fuel filler hose/pipe and fuel cap. EVAP canister. EVAP canister purge valve. EVAP canister vent valve. Fuel sender assembly and/or seal. FTP sensor seal. Fill limiter vent valve. Pressure relief valve, rollover valves and fuel tank. If a leak is found, repair as necessary, then go to next step. If no leaks were found, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) .
5. Remove fuel filler cap for 30 seconds to relieve fuel tank pressure. Reinstall fuel filler cap. Turn ignition on. Using scan tool, command EVAP canister vent valve on. Using pressure and purge station, pressurize system to 5 in. H20. Place control knob on pressure and purge station to OFF/HOLD position. Monitor gauge on pressure and purge station for 5 minutes. If pressure remains constant, go to next step. If pressure does not remain constant, go to step 4 .
6. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs that have not been diagnosed, system is okay.

EVAP system test runs when engine is first started and meets conditions under CODE ENABLE CRITERIA. To aid in locating intermittent leaks, use pressure and purge station to pressurize EVAP system. Move all EVAP components while testing with ultrasonic leak detector.

Ignition voltage is supplied directly to EVAP purge valve. EVAP purge valve is Pulse Width Modulated (PWM). PCM controls EVAP purge valve on time by grounding control circuit via an internal switch called a driver. Scan tool displays amount of on time as a percentage. PCM monitors status of the driver. If PCM detects an incorrect voltage for the commanded state of the driver, DTC P0443 sets.

PCM will run diagnostic for this DTC when engine speed is more than 400 RPM and system voltage is 6-18 volts. DTC will set when PCM detects that commanded state of driver and actual state of control circuit do not match for 5 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, command EVAP canister purge valve to 50 percent, then to zero percent. If EVAP canister purge valve clicks when commanded to 50 percent, go to next step. If EVAP canister purge valve does not click when commanded to 50 percent, go to step 4.
3. Using scan tool, review FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off and wait 30 seconds. Start engine. Operate vehicle under conditions for setting DTC or as close to FREEZE FRAME and/or FAILURE RECORDS data as possible. If scan tool indicates that this DTC failed this ignition, go to next step. If scan tool does not indicate that this DTC failed this ignition, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect EVAP canister purge valve harness connector. For component locations, see VACUUM DIAGRAMS - CARS article. Turn ignition on. Connect a test light between ground and ignition voltage circuit (Brown wire on Alero, Grand Am & Malibu; Pink wire on all other models) at EVAP canister purge solenoid harness connector terminal "A". If test light illuminates, go to next step. If test light does not illuminate, go to step 11.
5. Connect test light between ignition voltage circuit (Brown wire on Alero, Grand Am & Malibu; Pink wire on all other models) at EVAP canister purge valve harness connector terminal "A" and control circuit (Dark Green/White wire) at EVAP canister purge valve harness connector terminal "B". Using scan tool, command EVAP canister purge valve to 50 percent, then to zero percent. If test light turns on or flashes when EVAP canister purge valve is commanded to 50 percent, go to step 9. If test light does not turn on or flash when EVAP canister purge valve is commanded to 50 percent, go to next step.
6. If test light remains illuminated with each command, go to step 8. If test light does not remain illuminated with each command, go to next step.
7. Check for open or short to voltage in control circuit (Dark Green/White wire) between EVAP canister purge valve harness connector terminal "B" and PCM harness connector C1 terminal No. 76. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 14. If circuit is okay, go to step 10.
8. Check for short to ground in control circuit (Dark Green/White wire) between EVAP canister purge valve harness connector terminal "B" and PCM harness connector C1 terminal No. 76. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 14. If circuit is okay, go to step 13.
9. Inspect EVAP canister purge valve harness connector for poor connections. Repair connector as necessary, then go to step 14. If connector is okay, go to step 12.
10. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step 14. If connector is okay, go to step 13.
11. Repair ignition voltage circuit between EVAP canister purge valve and underhood fuse block. See WIRING DIAGRAMS article. After repairs, go to step 14.
12. Replace EVAP canister purge valve. After repairs, go to step 14.
13. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
14. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
15. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

This DTC tests EVAP system for a restricted or blocked EVAP vent path. PCM commands EVAP canister purge valve on and EVAP canister vent valve on. This allows a vacuum to be applied to EVAP system. Once a calibrated vacuum level has been reached, PCM commands EVAP canister purge valve off and EVAP canister vent valve off. PCM monitors Fuel Tank Pressure (FTP) sensor for a decrease in vacuum. If vacuum does not decrease to near zero inches H2O in a calibrated time, this DTC P0446 will set.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0440, P0442, P0443, P0449, P0452, P0453, P1106, P1107, P1112, P1114, P1115, P1121 or P1122 are not set.
2. Ignition voltage is 10-18 volts.
3. Barometric pressure is more than 75 kPa.
4. Fuel level is 15-85 percent.
5. Engine Coolant Temperature (ECT) and Intake Air Temperature (IAT) are between 39-86°F (4-30°C).
6. Start-up ECT and IAT are 16°F of each other.
7. Vehicle speed is less than 75 MPH.

DTC will set when FTP is less than 10 in. H2O for at least 30 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. If DTC P0443, P0449, or P0453 are set, diagnose affected DTC first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If DTC P0443, P0449, or P0453 are not set, go to next step.
3. Inspect EVAP vent valve for damage. Check for pinched EVAP vent hose. For component locations, see VACUUM DIAGRAMS - CARS article. If a problem is found, repair as necessary, then go to step 14 . If no problems were found, go to next step.
4. Disconnect purge line from EVAP canister purge valve. Turn ignition on. Using scan tool, observe Fuel Tank Pressure (FTP) parameter. If scan tool displays zero in. H2O, go to next step. If scan tool does not display zero in. H2O, go to step 8 .
5. Turn ignition off. Reconnect all previously disconnected components. Install Fuel Fill Cap Adapter (J 41415). Connect EVAP Pressure and Purge Station (J 41413) and fuel fill cap to fuel fill cap adapter. Turn ignition on. Using scan tool, command EVAP canister vent valve on. Using EVAP pressure and purge station, pressurize EVAP system to 5 in. H2O. Turn rotary switch on pressure and purge station to OFF/HOLD position. Using scan tool, command EVAP canister vent valve off. If scan tool indicates that FTP is about zero in. H2O, go to step 10 . If scan tool does not indicate that FTP is about zero in. H2O, go to step 7 .
6. Disconnect EVAP canister vent hose from EVAP canister vent valve. If scan tool indicates that FTP is -0.5 in. H2O to +0.5 in. H2O, go to step 10 . If scan tool does not indicate that FTP is -0.5 in. H2O to +0.5 in. H2O, go to next step.
7. Disconnect EVAP vent pipe from EVAP canister. If scan tool indicates that FTP is about zero in. H2O, go to step 13 . If scan tool does not indicate that FTP is about zero in. H2O, go to step 11 .
8. Using scan tool, observe FTP sensor voltage. If scan tool displays more than 4.3 volts, see «DTC P0453: FUEL TANK PRESSURE SENSOR CIRCUIT - HIGH VOLTAGE»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . If scan tool does not display more than 4.3 volts, go to next step.
9. Inspect FTP sensor harness connector for poor connections. On Alero, Grand Am and Malibu, fuel tank must be removed for access to FTP sensor harness connector. On all other models, remove fuel sender access panel located under trunk liner. On all models, repair connector as necessary, then go to step 14 . If connector is okay, go to step 12 .
10. Replace EVAP canister vent valve. After repairs, go to step 14 .
11. Replace EVAP canister. After repairs, go to step 14 .
12. Replace FTP sensor. After repairs, go to step 14 .
13. Repair blockage in EVAP vent hose. After repairs, go to next step.
14. Turn ignition on. Using scan tool, command EVAP canister vent valve on. Using EVAP pressure and purge station, pressurize EVAP system to 5 in. H2O. Turn rotary switch on pressure and purge station to OFF/HOLD position. Monitor pressure gauge on EVAP pressure and purge station. Using scan tool, command EVAP canister vent valve off. If pressure decreases, go to next step. If pressure does not decrease, go to step 3 .
15. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs, system is okay.

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.

Ignition voltage is supplied directly to EVAP canister vent valve. PCM controls EVAP canister vent valve by grounding control circuit via an internal switch called a driver. PCM monitors the status of the driver. If PCM detects an incorrect voltage for the commanded state of the driver, DTC P0449 sets.

PCM will run diagnostic for this DTC when system voltage is 6-18 volts and engine speed is more than 400 RPM. DTC will set when PCM detects that the commanded state of the driver and actual state of the control circuit do not match. Conditions must be present for at least 5 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, command EVAP canister vent valve on and off. If EVAP canister vent valve clicks when commanded on and off, go to next step. If EVAP canister vent valve does not click when commanded on and off, go to step 4.
3. Using scan tool, review FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off and wait 30 seconds. Start engine. Operate vehicle under conditions for setting DTC or as close to FREEZE FRAME and/or FAILURE RECORDS data as possible. If scan tool indicates that this DTC failed this ignition, go to next step. If scan tool does not indicate that this DTC failed this ignition, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect EVAP canister vent valve harness connector. Turn ignition on. Connect a test light between ground and ignition voltage circuit (Brown wire on Alero, Grand Am and Malibu; Pink wire on all other models) at EVAP canister vent valve harness connector terminal "A". If test light illuminates, go to next step. If test light does not illuminate, go to step 11.
5. Connect test light between ignition voltage circuit (Brown wire on Alero, Grand Am and Malibu; Pink wire on all other models) at EVAP canister vent valve harness connector terminal "A" and control circuit (White wire) at EVAP canister vent valve harness connector terminal "B". Using scan tool, command EVAP canister vent valve 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.
6. If test light remains illuminated with each command, go to step 8. If test light does not remain illuminated with each command, go to next step.
7. Check for open or short to voltage in control circuit (White wire) between EVAP canister vent valve harness connector terminal "B" and PCM harness connector C2 terminal No. 2. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 14. If circuit is okay, go to step 10.
8. Check for short to ground in control circuit (White wire) between EVAP canister vent valve harness connector terminal "B" and PCM harness connector C2 terminal No. 2. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 14. If circuit is okay, go to step 10.
9. Inspect EVAP canister vent valve harness connector for poor connections. Repair connector as necessary, then go to step 14. If connector is okay, go to step 12.
10. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step 14. If connector is okay, go to step 13.
11. Repair ignition voltage circuit between EVAP canister vent valve and underhood junction block (on Alero, Century, Grand Am and Malibu) or instrument panel junction block (on Grand Prix, Impala and Monte Carlo). See WIRING DIAGRAMS article. After repairs, go to step 14.
12. Replace EVAP canister vent valve. After repairs, go to step 14.
13. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
14. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
15. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

PCM monitors Fuel Tank Pressure (FTP) sensor signal in order to detect vacuum decay and excess vacuum during the enhanced EVAP diagnostic. PCM supplies a 5-volt reference and ground to FTP 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 goes below a predetermined value, DTC P0452 will set.

PCM will run diagnostic for this DTC when engine is running. DTC will set when FTP sensor voltage is less than .1 volt for more than 5 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Allow engine to idle for one minute. Using scan tool, read DTCs. If DTC P1635 or P1639 failed this ignition cycle, diagnose affected DTC first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If DTC P1635 or P1639 did not fail this ignition cycle, go to next step.
3. Using scan tool, observe FTP sensor voltage. If scan tool displays less than.1 volt, go to step 5. If scan tool does not display less than.1 volt, go to next step.
4. Using scan tool, observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within conditions for setting DTC or as close to FREEZE FRAME/FAILURE RECORDS data as possible. If DTC fails this ignition cycle, go to next step. If DTC does not fail this ignition cycle, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
5. Turn ignition off. Disconnect FTP sensor harness connector. On Alero, Grand Am and Malibu, fuel tank must be removed for access to FTP sensor harness connector. On all other models, remove fuel sender access panel located under trunk liner. On all models, connect a 3-amp fused jumper wire between 5-volt reference circuit (Gray/Black wire on Century; Gray wire on all other models) at terminal "C" and signal circuit (Dark Green wire) at terminal "B" at FTP sensor harness connector. Turn ignition on. Using scan tool, observe FTP sensor voltage. If scan tool displays about 5 volts, go to step 8. If scan tool does not display about 5 volts, go to next step.
6. On Century, check for open, high resistance or short to ground in 5-volt reference circuit between FTP sensor harness connector terminal "C" (Gray/Black wire) and PCM harness connector C2 terminal No. 34 (Gray wire). On all other models, check for open, high resistance or short to ground in 5-volt reference circuit (Gray wire) between FTP sensor harness connector terminal "C" and PCM harness connector C2 terminal No. 32. On all models, see «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 12. If circuit is okay, go to next step.
7. Check for open, high resistance or short to ground in signal circuit (Dark Green wire) between FTP sensor harness connector terminal "B" and PCM harness connector C2 terminal No. 55. Repair circuit as necessary, then go to step 12. If circuit is okay, go to step 9.
8. Inspect FTP sensor harness connector for poor connections. Repair connector as necessary, then go to step 12. If connector is okay, go to step 10.
9. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step 12. If connector is okay, go to step 11.
10. Replace FTP sensor. After repairs, go to step 12.
11. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
12. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
13. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

PCM monitors Fuel Tank Pressure (FTP) sensor signal in order to detect vacuum decay and excess vacuum during the enhanced EVAP diagnostic. PCM supplies a 5-volt reference and ground to FTP 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 goes below a predetermined value, DTC P0452 will set.

PCM will run diagnostic for this DTC when engine is running. DTC will set when FTP sensor voltage is more than 4.9 volts for more than 5 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Allow engine to idle for one minute. Using scan tool, read DTCs. If DTC P1635 or P1639 failed this ignition cycle, diagnose affected DTC first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If DTC P1635 or P1639 did not fail this ignition cycle, go to next step.
3. Using scan tool, observe FTP sensor voltage. If scan tool displays more than 4.3 volts, go to step 5. If scan tool does not display more than 4.3 volt, go to next step.
4. Using scan tool, observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within conditions for setting DTC or as close to FREEZE FRAME/FAILURE RECORDS data as possible. If DTC fails this ignition cycle, go to next step. If DTC does not fail this ignition cycle, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
5. Turn ignition off. Disconnect FTP sensor harness connector. On Alero, Grand Am and Malibu, fuel tank must be removed for access to FTP sensor harness connector. On all other models, remove fuel sender access panel located under trunk liner. On all models, turn ignition on. Using scan tool, observe FTP sensor voltage. If scan tool displays more than 4.3 volts, go to next step. If scan tool does not display more than 4.3 volts, go to step 7.
6. Check signal circuit (Dark Green wire) between FTP sensor harness connector terminal "B" and PCM harness connector C2 terminal No. 55 for short to voltage or short to 5-volt reference circuit. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 13. If circuit is okay, go to step 12.
7. Connect a test light between battery positive and low reference circuit (Black wire on Grand Prix; Orange/Black wire on all other models) at FTP sensor harness connector terminal "A". If test light illuminates, go to step 9. If test light does not illuminate, go to next step.
8. Check for open in low reference circuit between FTP sensor harness connector terminal "A" (Black wire on Grand Prix; Orange/Black wire on all other models) and PCM harness connector C2 terminal No. 35 (Black wire). See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 13. If circuit is okay, go to step 10.
9. Inspect FTP sensor harness connector for poor connections. Repair connector as necessary, then go to step 13. If connector is okay, go to step 11.
10. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step 13. If connector is okay, go to step 12.
11. Replace FTP sensor. After repairs, go to step 13.
12. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
13. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
14. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

PCM uses an Output Driver Module (ODM) to control ground (control) circuit to cooling fan relay. ODM is also used by PCM to diagnose the output of this circuit.

PCM will run diagnostic for this DTC when ignition is on. DTC will set when an improper voltage level has been detected on relay control circuit for 30 seconds or more.

1. Perform engine cooling diagnostic system check. See «ENGINE COOLING DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__engine-cooling-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing engine cooling diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, command low speed cooling fans on and off. Listen for cooling fan relay No. 1 operation. Cooling fan relay No. 1 is located in underhood fuse block. If cooling fan relay No. 1 turns on and off with each command, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). If relay does not turn on and off with each command, go to next step.
3. Turn ignition off. Remove cooling fan relay No. 1. Turn ignition on. Connect a test light between ground and relay coil battery feed circuit. If test light illuminates, go to next step. If test light does not illuminate, go to step 8.
4. Connect test light between relay coil battery feed circuit and relay control circuit. Using scan tool, command low speed cooling fans 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 illuminated for each command, go to step 7. If test light does not remain illuminated for each command, go to next step.
6. Check for open or short to voltage in control circuit (Dark Green wire) between cooling fan relay No. 1 and PCM harness connector C1 terminal No. 6. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 14. If circuit is okay, go to step 9.
7. Check for short to ground in control circuit (Dark Green wire) between cooling fan relay No. 1 and PCM harness connector C1 terminal No. 6. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 14. If circuit is okay, go to step 9.
8. Check for open or short to ground in relay coil battery feed circuit. Repair circuit as necessary, then go to step 14. If circuit is okay, go to step 11.
9. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step 14. If connector is okay, go to step 13.
10. Check for poor connections at cooling fan relay No. 1. If a problem is found, repair as necessary, then go to step 14. If a problem is not found, go to step 12.
11. Repair short to ground in cooling fan motor supply voltage circuit. See WIRING DIAGRAMS article. After repairs, go to step 14.
12. Replace cooling fan relay No. 1. After repairs, go to step 14.
13. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
14. Using scan tool, clear DTCs. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, system is okay. If scan tool does not indicate that this test ran and passed, go to step 2.

Intermittent can be caused by poor connection, rubbed-through wire insulation, or a wire broken inside the insulation. Check connectors for backed-out terminals, improper mating, broken lock, damaged terminal or poor terminal to wire connection.

Using FREEZE FRAME and/or FAILURE RECORDS data mode may aid in locating an intermittent condition. If DTC cannot be duplicated, information included in FREEZE FRAME and/or FAILURE RECORDS data can be useful in determining how many miles since DTC set. FAIL COUNTER and PASS COUNTER can also be used to determine how many ignition cycles diagnostic reported a pass or a fail condition. To isolate when DTC failed, operate vehicle within same freeze frame conditions (RPM, load, vehicle speed, temperature, etc.).

DTC P0481: COOLING FAN RELAY NO. 2 CONTROL CIRCUIT

Note. Cooling fan relay No. 2 refers to relay that controls supply voltage to left cooling fan motor (on Impala and Monte Carlo) or right cooling fan motor (on all other models).

PCM uses an Output Driver Module (ODM) to control ground (control) circuit to cooling fan relay. ODM is also used by PCM to diagnose the output of this circuit.

PCM will run diagnostic for this DTC when ignition is on. DTC will set when an improper voltage level has been detected on relay control circuit for 30 seconds or more.

Diagnostic Procedure (Alero, Grand Am & Malibu)

1. Perform engine cooling diagnostic system check. See «ENGINE COOLING DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__engine-cooling-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing engine cooling diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, command high speed cooling fans on and off. Listen for cooling fan relay operation. Cooling fan relays are located in underhood fuse block. Cooling fan mode relay and cooling fan relay No. 2 should operate. If relays turn on and off with each command, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). If operation is not as specified, go to next step.
3. Turn ignition off. Remove cooling fan relay No. 2. Turn ignition on. Connect a test light between ground and coil feed circuit. If test light illuminates, go to next step. If test light does not illuminate, go to step 8.
4. Connect test light between control circuit and battery feed circuit of cooling fan relay No. 2. Using scan tool, command high speed cooling fans on and off. If test light turns on and off with each command, go to step 9. If test light does not respond as specified, go to next step.
5. If test light remains illuminated with each command, go to step 7. If test light does not remain illuminated with each command, go to next step.
6. Check for open or short to voltage in high speed cooling fan relay control circuit between cooling fan mode relay, cooling fan relay No. 2, and PCM harness connector C1 terminal No. 5 (Dark Blue wire). (Scheme 5) See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Repair circuit as necessary, then go to step 12. If circuit is okay, go to step 9.
7. Check for short to ground in high speed cooling fan relay control circuit between cooling fan mode relay, cooling fan relay No. 2, and PCM harness connector C1 terminal No. 5 (Dark Blue wire). (Scheme 5) PCM is located under left side of instrument panel, near steering column. Repair circuit as necessary, then go to step 12. If circuit is okay, go to step 9.
8. Check for open or short to ground in coil feed circuit for cooling fan mode relay and cooling fan relay No. 2. Repair circuit as necessary, then go to step 12. If circuit is okay, go to step 10.
9. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step 12. If connector is okay, go to step 11.
10. Repair short to ground in cooling fan motor supply voltage circuit. See WIRING DIAGRAMS article. After repairs, go to step 12.
11. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
12. Using scan tool, clear DTCs. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, system is okay. If scan tool does not indicate that this test ran and passed, go to step 2.

Diagnostic Procedure (Century, Impala & Monte Carlo)

1. Perform engine cooling diagnostic system check. See «ENGINE COOLING DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__engine-cooling-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing engine cooling diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, command high speed cooling fans on and off. Listen for cooling fan relay operation. Cooling fan relays are located in underhood fuse block. Cooling fan relays No. 2 and 3 should operate. If relays turn on and off with each command, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). If operation is not as specified, go to next step.
3. Turn ignition off. Remove cooling relay No. 3. Turn ignition on. Connect a test light between ground and coil feed circuit. If test light illuminates, go to next step. If test light does not illuminate, go to step 10.
4. Connect test light between control circuit and battery feed circuit of cooling fan relay No. 3. Using scan tool, command high speed cooling fans on and off. If test light turns on and off with each command, go to step 9. If test light does not respond as specified, go to next step.
5. If test light remains illuminated with each command, go to step 7. If test light does not remain illuminated with each command, go to next step.
6. Check for open or short to voltage in high speed cooling fan relay control circuit between cooling fan relays No. 2 and 3, and PCM harness connector C1 terminal No. 5 (Dark Blue wire). (Scheme 5) See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Repair circuit as necessary, then go to step 12. If circuit is okay, go to step 9.
7. Check for short to ground in high speed cooling fan relay control circuit between cooling fan relays No. 2 and 3, and PCM harness connector C1 terminal No. 5 (Dark Blue wire). (Scheme 5) See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Repair circuit as necessary, then go to step 12. If circuit is okay, go to step 9.
8. Check for open or short to ground in coil feed circuit for cooling fan relays No. 2 and 3. Repair circuit as necessary, then go to step 12. If circuit is okay, go to step 10.
9. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step 12. If connector is okay, go to step 11.
10. Repair short to ground in cooling fan motor supply voltage circuit. See WIRING DIAGRAMS article. After repairs, go to step 12.
11. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
12. Using scan tool, clear DTCs. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, system is okay. If scan tool does not indicate that this test ran and passed, go to step 2.

Diagnostic Procedure (Grand Prix)

1. Perform engine cooling diagnostic system check. See «ENGINE COOLING DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__engine-cooling-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing engine cooling diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, command high speed cooling fans on and off. Listen for cooling fan relay operation. Cooling fan relays are located in underhood fuse block. COOL FAN relay and COOL FAN 2 relay should operate. If relays turn on and off with each command, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). If operation is not as specified, go to next step.
3. Turn ignition off. Remove COOL FAN 2 relay. Turn ignition on. Connect a test light between ground and coil feed circuit. If test light illuminates, go to next step. If test light does not illuminate, go to step 8.
4. Connect test light between control circuit and battery feed circuit of COOL FAN 2 relay. Using scan tool, command high speed cooling fans on and off. If test light turns on and off with each command, go to step 9. If test light does not respond as specified, go to next step.
5. If test light remains illuminated with each command, go to step 7. If test light does not remain illuminated with each command, go to next step.
6. Check for open or short to voltage in high speed cooling fan relay control circuit between COOL FAN relay, COOL FAN 2 relay, and PCM harness connector C1 terminal No. 5 (Dark Blue wire). (Scheme 6) See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Repair circuit as necessary, then go to step 12. If circuit is okay, go to step 9.
7. Check for short to ground in high speed cooling fan relay control circuit between COOL FAN relay, COOL FAN 2 relay, and PCM harness connector C1 terminal No. 5 (Dark Blue wire). (Scheme 2)and (Scheme 5). Repair circuit as necessary, then go to step 12. If circuit is okay, go to step 9.
8. Check for open or short to ground in coil feed circuit for COOL FAN relay and COOL FAN 2 relay. Repair circuit as necessary, then go to step 12. If circuit is okay, go to step 10.
9. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step 12. If connector is okay, go to step 11.
10. Repair short to ground in cooling fan motor supply voltage circuit. See WIRING DIAGRAMS article. After repairs, go to step 12.
11. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
12. Using scan tool, clear DTCs. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, system is okay. If scan tool does not indicate that this test ran and passed, go to step 2.

Intermittent can be caused by poor connection, rubbed-through wire insulation, or a wire broken inside the insulation. Check connectors for backed-out terminals, improper mating, broken lock, damaged terminal or poor terminal to wire connection.

Using FREEZE FRAME and/or FAILURE RECORDS data mode may aid in locating an intermittent condition. If DTC cannot be duplicated, information included in FREEZE FRAME and/or FAILURE RECORDS data can be useful in determining how many miles since DTC set. FAIL COUNTER and PASS COUNTER can also be used to determine how many ignition cycles diagnostic reported a pass or a fail condition. To isolate when DTC failed, operate vehicle within same freeze frame conditions (RPM, load, vehicle speed, temperature, etc.).

Vehicle speed is signaled to PCM by Vehicle Speed Sensor (VSS). Sensor is a Permanent Magnet (PM) generator mounted to transaxle case extension. PM generator produces AC voltage as speed sensor rotor teeth pass sensor's magnetic field. PCM converts AC voltage into a digital signal. PCM uses vehicle speed to determine shift timing, torque converter clutch apply and release, and gear ratio calculations. VSS voltage will vary from .5 volt AC at 100 RPM to more than 200 volts AC at 6000 RPM. VSS resistance value is 981-1864 ohms. DTC P0502 will set if PCM detects a low vehicle speed when vehicle has high engine speed in Drive.

DTC will run under the following conditions

1. Transaxle is not in Park or Neutral.
2. DTCs P0106, P0107, P0108, P1106, P1107, P0121, P0122, P0123, P0716, P0717 or P1810 are not present.
3. Input shaft speed is more than 1500 RPM.
4. Throttle angle is more than 12 percent.
5. Engine torque is 40-150 ft. lbs (54-203 N.m).

DTC will set when output shaft speed is less than 150 RPM for 2.5 seconds.

1. Perform OBD system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records for reference. Data will be lost when DTCs are cleared later in this test. Raise and support vehicle. CAUTION: To prevent damage to drive axles, support lower control arms in normal horizontal position.
2. Start engine and let idle. Place gearshift lever in "D" position. Select OUTPUT SPEED on scan tool. With drive wheels rotating, if transaxle output speed does not increase when wheel speed increases, go to next step. If transaxle output speed increases when wheel speed increases, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). If transaxle output speed does not increase when wheel speed increases, go to next step.
3. Turn ignition off. Disconnect PCM harness connector C1. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Select AC volts on DVOM. Connect DVOM between PCM harness connector C1 terminals No. 64 (Yellow wire) and No. 65 (Yellow wire on Alero and Grand Am; Purple wire on all other models). (Scheme 5)or (Scheme 6). Turn ignition on. Rotate right front drive wheel and observe DVOM display. If voltage is more than.4 volt, go to step 15. If voltage is less than.4 volt, go to next step.
4. Measure resistance between PCM harness connector C1 terminals No. 64 (Yellow wire) and No. 65 (Yellow wire on Alero and Grand Am; Purple wire on all other models). If resistance is 1650-3180 ohms (on Century, Grand Prix, Impala and Monte Carlo) or 1530-1870 ohms (on Alero, Grand Am and Malibu), go to step 8. If resistance is not as specified, go to next step.
5. If resistance of complete VSS circuit is more than 3180 ohms (on Century, Grand Prix, Impala and Monte Carlo) or more than 1870 ohms (on Alero, Grand Am and Malibu), go to step 11. If resistance of complete VSS circuit is not more than 3180 ohms (on Century, Grand Prix, Impala and Monte Carlo) or not more than 1870 ohms (on Alero, Grand Am and Malibu), go to next step.
6. Disconnect VSS connector at transaxle. Check for short between signal and ground circuits. If signal and ground circuits are shorted together, go to next step. If signal and ground circuits are okay, go to step 14.
7. Repair short between signal and ground circuits. After repairs, go to step 16.
8. Check signal circuit for short to ground. Repair as necessary. After repairs, go to step 16. If signal circuit is okay, go to next step.
9. Reconnect PCM connector. Select DC volts on DVOM. Connect DVOM leads to VSS connector terminals. Turn ignition on, engine off. If voltage is more than one volt, go to next step. If voltage is one volt or less, go to step 13.
10. Repair short to voltage in signal circuit. After repairs, go to step 16.
11. Check signal circuit for open between PCM and VSS. Repair as necessary. After repairs, go to step 16. If signal circuit is okay, go to next step.
12. Check ground circuit for open between PCM and VSS. Repair as necessary. After repairs, go to step 16. If ground circuit is okay, go to step 14.
13. Remove VSS. Check for damaged or incorrect VSS. Check for damaged speed sensor rotor. Check for incorrect alignment of VSS and rotor. If a problem is found, repair as necessary, then go to step 16. If a problem is not found, go to next step.
14. Replace VSS. After repairs, go to step 16.
15. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
16. Using scan tool, clear DTCs. Test drive vehicle until transaxle output speed is more than 250 RPM for 3 seconds. If DTC P0502 is not present, repair is complete. If DTC P0502 is still present, go to step 1.

Check for DTC P0705 (transaxle range switch). This DTC will affect transaxle upshifts and may cause a false DTC P0502. Check for Electromagnetic Interferences (EMI) induced on VSS circuits by a misrouted wiring harness along spark plug wires. Check for bent, backed out or damaged terminals, or misaligned connectors. Check for poor terminal tension. Check for chafed wiring or broken wire inside insulation. When diagnosing for intermittent short or open condition, wiggle wiring harness while observing scan tool for change in value. Ensure VSS is secured to transaxle case extension.

Vehicle speed is signaled to PCM by Vehicle Speed Sensor (VSS). Sensor is a Permanent Magnet (PM) generator mounted to transaxle case extension. PM generator produces AC voltage as speed sensor rotor teeth pass sensor's magnetic field. PCM converts AC voltage into a digital signal. PCM uses vehicle speed to determine shift timing, TCC apply and release, and gear ratio calculations. VSS voltage will vary from .5 volt AC at 100 RPM to more than 200 volts AC at 6000 RPM. VSS resistance value is 981-1864 ohms. DTC P0503 will set if PCM detects large change in vehicle speed in short period of time.

PCM will run diagnostic for this DTC under the following conditions

1. Transaxle is not in Park or Neutral.
2. No DTC P0502 or P1810.
3. Engine speed is more than 500 RPM for 5 seconds and not in fuel shut off mode.
4. Time since last gear change is more than 6 seconds.
5. No output speed increase more than 250 RPM in 2 seconds.

DTC will set when output shaft speed drops more than 1500 RPM in 2 seconds.

MIL will illuminate after 2 consecutive ignition cycles with first failure signal. PCM commands maximum line pressure and disables shift adapts. PCM calculates vehicle speed using input speed sensor information and commanded gear.

1. Perform OBD system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records for reference. Data will be lost when DTCs are cleared later in this test. Raise and support vehicle. CAUTION: To prevent damage to drive axles, support lower control arms in normal horizontal position.
2. Start engine and let idle. Place gear selector in "D" position. Select TRANS. OSS RPM on scan tool. With drive wheels rotating, if transaxle OSS RPM speed does not increase when wheel speed increases, go to next step. If transaxle OSS RPM speed increases when wheel speed increases, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
3. Turn ignition off. Disconnect PCM harness connector C1. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Select AC volts on DVOM. Connect DVOM between PCM harness connector C1 terminals No. 64 (Yellow wire) and No. 65 (Yellow wire on Alero and Grand Am; Purple wire on all other models). (Scheme 5)or (Scheme 6). Turn ignition on. Rotate right front drive wheel and observe DVOM display. If voltage is more than.4 volt, go to step 15. If voltage is less than.4 volt, go to next step.
4. Measure resistance between PCM harness connector C1 terminals No. 64 (Yellow wire) and No. 65 (Yellow wire on Alero and Grand Am; Purple wire on all other models). If resistance is 1650-3180 ohms (on Century, Grand Prix, Impala and Monte Carlo) or 1530-1870 ohms (on Alero, Grand Am and Malibu), go to step 8. If resistance is not as specified, go to next step.
5. If resistance of complete VSS circuit is more than 3180 ohms (on Century, Grand Prix, Impala and Monte Carlo) or more than 1870 ohms (on Alero, Grand Am and Malibu), go to step 11. If resistance of complete VSS circuit is not more than 3180 ohms (on Century, Grand Prix, Impala and Monte Carlo) or not more than 1870 ohms (on Alero, Grand Am and Malibu), go to next step.
6. Disconnect VSS connector at transaxle. Check for short between signal and ground circuits. If signal and ground circuits are shorted together, go to next step. If signal and ground circuits are okay, go to step 14.
7. Repair short between signal and ground circuits. After repairs, go to step 16.
8. Check signal circuit for short to ground. If signal circuit is shorted to ground, repair as necessary. After repairs, go to step 16. If signal circuit is okay, go to next step.
9. Reconnect PCM connector. Select DC volts on DVOM. Connect DVOM leads to VSS connector terminals. Turn ignition on, engine off. If voltage is more than one volt, go to next step. If voltage is one volt or less, go to step 13.
10. Repair short to voltage in signal circuit. After repairs, go to step 16.
11. Check signal circuit for open between PCM and VSS. Repair as necessary. After repairs, go to step 16. If signal circuit is okay, go to next step.
12. Check ground circuit for open between PCM and VSS. Repair as necessary. After repairs, go to step 16. If ground circuit is okay, go to step 14.
13. Remove VSS. Check for damaged or incorrect VSS. Check for damaged speed sensor rotor. Check for incorrect alignment of VSS and rotor. If a problem is found, repair as necessary, then go to step 16. If a problem is not found, go to next step.
14. Replace VSS. After repairs, go to step 16.
15. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
16. Using scan tool, clear DTCs. Test drive vehicle under conditions for setting DTC P0503. If DTC P0503 is not present, repair is complete. If DTC P0503 is still present, go to step 1.

Condition may be intermittent. Inspect wiring harness for poor connections at PCM, transaxle 20-pin connector and vehicle speed sensor. Check for bent, backed out or damaged terminals, or misaligned connectors. Check for poor terminal tension or chafed wires. Inspect engine wiring harness for pinched wires which may cause an intermittent. When diagnosing for intermittent short or open condition, wiggle wiring harness while observing scan tool for change in value. Check for Electromagnetic Interferences (EMI) induced on VSS circuits by a misrouted wiring harness along spark plug wires. Ensure VSS is secured to transaxle case extension. Too much runout in final drive carrier may set DTC P0503. If VSS and circuitry are okay, repair final drive carrier as necessary.

PCM controls idle speed with an Idle Air Control (IAC) valve to a calculated RPM based on sensor inputs and actual engine RPM. PCM moves IAC valve in or out to vary amount of airflow into intake manifold and thus decrease or increase idle RPM. PCM commands IAC in counts. A higher count, allows more air to by-pass throttle plate (higher idle).

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0171, P0172, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0401, P0403, P0404, P0405, P0443, P1121, P01404, or P1441 are not set.
2. Engine run time is more than 2 minutes.
3. Engine Coolant Temperature (ECT) is more than 158°F (70°C).
4. Intake Air Temperature (IAT) is more than -.4°F (-18°C).
5. Barometric Pressure (BARO) is more than 70 kPa.
6. Ignition voltage is 9-18 volts.
7. Throttle Position (TP) sensor is less than 1.5 percent.
8. Vehicle speed is less than 3 MPH.
9. Above conditions are present for 5 seconds.

DTC will set when actual engine speed is 100 RPM less than desired engine speed. Diagnostic must fail 4 consecutive tests per key cycle.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Start engine. Ensure all accessories are turned off. Using scan tool RPM control function, slowly increment engine speed to 1800 RPM, then to 600 RPM, then to 1800 RPM. If engine speed stabilizes to within 100 RPM of commanded RPM during test, go to next step. If engine speed does not stabilize to within 100 RPM of commanded RPM during test, go to step 4 .
3. Using scan tool, observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within conditions for setting DTC or as close to FREEZE FRAME/FAILURE RECORDS data as possible. If DTC fails this ignition cycle, go to next step. If DTC does not fail this ignition cycle, go to «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) .
4. Turn ignition off. Disconnect IAC valve harness connector located on throttle body. Connect IAC Motor Driver (J 37027-A) to IAC valve. Start engine. Using IAC motor driver, command IAC valve in until about 600 RPM is reached, then out until about 1800 RPM is reached. Return engine speed to desired idle speed as indicated on scan tool. If engine speed steadily increased and decreased to specified speeds when commanded, go to next step. If engine speed did not steadily increase and decrease to specified speeds when commanded, go to step 11 .
5. Turn ignition off. Using Connector Test Adapter Kit (J 35616-A), connect a test light between ground and one of the IAC valve harness connector terminals. Start engine. 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 scan tool until IAC counts start to increment. While IAC counts are incrementing, observe test light. Return engine speed to desired idle speed as indicated on scan tool. Repeat procedure for remaining 3 IAC valve circuits. If test light remained on (never flashing) while IAC counts were incrementing for any of the IAC valve circuits, go to step 10 . If test light did not remain on, go to next step.
6. If test light remained off (never flashing) while IAC counts were incrementing for any of the IAC valve circuits, go to step 9 . If test light did not remain off, go to next step.
7. Using Connector Test Adapter Kit (J 35616-A), connect test light between IAC valve harness connector terminals "C" (Light Blue/Black wire) and "D" (Light Blue/White wire). 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 scan tool until IAC counts start to increment. While IAC counts are incrementing, observe test light. Return engine speed to desired idle speed as indicated on scan tool. Repeat procedure with test light connected between IAC valve harness connector terminals "A" (Light Green/Black wire) and "B" (Light Green/White wire). If test light remained on (never flashing) while IAC counts were incrementing for either test, go to next step. If test light did not remain on, go to step 15 .
8. Inspect IAC valve harness connector for poor connections. Repair connector as necessary, then go to step 16 . If connector is okay, go to «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) .
9. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location) . Check for open or short to ground in IAC valve circuit where test light remained off. See «IAC VALVE CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table. Repair circuit as necessary, then go to step 16 . If circuit is okay, go to step 12 .
10. Turn ignition on. Check for short to voltage in IAC valve circuit where test light remained on. See «IAC VALVE CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table. Repair circuit as necessary, then go to step 16 . If circuit is okay, go to step 12 .
11. Inspect throttle body for damage and tampering. Check throttle lever screw for tampering (if equipped). Check for restricted air intake system. Remove IAC valve. Check for clogged IAC passages, excessive deposits on throttle plate, throttle bore or IAC valve pintle. If a problem is found, repair as necessary, then go to step 16 . If no problem is found, go to step 13 .
12. Inspect PCM harness connector for poor connections. If a problem is found, repair as necessary, then go to step 16 . If no problem is found, go to step 15 .
13. Inspect IAC valve harness connector for poor connections. Repair connector as necessary, then go to step 16 . If connector is okay, go to next step.
14. Replace IAC valve. After repairs, go to step 16 .
15. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . After repairs, go to next step.
16. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2 . If DTC does not reset, go to next step.
17. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs, system is okay.

IAC VALVE CIRCUIT IDENTIFICATION

Check for the following conditions

1. Restricted air intake system.
2. Proper operation and installation of all air intake components. Check for collapsed, clogged, or loose air intake ducts, a clogged air filter, and proper operation of mass airflow sensor.
3. A tampered with or damaged throttle stop screw.
4. A tampered with or damaged throttle plate, throttle shaft, or throttle linkage.
5. Objects blocking IAC passage or throttle bore.
6. Excessive deposits in IAC passage or on IAC valve pintle.
7. Excessive deposits in throttle bore or on throttle plate.
8. Vacuum leaks. A low or unstable idle condition could be caused by a non-IAC system condition that can not be overcome by IAC valve.
9. If condition is determined to be intermittent, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.

The Idle Air Control (IAC) valve is controlled by the Powertrain Control Module (PCM). PCM uses the IAC to maintain a desired idle speed, which varies depending on input to PCM. Scan tool reads IAC valve pintle position in counts. The higher the counts, the more air that is allowed to by-pass the throttle plate.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0171, P0172, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0401, P0403, P0404, P0405, P0443, P1121, P01404, or P1441 are not set.
2. Engine run time is more than 2 minutes.
3. Engine Coolant Temperature (ECT) is more than 158°F (70°C).
4. Intake Air Temperature (IAT) is more than -.4°F (-18°C).
5. Barometric Pressure (BARO) is more than 70 kPa.
6. Ignition voltage is 9-18 volts.
7. Throttle Position (TP) sensor is less than 1.5 percent.
8. Vehicle speed is less than 3 MPH.
9. Above conditions are present for 5 seconds.

DTC will set when actual engine speed is 1500 RPM more than desired engine speed. Diagnostic must fail 4 consecutive tests per key cycle.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Start engine. Ensure all accessories are turned off. Using scan tool RPM control function, slowly increment engine speed to 1800 RPM, then to 600 RPM, then to 1800 RPM. If engine speed stabilizes to within 150 RPM of commanded RPM during test, go to next step. If engine speed does not stabilize to within 150 RPM of commanded RPM during test, go to step 4.
3. Using scan tool, observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within conditions for setting DTC or as close to FREEZE FRAME/FAILURE RECORDS data as possible. If DTC fails this ignition cycle, go to next step. If DTC does not fail this ignition cycle, go to «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
4. Turn ignition off. Disconnect IAC valve harness connector located on throttle body. Connect IAC Motor Driver (J 37027-A) to IAC valve. Start engine. Using IAC motor driver, command IAC valve in until about 600 RPM is reached, then out until about 1800 RPM is reached. Return engine speed to desired idle speed as indicated on scan tool. If engine speed steadily increased and decreased to specified speeds when commanded, go to next step. If engine speed did not steadily increase and decrease to specified speeds when commanded, go to step 11.
5. Turn ignition off. Using Connector Test Adapter Kit (J 35616-A), connect a test light between ground and one of the IAC valve harness connector terminals. Start engine. 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 scan tool until IAC counts start to increment. While IAC counts are incrementing, observe test light. Return engine speed to desired idle speed as indicated on scan tool. Repeat procedure for remaining 3 IAC valve circuits. If test light remained on (never flashing) while IAC counts were incrementing for any of the IAC valve circuits, go to step 10. If test light did not remain on, go to next step.
6. If test light remained off (never flashing) while IAC counts were incrementing for any of the IAC valve circuits, go to step 9. If test light did not remain off, go to next step.
7. Using Connector Test Adapter Kit (J 35616-A), connect test light between IAC valve harness connector terminals "C" (Light Blue/Black wire) and "D" (Light Blue/White wire). 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 scan tool until IAC counts start to increment. While IAC counts are incrementing, observe test light. Return engine speed to desired idle speed as indicated on scan tool. Repeat procedure with test light connected between IAC valve harness connector terminals "A" (Light Green/Black wire) and "B" (Light Green/White wire). If test light remained on (never flashing) while IAC counts were incrementing for either test, go to next step. If test light did not remain on, go to step 15.
8. Inspect IAC valve harness connector for poor connections. Repair connector as necessary, then go to step 16. If connector is okay, go to «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
9. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Check for open or short to ground in IAC valve circuit where test light remained off. See «IAC VALVE CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table under DTC P0506: IDLE SPEED - LOW. (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 16. If circuit is okay, go to step 12.
10. Turn ignition on. Check for short to voltage in IAC valve circuit where test light remained on. See «IAC VALVE CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table under DTC P0506: IDLE SPEED - LOW. Repair circuit as necessary, then go to step 16. If circuit is okay, go to step 12.
11. Inspect throttle body for damage and tampering. Check throttle lever screw for tampering (if equipped). Check for vacuum leaks, faulty or incorrectly installed PCV valve and hose, throttle shaft binding, throttle linkage binding or cruise control linkage binding. Remove IAC valve. Check for debris in IAC passages, excessive deposits on throttle plate, throttle bore or IAC valve pintle. If a problem is found, repair as necessary, then go to step 16. If no problem is found, go to step 13.
12. Inspect PCM harness connector for poor connections. If a problem is found, repair as necessary, then go to step 16. If no problem is found, go to step 15.
13. Inspect IAC valve harness connector for poor connections. Repair connector as necessary, then go to step 16. If connector is okay, go to next step.
14. Replace IAC valve. After repairs, go to step 16.
15. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
16. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
17. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Check for the following conditions

1. Correct PCV valve, properly installed and proper operation of PCV valve.
2. Proper operation and installation of all air intake components.
3. Proper installation and operation of mass airflow sensor.
4. A tampered with or damaged throttle stop screw.
5. A tampered with or damaged throttle plate, throttle shaft, throttle linkage, or cruise control linkage, if equipped.
6. A 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. A high or unstable idle condition could be caused by a non-IAC system problem that cannot be overcome by IAC valve.
10. If condition is determined to be intermittent, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.

The PCM monitors the high side refrigerant pressure via a A/C refrigerant pressure sensor. When the pressure is high the signal voltage is high. When the pressure is low, signal voltage is low. When pressure is high, PCM commands the cooling fans on. When pressure is too high or too low, PCM will not allow the A/C compressor clutch to engage.

Conditions For Running DTC

1. Engine is running.
2. A/C has been requested.

Conditions For Setting DTC

1. PCM detects the signal circuit is less than 5 counts (0.09 V) or greater than 250 counts (4.90 V).
2. The condition exists for 3 seconds.

Action Taken When DTC Sets

1. PCM will not illuminate the Malfunction Indicator Light (MIL).
2. PCM stores the failure records.
3. A/C compressor clutch is disabled.

Conditions For Clearing DTC

1. DTC will become history if the PCM no longer detects a failure.
2. The history DTC will clear after 40 fault-free ignition cycles.
3. The DTC can be cleared with a scan tool.

Test Description

The numbers below refer to the step numbers on the diagnostic procedure.

1. 4 - Tests for the proper operation of the circuit in the low voltage range.
2. 5 - Tests for the proper operation of the circuit in the high voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to ground.
3. 6 - Tests for a short to voltage in the 5-volt reference circuit.
4. 7 - Tests for a high resistance or an open in the low reference circuit.
5. 16 - Perform programming procedure for PCM.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn OFF the ignition. Inspect the A/C compressor for free rotation operation. Start engine. Place HVAC Control Module in the OFF position. Does the A/C compressor operate? If yes, diagnose A/C compressor clutch. If no, go to next step.
3. Install a scan tool. Turn ignition on, with engine off. With scan tool, observe the A/C High Side Pressure parameter in the Powertrain, Engine Data-2 list. Does the scan tool indicate that the A/C High Side Pressure parameter is within 0.09-4.90 volts? If yes, diagnose for intermittent and poor connections in wiring system. If no, go to next step.
4. Turn OFF the ignition. Disconnect the A/C refrigerant pressure sensor. Turn ignition on, with engine off. With scan tool, observe the A/C High Side Pressure parameter. Does the scan tool indicate that the A/C High Side Pressure parameter is less than 0.09 volt? If yes, go to next step. If no, go to step 11 .
5. Turn OFF the ignition. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the A/C refrigerant pressure sensor and signal circuit of the A/C refrigerant pressure sensor. Turn ignition on, with engine off. With scan tool, observe the A/C High Side Pressure parameter. Does the scan tool indicate that the A/C High Side Pressure parameter is greater than 4.9 volts? If yes, go to next step. If no, go to step 9 .
6. Disconnect the fused jumper wire. Measure voltage between the 5-volt reference circuit of the A/C refrigerant pressure sensor and low reference circuit of the A/C refrigerant pressure sensor. Does the voltage measure less than 5.1 volt? If yes, go to next step. If yes, go to step 8 .
7. Turn OFF the ignition. Disconnect negative battery cable. Measure resistance from the low reference circuit of the A/C refrigerant pressure sensor to a good ground. Does the resistance measure less than 5 ohms? If yes, go to step 13 . If no, go to step 12 .
8. Test the 5-volt reference circuit of the A/C refrigerant pressure sensor for a short to voltage. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 14 .
9. Test the 5-volt reference circuit of the A/C refrigerant pressure sensor for a short to ground, a high resistance, or an open. Did you find and correct the condition? If yes, go to step 17 . If no, go to next step.
10. Test the signal circuit of the A/C refrigerant pressure sensor for a short to ground, a high resistance, or an open. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 14 .
11. Test the signal circuit of the A/C refrigerant pressure sensor for a short to voltage. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 14 .
12. Disconnect the PCM harness connector. Test the low reference circuit of the A/C refrigerant pressure sensor for a high resistance or an open. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 14 .
13. Inspect for poor connections at the harness connector of the A/C refrigerant pressure sensor. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 15 .
14. Inspect for poor connections at the PCM harness connector. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 16.
15. Replace the A/C refrigerant pressure sensor. After replacing sensor, go to step 17 .
16. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . After repairs, go to next step.
17. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. Using scan tool, observe SPECIFIC DTC information until this test runs. If this DTC resets, go to step 2 . If this DTC does not reset, system is okay.

PCM monitors system voltage on PCM ignition feed circuit. If system voltage is out of range, DTC P0560 will set.

PCM will run diagnostic for this DTC under the following conditions

1. System voltage is less than 11 volts.
2. Engine speed is more than 1500 RPM.
3. Vehicle speed is less than 25 MPH.

DTC will set when PCM detects system voltage is out of range for 2 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, observe IGNITION 1 SIGNAL parameter in PCM data list. If scan tool displays more than 11 volts, go to step 6. If scan tool does not display more than 11 volts, go to next step.
3. Measure battery voltage. Compare battery voltage to IGNITION 1 SIGNAL voltage displayed on scan tool. If difference is more than.5 volt, go to next step. If difference is not more than.5 volt, go to TEST A: CHARGING SYSTEM TEST under SYSTEM TESTS in GENERATORS & REGULATORS - "J", "N" & "W" BODIES article in STARTING & CHARGING SYSTEMS.
4. Check for high resistance between battery and PCM harness connector C1 terminal No. 20 (Orange wire). See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). See WIRING DIAGRAMS article. Repair circuit as necessary, then go to step 7. If circuit is okay, go to next step.
5. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step 7. If connector is okay, go to next step.
6. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repairs, go to next step.
7. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. Using scan tool, observe SPECIFIC DTC information until this test runs. If this DTC resets, go to step 2. If this DTC does not reset, system is okay.

PCM uses an Electrically Erasable Programmable Read Only Memory (EEPROM). EEPROM contains program information and calibrations required for engine, transaxle, and powertrain diagnostics operation.

If PCM detects an internal program fault (check sum error), DTC P0601 will set.

Diagnostic Procedures

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . After replacing PCM, repeat powertrain diagnostic system check.

DTC P0601 indicates that contents of EEPROM have changed since PCM was programmed. Only possible repair is replacement and programming of PCM.

PCM uses an Electrically Erasable Programmable Read Only Memory (EEPROM). EEPROM contains program information and calibrations required for engine, transaxle, and powertrain diagnostics operation.

DTC P0602 will set if PCM does not contain correct program(s) required to operate vehicle.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
2. Using special equipment, program PCM with correct software. Using scan tool, retest for this DTC. If DTC resets, go to next step. If DTC does not reset, system is okay.
3. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . After replacing PCM, repeat powertrain diagnostic system check.

Ignition voltage is supplied directly to Malfunction Indicator Light (MIL). PCM controls MIL by grounding the control circuit via an internal switch called a driver. The driver supplies ground to the component being controlled. Each driver has a fault line which is monitored by PCM. When PCM is commanding a component, voltage of control circuit should be low (near zero volts). When PCM is commanding the control circuit to a component off, voltage of control circuit should be high (near battery voltage). If the fault detection circuit senses a voltage other than what is expected, the fault line status changes causing DTC to set.

PCM will run diagnostic for this DTC when ignition is on. DTC will set when an improper voltage level has been detected on the MIL control circuit for at least 30 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, command MIL on and off. If MIL turns on and off with each command, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). If MIL does not turn on and off with each command, go to next step.
3. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Turn ignition on. Check MIL. If MIL is off, go to next step. If MIL is on, go to step 5.
4. Using a fused jumper wire connected to ground, probe MIL control circuit at PCM harness connector C2 terminal No. 5 (Brown/White wire). (Scheme 5)or (Scheme 6). Check MIL. If MIL is on, go to step 6. If MIL is off, go to step 7.
5. Repair short to ground in MIL control circuit. After repairs, go to step 9.
6. Check for poor connections at PCM connector. Repair as necessary. After repairs, go to step 9. If connection is okay, go to step 8.
7. Check for open ignition feed circuit to MIL. See WIRING DIAGRAMS article. Check control circuit for open or short to battery voltage. Repair as necessary. After repairs, go to step 9.
8. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
9. Using scan tool, clear DTCs. Start and warm engine to normal operating temperature. Select SPECIFIC DTC INFO for this DTC. Operate vehicle within conditions noted in FAILURE RECORDS data. If scan tool displays that this DTC FAILED THIS IGN, return to step 2. If scan tool does not display that this DTC FAILED THIS IGN, go to next step.
10. Using scan tool, select CAPTURE INFO and REVIEW INFO. If any other DTCs are preset, diagnose affected DTCs. If no other DTCs are set, system is okay.

If ignition feed circuit is suspected of being open, inspect other bulbs which are powered by the same circuit. If condition is intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Manifold Absolute Pressure (MAP) sensor measures changes in intake manifold pressure (vacuum). MAP sensor provides a signal to PCM on signal circuit which is relative to pressure changes in intake manifold. With low manifold absolute pressure such as during idle or deceleration, PCM should detect a low MAP sensor signal voltage. With high manifold absolute pressure such as ignition on, with engine off or wide open throttle, PCM should detect a high MAP sensor signal voltage. If PCM detects a MAP sensor signal voltage that is intermittently high, DTC P1106 will set.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0121, P0122, or P0123 are not set.
2. Engine has been running for a length of time that is determined by start-up coolant temperature. The time ranges from 2 minutes at less than 86°F (30°C), to one second at more than 86°F (30°C).
3. Throttle angle is less than 2 percent when engine speed is less than 3000 RPM.
4. Throttle angle is less than 30 percent when engine speed is more than 3000 RPM.

DTC will set when MAP sensor voltage is intermittently more than 4.2 volts.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, start engine. Check if DTC P0108 or P1635 is also set. If DTC P0108 or P1635 is also set, diagnose DTC P0108 or P1635 before proceeding. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If DTC P0108 or P1635 is not set, go to next step.
3. If scan tool indicates that MAP sensor voltage is more than 4.2 volts, go to step 5. If scan tool does not indicate that MAP sensor voltage is more than 4.2 volts, go to next step.
4. While observing MAP sensor voltage on scan tool, wiggle MAP sensor harness connector, PCM harness connector and wiring harness related to MAP sensor. If scan tool indicates that MAP sensor voltage is steady at more than 4.2 volts, go to next step. If scan tool does not indicate that MAP sensor voltage is steady at more than 4.2 volts, go to «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
5. Turn ignition off. Disconnect MAP sensor harness connector. (Scheme 10)or (Scheme 15). Turn ignition on. If scan tool indicates that MAP sensor voltage is less than.1 volt, go to next step. If scan tool does not indicate that MAP sensor voltage is less than.1 volt, go to step 8.
6. Measure voltage between MAP sensor harness connector terminals "A" (Orange/Black wire) and "C" (Gray wire). If voltage is 4.7-5.2 volts, go to step 11. If voltage is not 4.7-5.2 volts, go to next step.
7. If voltage is more than 5.2 volts, go to step 10. If voltage is not more than 5.2 volts, go to step 9.
8. Check for short to voltage in signal circuit (Light Green wire) between MAP sensor harness connector terminal "B" and PCM harness connector C2 terminal No. 25. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 13. If circuit is okay, go to step 12.
9. Check for open in low reference circuit (Orange/Black wire) between MAP sensor harness connector terminal "A" and PCM harness connector C1 terminal No. 13. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 13. If circuit is okay, go to step 12.
10. Check for short to battery voltage in 5-volt reference circuit (Gray wire) between MAP sensor harness connector terminal "C" and PCM harness connector C1 terminal No. 10. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 13. If circuit is okay, go to step 12.
11. Inspect MAP sensor harness connector for poor connections. Repair connector as necessary, then go to step 13. If connector is okay, go to «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
12. Inspect PCM harness connectors for poor connections. Repair connector(s) as necessary, then go to next step. If connectors are okay, go to «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
13. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
14. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Inspect MAP sensor vacuum source for leaks, restrictions or poor connections. If an intermittent condition exists, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Manifold Absolute Pressure (MAP) sensor measures changes in intake manifold pressure (vacuum). MAP sensor provides a signal to PCM on signal circuit which is relative to pressure changes in intake manifold. With low manifold absolute pressure such as during idle or deceleration, PCM should detect a low MAP sensor signal voltage. With high manifold absolute pressure such as ignition on, with engine off or wide open throttle, PCM should detect a high MAP sensor signal voltage. If PCM detects a MAP sensor signal voltage that is intermittently low, DTC P1107 will set.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0121, P0122, or P0123 are not set.
2. Ignition is on.
3. Throttle angle is more than zero percent when engine speed is less than 1000 RPM.
4. Throttle angle is more than 10 percent when engine speed is more than 1000 RPM.

DTC will set when MAP sensor voltage is intermittently less than .1 volt.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, start engine. Check if DTC P0107 or P1635 is also set. If DTC P0107 or P1635 is also set, diagnose DTC P0107 or P1635 before proceeding. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If DTC P0107 or P1635 is not set, go to next step.
3. If scan tool indicates that MAP sensor voltage is less than.1 volt, go to step 5. If scan tool does not indicate that MAP sensor voltage is less than.1 volt, go to next step.
4. Turn ignition off then on. While observing MAP sensor voltage on scan tool, wiggle MAP sensor harness connector, PCM harness connector and wiring harness related to MAP sensor. If scan tool indicates that MAP sensor voltage is steady at less than.1 volt, go to next step. If scan tool does not indicate that MAP sensor voltage is steady at less than.1 volt, go to «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
5. Turn ignition off. Disconnect MAP sensor harness connector. Turn ignition on. Measure voltage between ground and MAP sensor harness connector terminal "C" (Gray wire). If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step 7.
6. Connect a 3-amp fused jumper wire between MAP sensor harness connector terminal "C" (Gray wire) and "B" (Light Green wire). If scan tool indicates that MAP sensor voltage is about 5 volts, go to step 9. If scan tool does not indicate that MAP sensor voltage is about 5 volts, go to step 8.
7. Check for open or short to ground in 5-volt reference circuit (Gray wire) between MAP sensor harness connector terminal "C" and PCM harness connector C1 terminal No. 10. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 11. If circuit is okay, go to step 10.
8. Check for open or short to ground in signal circuit (Light Green wire) between MAP sensor harness connector terminal "B" and PCM harness connector C2 terminal No. 25. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 11. If circuit is okay, go to step 10.
9. Inspect MAP sensor harness connector for poor connections. Repair connector as necessary, then go to step 11. If connector is okay, go to «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
10. Inspect PCM harness connectors for poor connections. Repair connector(s) as necessary, then go to next step. If connectors are okay, go to «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
11. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
12. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Inspect MAP sensor vacuum source for leaks, restrictions or poor connections. If an intermittent condition exists, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Intake Air Temperature (IAT) sensor is a thermistor. PCM applies and reads a 5-volt reference signal to sensor. When air is cold, sensor resistance is high and PCM will read a high signal voltage. If air is warm, sensor resistance is low causing PCM to read low voltage.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0101, P0102, P0103, P0117, P0118, P0125, P0128, P0502, P0503, P1114, or P1115 are not set.
2. Vehicle speed is less than 35 MPH.
3. Mass airflow is less than 12 grams per second.
4. Engine Coolant Temperature (ECT) is more than 140°F (60°C).
5. Engine run time is more than 3 minutes.

DTC will set when IAT signal voltage indicates intake air temperature is intermittently less than -35°F (-37°C).

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, check for other DTCs. If DTC P0113 is also set, diagnose DTC P0113 before proceeding. See «DTC P0113: IAT SENSOR CIRCUIT - HIGH VOLTAGE»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). If DTC P0113 is not set, go to next step.
3. If DTC P1106, P1115, and/or P1121 is also set, go to step 6. If these DTCs are not set, go to next step.
4. Check for faulty low reference circuit (Black wire) connection at IAT sensor. Repair connector as necessary, then go to step 10. If connector is okay, go to next step.
5. Check for faulty signal circuit (Tan wire) connection at IAT sensor. Repair connector as necessary, then go to step 10. If connector is okay, go to next step.
6. Check for intermittent open in signal circuit (Tan wire) between IAT sensor harness connector terminal "B" and PCM harness connector C2 terminal No. 50. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 10. If circuit is okay, go to next step.
7. Check for intermittent short to voltage in signal circuit (Tan wire) between IAT sensor harness connector terminal "B" and PCM harness connector C2 terminal No. 50. Repair circuit as necessary, then go to step 10. If circuit is okay, go to next step.
8. Check for faulty ground circuit terminal connection at PCM. Repair connector as necessary, then go to step 10. If connection is okay, go to next step.
9. Check for intermittent open or faulty splice in low reference circuit (Black wire) between IAT sensor harness connector terminal "A" and PCM harness connector C1 terminal No. 17. If a problem is found, repair as necessary, then go to next step. If no problem is found, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
10. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
11. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

DTC P1112: IAT SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article.

Intake Air Temperature (IAT) sensor is a thermistor. PCM applies and reads a 5-volt reference signal to sensor. When air is cold, sensor resistance is high and PCM will read a high signal voltage. If air is warm, sensor resistance is low causing PCM to read low voltage.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0101, P0102, P0103, P0117, P0118, P0125, P0128, P0502, P0503, P1114, or P1115 are not set.
2. Engine run time is more than 10 seconds.
3. Vehicle speed is more than 25 MPH.

DTC will set when IAT signal voltage indicates intake air temperature is intermittently more than 275°F (135°C).

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, check for other DTCs. If DTC P0112 is also set, diagnose DTC P0112 before proceeding. See «DTC P0112: IAT SENSOR CIRCUIT - LOW VOLTAGE»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). If DTC P0112 is not set, go to next step.
3. Check for intermittent short to ground in signal circuit (Tan wire) between IAT sensor harness connector terminal "B" and PCM harness connector C2 terminal No. 50. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to next step. If circuit is okay, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
4. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
5. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Engine Coolant Temperature (ECT) sensor is a thermistor that varies resistance based on temperature. As temperature of sensor increases, resistance decreases. High temperature will result in a low signal voltage. DTC P1114 will set when PCM sees an intermittently low ECT sensor voltage.

PCM will run diagnostic for this DTC when engine has been running for more than 5 seconds. DTC will set when PCM detects an intermittently high ECT sensor voltage.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain diagnostic system check, go to next step.
2. Start engine. Using scan tool, check for other DTCs. If DTC P0117 is also set, diagnose DTC P0117 before proceeding. See «DTC P0117: ECT SENSOR CIRCUIT - LOW VOLTAGE»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). If DTC P0117 is not set, go to next step.
3. Turn ignition off then on. Using scan tool, observe ECT sensor temperature while wiggling harness connectors at ECT sensor and PCM. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). If scan tool indicates an abrupt change in value, go to step 6. If scan tool does not indicate an abrupt change in value, go to next step.
4. Using scan tool, observe ECT sensor temperature while wiggling wiring harness between ECT sensor and PCM. If scan tool indicates an abrupt change in value, go to step 7. If scan tool does not indicate an abrupt change in value, go to next step.
5. Using scan tool, observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine, and operate vehicle within conditions required to set DTC or as close to FREEZE FRAME/FAILURE RECORDS data as possible. If DTC resets, go to «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). If DTC does not reset, system is okay.
6. Repair connector or terminal as necessary. After repairs, go to step 8.
7. Repair wiring harness as necessary. After repairs, go to next step.
8. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
9. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

An ECT sensor or PCM which is intermittently shorted, open, or skewed is possible yet very unlikely. An intermittent short to ground in the ECT sensor signal circuit could result in a DTC P1114. If the low ECT voltage (high temperature) reading is present, additional sensor circuit voltage codes could be set. Refer to any non-intermittent DTCs that are set. Test ECT sensor at various temperature levels to check for a skewed sensor. See SENSOR OPERATING RANGE CHARTS - CARS article. A skewed sensor could result in poor driveability complaints. If an intermittent condition is suspected, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Engine Coolant Temperature (ECT) sensor is a thermistor or a variable resistor, that varies resistance based on temperature. As temperature of sensor increases, resistance decreases. High temperature will result in a low signal voltage.

PCM will run diagnostic for this DTC when engine is running. DTC will set when PCM detects an intermittently low ECT sensor temperature.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain diagnostic system check, go to next step.
2. Start engine. Using scan tool, check for other DTCs. If DTC P0118 is also set, diagnose DTC P0118 before proceeding. See «DTC P0118: ECT SENSOR CIRCUIT - HIGH VOLTAGE»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). If DTC P0118 is not set, go to next step.
3. Turn ignition off then on. Using scan tool, observe ECT sensor temperature while wiggling harness connectors at ECT sensor and PCM. If scan tool indicates an abrupt change in value, go to step 6. If scan tool does not indicate an abrupt change in value, go to next step.
4. Using scan tool, observe ECT sensor temperature while wiggling wiring harness between ECT sensor and PCM. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). If scan tool indicates an abrupt change in value, go to step 7. If scan tool does not indicate an abrupt change in value, go to next step.
5. Using scan tool, observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine, and operate vehicle within conditions required to set DTC or as close to FREEZE FRAME/FAILURE RECORDS data as possible. If DTC resets, go to «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). If DTC does not reset, system is okay.
6. Repair connector or terminal as necessary. After repairs, go to step 8.
7. Repair wiring harness as necessary. After repairs, go to next step.
8. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
9. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

An intermittent open or short to voltage in the ECT sensor signal circuit could result in a DTC P1115. If the high ECT voltage (low temperature) reading is present, additional sensor circuit voltage codes could be set. Refer to any non-intermittent DTCs that are set. Test ECT sensor at various temperature levels to check for a skewed sensor. See SENSOR OPERATING RANGE CHARTS - CARS article. A skewed sensor could result in poor driveability complaints. If an intermittent condition is suspected, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Throttle Position (TP) sensor is used by PCM to determine throttle plate angle for various engine management systems. TP sensor is a potentiometer type sensor with 3 circuits: a 5-volt reference circuit, a low reference circuit, and a signal circuit. Rotation of TP sensor rotor from closed throttle position to wide open throttle position provides PCM with a signal voltage from less than one volt to more than 4 volts through TP sensor signal circuit.

PCM will run diagnostic for this DTC when ignition is on. DTC will set when TP sensor intermittently indicates a TP sensor signal voltage of more than 4.9 volts for .5 second.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain diagnostic system check, go to next step.
2. Turn ignition off. Disconnect TP sensor harness connector. (Scheme 10), (Scheme 14) or (Scheme 16). Turn ignition on. Measure voltage between ground and TP sensor harness connector terminal "A" (Gray wire on Century, Grand Prix, Impala and Monte Carlo; Gray/Black wire on Alero, Grand Am and Malibu) While observing voltage, lightly touch and move all related engine wiring harnesses and connectors for all 5-volt reference circuits. See WIRING DIAGRAMS article. Any change in voltage indicates area where a short to voltage may be found. If a problem is found, repair as necessary, then go to step 9. If a problem is not found, go to next step.
3. Measure voltage between ground and TP sensor harness connector terminal "C" (Dark Blue wire). While observing voltage, lightly touch and move all related engine wiring harnesses and connectors. Any change in voltage indicates area where a short to voltage may be found. If a problem is found, repair as necessary, then go to step 9. If a problem is not found, go to next step.
4. Turn ignition off and wait 30 seconds. Measure resistance between ground and TP sensor harness connector terminal "B" (Black wire). While observing resistance, lightly touch and move all related engine wiring harnesses and connectors. Any change in resistance indicates area where an open or high resistance may be found. If a problem is found, repair as necessary, then go to step 9. If a problem is not found, go to next step.
5. Inspect TP sensor harness connector for poor connections. Repair connector as necessary, then go to step 9. If connector is okay, go to next step.
6. Inspect PCM harness connectors for poor connections. Repair connector(s) as necessary, then go to step 9. If connectors are okay, go to next step.
7. Connect a jumper wire to TP sensor harness connector terminal "A" (Gray wire on Century, Grand Prix, Impala and Monte Carlo; Gray/Black wire on Alero, Grand Am and Malibu). Connect a second jumper wire to TP sensor harness connector terminal "C" (Dark Blue wire). Connect a DVOM with a "min/max" function to jumper wires. Set DVOM to 40 K/ohms scale. Ensure DVOM and jumper wire connections are good. Press MIN/MAX button on DVOM. Slowly depress accelerator pedal to wide open throttle and back to closed throttle position several times. Press MIN/MAX button, and record MAX reading. Press MIN/MAX button again, and record MIN reading. Repeat this procedure with jumper wire moved from TP sensor harness connector terminal "A" (Gray wire on Century, Grand Prix, Impala and Monte Carlo; Gray/Black wire on Alero, Grand Am and Malibu) to TP sensor harness connector terminal "B" (Black wire). If a MAX value of OL or a MIN value of zero ohms was recorded, go to next step. If a MAX value of OL or a MIN value of zero ohms was not recorded, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
8. Replace TP sensor. After repairs, go to next step.
9. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
10. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Throttle Position (TP) sensor is used by PCM to determine throttle plate angle for various engine management systems. TP sensor is a potentiometer type sensor with 3 circuits: a 5-volt reference circuit, a low reference circuit, and a signal circuit. Rotation of TP sensor rotor from closed throttle position to wide open throttle position provides PCM with a signal voltage from less than one volt to more than 4 volts through TP sensor signal circuit.

PCM will run diagnostic for this DTC when ignition is on. DTC will set when TP sensor intermittently indicates a TP sensor signal voltage of less than .95 volt for .5 second.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain diagnostic system check, go to next step.
2. Turn ignition off. Disconnect TP sensor harness connector. (Scheme 10), (Scheme 14) or (Scheme 16). Turn ignition on. Measure voltage between ground and TP sensor harness connector terminal "A" (Gray wire on Century, Grand Prix, Impala and Monte Carlo; Gray/Black wire on Alero, Grand Am and Malibu). While observing voltage, lightly touch and move all related engine wiring harnesses and connectors for all 5-volt reference circuits. See WIRING DIAGRAMS article. Any change in voltage indicates area where a circuit fault may be found. If a problem is found, repair as necessary, then go to step 8. If a problem is not found, go to next step.
3. Turn ignition off. Reconnect TP sensor harness connector. Turn ignition on. Using scan tool, observe TP sensor voltage parameter. Lightly touch and move related engine wiring harnesses and connectors for TP sensor signal circuit. Any change in voltage indicates area where circuit fault may be found. If a problem is found, repair as necessary, then go to step 8. If a problem is not found, go to next step.
4. Inspect TP sensor harness connector for poor connections. Repair connector as necessary, then go to step 8. If connector is okay, go to next step.
5. Inspect PCM harness connectors for poor connections. Repair connector(s) as necessary, then go to step 8. If connectors are okay, go to next step.
6. Connect a jumper wire to TP sensor harness connector terminal "A" (Gray wire on Century, Grand Prix, Impala and Monte Carlo; Gray/Black wire on Alero, Grand Am and Malibu). Connect a second jumper wire to TP sensor harness connector terminal "C" (Dark Blue wire). Connect a DVOM with a "min/max" function to jumper wires. Set DVOM to 40 k/ohms scale. Ensure DVOM and jumper wire connections are good. Press MIN/MAX button on DVOM. Slowly depress accelerator pedal to wide open throttle and back to closed throttle position several times. Press MIN/MAX button, and record MAX reading. Press MIN/MAX button again, and record MIN reading. Repeat this procedure with jumper wire moved from TP sensor harness connector terminal "A" (Gray wire on Century, Grand Prix, Impala and Monte Carlo; Gray/Black wire on Alero, Grand Am and Malibu) to TP sensor harness connector terminal "B" (Black wire). If a MAX value of OL or a MIN value of zero ohms was recorded, go to next step. If a MAX value of OL or a MIN value of zero ohms was not recorded, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
7. Replace TP sensor. After repairs, go to next step.
8. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
9. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

PCM monitors Heated Oxygen Sensor (HO2S) activity for 100 seconds. PCM determines if HO2S 1 is functioning properly by counting number of HO2S 1 Lean/Rich (L/R) and Rich/Lean (R/L) switches. A L/R switch is determined when HO2S voltage changes from less than 300 mV to more than 600 mV. A R/L switch is determined when HO2S voltage changes from more than 600 mV to less than 300 mV. If PCM determines that HO2S 1 did not switch enough times, DTC P1133 will set.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0101, P0102, P0103, P0106, P0107, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449 or P1441 are not set.
2. System voltage is more than 9 volts.
3. Engine is running in closed loop.
4. Engine is running for at least 3.3 minutes.
5. Engine Coolant Temperature (ECT) is more than 158°F (70°C).
6. TP sensor angle is more than 2 percent.
7. Engine speed is 1300-3000 RPM.
8. Mass airflow is 13-29 grams per second.
9. Above conditions are stable for 3 seconds.

DTC will set when PCM monitors fewer than 25 rich-to-lean and 25 lean-to-rich switches for HO2S 1 during a 100-second monitoring period.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, clear DTCs. Reset fuel trim values. Start engine and let it idle until normal operating temperature is reached. Using scan tool, read HO2S 1 voltage. If HO2S 1 voltage remains at 300-600 mV, go to step 4. If HO2S 1 voltage does not remain at 300-600 mV, go to next step.
3. Condition that set this DTC is not present. This DTC may have been set by one of the following conditions: HO2S 1 connector water intrusion. An intermittently open HO2S 1 high signal circuit. An intermittently open HO2S 1 low reference circuit. An HO2S 1 low reference circuit with high resistance to ground. PCM ground circuits with high resistance. Faulty HO2S 1 or PCM connector terminal contact. An exhaust system leak, typically within 12" up-stream of HO2S 1. A defective HO2S 1. If a problem is found, repair as necessary, then go to step 11. If a problem is not found, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect HO2S 1 harness connector. Connect a fused jumper wire between ground and HO2S 1 harness connector terminal "A". See «HO2S 1 CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table. Connect a second fused jumper wire between ground and HO2S 1 harness connector terminal "B". Turn ignition on. Using scan tool, read HO2S 1 voltage. If scan tool displays less than 20 mV, go to step 8. If scan tool does not display less than 20 mV, go to next step.
5. Turn ignition off. Remove jumper wires. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Measure resistance of signal circuit between HO2S 1 harness connector terminal "B" and PCM harness connector C2 terminal No. 10. (Scheme 5)or (Scheme 6). Also, measure resistance of low reference circuit between HO2S 1 harness connector terminal "A" and PCM harness connector C1 terminal No. 12. If resistance is less than 5 ohms both circuits, go to next step. If resistance is not less than 5 ohms both circuits, go to step 7.
6. Check for correct PCM harness connector terminal contact. If a problem is found, repair as necessary, then go to step 11. If a problem is not found, go to step 10.
7. Repair open or high resistance in appropriate circuit. Probable causes of condition include the following: Poor HO2S connector terminal contact Open or high resistance in sensor harness low reference circuit. This requires HO2S replacement. Poor PCM ground connection. High PCM ground circuit resistance. An ungrounded exhaust system. After repairs, go to step 11.
8. Check for exhaust leaks upstream of HO2S 1. Leak may be very small and typically will be within 12" of HO2S 1. Repair exhaust system as necessary, then go to step 11. If exhaust system is okay, go to next step.
9. Replace HO2S 1. After repairs, go to step 11.
10. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
11. Check for faulty connections at HO2S harness connector. Repair as necessary. After repairs, go to step. If connections are okay, go to next step.
12. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2. If DTC does not reset, go to next step.
13. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

HO2S 1 CIRCUIT IDENTIFICATION

PCM reads Heated Oxygen Sensor (HO2S) activity for 100 seconds. During this period, PCM counts the number of Lean/Rich (L/R) and Rich/Lean (R/L) switches.

With this information, an average time for all transitions can be determined. PCM then divides R/L average by L/R rich average to obtain a ratio. If HO2S ratio is not within range, this DTC will set, indicating that oxygen sensor is not responding as expected to changes in exhaust oxygen content.

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0101, P0102, P0103, P0106, P0107, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449 or P1441 are not set.
2. System voltage is more than 9 volts.
3. Engine is running in closed loop.
4. Engine has been running for at least 60 seconds.
5. Engine Coolant Temperature (ECT) is more than 122°F (50°C).
6. TP sensor angle is more than 2 percent.
7. Engine speed is 1300-3000 RPM.
8. Mass airflow is 13-29 grams per second.

DTC will set when the ratio of averages is not between 4.2 and 0.4 during the 100-second monitoring period.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) . After performing powertrain diagnostic system check, go to next step.
2. If any other DTCs are set, diagnose those DTCs first. If no other DTCs are set, warm engine to normal operating temperature. Operate vehicle within conditions required to set DTC. Using scan tool, read specific DTC information for DTC P1134 until DTC P1134 test runs. If DTC P1134 resets, go to next step. If DTC P1134 does not reset, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
3. Check for exhaust leaks or damaged wiring. Inspect HO2S 1 for proper installation. If a problem is found, repair as necessary, then go to step 11 . If a problem is not found, go to next step.
4. Check for corrosion on HO2S 1 harness connector terminals. Also, check for proper terminal tension at PCM and HO2S 1 harness connectors. If a problem is found, go to step 8 . If a problem is not found, go to next step.
5. Disconnect HO2S 1 harness connector. Connect a fused jumper wire between ground and HO2S 1 harness connector terminal "A". See «HO2S 1 CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table under DTC P1133: HO2S INSUFFICIENT SWITCHING - SENSOR 1. Turn ignition on. Using scan tool, observe HO2S 1 voltage. If voltage is about 450 mV, go to next step. If voltage is not about 450 mV, go to step 9 .
6. Connect a second fused jumper wire between ground and HO2S 1 harness connector terminal "B" (Purple wire). Using scan tool, read HO2S 1 voltage. If voltage is less than 300 mV, go to next step. If voltage is not less than 300 mV, go to step 10 .
7. Replace HO2S 1. After repairs, go to step 11 .
8. Repair connectors as necessary. After repairs, go to step 11 .
9. Repair open in low reference circuit or short to ground in signal circuit. After repairs, go to step 11 .
10. Repair open in signal circuit or poor connections at PCM. After repairs, go to next step.
11. Using scan tool, clear DTCs. Turn ignition off and wait 30 seconds. Start engine and operate vehicle as close to conditions previously recorded in FREEZE FRAME as possible. If DTC resets, go to step 2 . If DTC does not reset, go to next step.
12. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs, system is okay.

The Crankshaft Position Sensor (CKP) system variation learning feature is used to calculate reference period errors caused by slight tolerance variations in the crankshaft, the crankshaft balancer interrupter rings, and the crankshaft position sensor Hall Effect switches. The calculated error allows PCM to accurately compensate for reference period variations. The crankshaft position system variation learning feature enhances the ability of the PCM to detect misfire events over a wider range of engine speed and load.

The crankshaft position system variation values are stored in the PCM non-volatile memory after the crankshaft position system variation learn procedure has been performed. DTC P1336 indicates that the crankshaft position system variation values have not been stored in the PCM, and the crankshaft position system variation learn procedure must be performed. The learn procedure is required after 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 repair(s) which disturbs crankshaft/harmonic balancer to crankshaft position sensor relationship.

PCM will run diagnostic for this DTC when DTC P0336, P0341 or P1374 are not set and engine coolant temperature is more than 156°F (69°C). DTC will set when crankshaft position system variation values are not stored in PCM memory.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) . 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»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__crankshaft-position-sensor-system-variation-learn) under PROGRAMMING.

The crankshaft position system variation compensating values are stored in the PCM's non-volatile memory after a learn procedure has been performed. If actual crankshaft position variation is not within the crankshaft position system variation compensating values stored in the PCM, this DTC may set.

If the crankshaft position system variation learn procedure cannot be performed successfully, check the following conditions and correct as necessary

1. ECT less than 158°F (70°C).
2. Allow engine to warm-up to greater than 158°F (70°C).
3. PCM related DTC(s) set.
4. Scan tool crankshaft position system variation learn function will be disabled of any PCM DTCs other than DTC P1336 are stored.
5. Camshaft position signal problem detected.
6. 3X reference signal problem detected.
7. 24X reference signal problem detected.

The Ignition Control (IC) module sends signals that PCM requires for fuel control and spark advance calculations. At start of engine crank, IC module controls spark advance (by-pass mode). When the second 3X reference pulse is recognized by the PCM, PCM applies 5 volts to by-pass circuit, commanding IC module to switch spark advance to PCM control (IC mode). If PCM detects an open in the IC circuit, DTC P1351 will set. Engine will start and may run in by-pass mode timing.

PCM will run diagnostic for this DTC when engine speed is more than 600 RPM. DTC will set when PCM detects an open in IC circuit for 100 crankshaft revolutions.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within conditions noted in FREEZE FRAME/FAILURE RECORDS data. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed this ignition cycle, go to «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
3. Turn ignition off. Disconnect PCM harness connector. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Turn ignition on. Measure resistance between PCM harness connector C1 terminals No. 48 (Red/Black wire) and No. 54 (White wire). (Scheme 5)or (Scheme 6). If resistance is less than 500 ohms, go to step 5. If resistance is not less 500 ohms, go to next step.
4. Turn ignition off. Disconnect IC module harness connector located on top of engine, at rear of engine compartment. Check for open in IC timing control circuit (White wire) between PCM harness connector C1 terminal No. 54 and IC module harness connector C1 terminal "B". (Scheme 24) Repair circuit as necessary, then go to step 9. If circuit is okay, go to step 6.
5. Check for poor terminal connections at PCM. Repair as necessary. After repairs, go to step 9. If connections are okay, go to step 8.
6. Check for poor terminal connections at IC module. Repair as necessary. After repairs, go to step 9. If connections are okay, go to next step.
7. Replace IC module. After replacing module, go to step 9.
8. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
9. Read and record FAILURE RECORDS data for this DTC. Clear DTCs. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool indicates that this DTC FAILED THIS IGN, return to step 2. If scan tool does not indicate that this DTC FAILED THIS IGN, go to next step.
10. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Scheme 24

Engine will start and run with IC module controlling spark timing. If condition is intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

The Ignition Control (IC) module has independent power and ground circuits. The circuits between the IC module and the PCM consist of the following: IC timing signal circuit, IC timing control circuit, low-resolution engine speed signal circuit and low reference signal circuit.

The IC module sends 3x signals to the PCM. The IC module controls the timing advance during engine cranking. When the second 3X reference pulse is recognized by the PCM, the PCM applies 5 volts to the IC signal circuit, commanding the IC module to switch spark advance to PCM control (IC mode).

PCM will run diagnostic for this DTC when engine is running. DTC will set when PCM detects an open in IC timing signal circuit. Condition must be present for 106 crankshaft revolutions.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within conditions noted in FREEZE FRAME/FAILURE RECORDS data. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed this ignition cycle, go to «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
3. Turn ignition off. Disconnect PCM harness connector. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Turn ignition on. Connect a test light between battery positive and PCM harness connector C1 terminal No. 48 (Red/Black wire). (Scheme 5)or (Scheme 6). If test light illuminates, go to step 6. If test light does not illuminate, go to next step.
4. Turn ignition off. Check for open in low reference circuit (Red/Black wire) between PCM harness connector C1 terminal No. 48 and IC module harness connector C1 terminal "F". (Scheme 24) IC module is located on top of engine, at rear of engine compartment. Repair circuit as necessary, then go to step 9. If circuit is okay, go to next step.
5. Check for poor terminal connections at IC modules. Repair connector as necessary, then go to step 9. If connections are okay, go to step 7.
6. Turn ignition off. Measure resistance between PCM harness connector C1 terminals No. 48 (Red/Black wire) and No. 54 (White wire). Turn ignition on. Connect a test light between battery positive and PCM harness connector C1 terminal No. 53 (Tan/Black wire). If resistance is more than 5000 ohms, go to step 8. If resistance is not more than 5000 ohms, go to next step.
7. Turn ignition off. Check for open in IC timing signal circuit (Tan/Black wire) between PCM harness connector C1 terminal No. 53 and IC module harness connector C1 terminal "A". (Scheme 24) Repair circuit as necessary, then go to step 12. If circuit is okay, go to step ' 9.
8. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step 12. If connector is okay, go to step 11.
9. Inspect IC module harness connector for poor connections. Repair connector as necessary, then go to step 12. If connector is okay, go to next step.
10. Replace IC module. After repairs, go to step 12.
11. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
12. Read and record FAILURE RECORDS data for this DTC. Clear DTCs. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool indicates that this DTC FAILED THIS IGN, return to step 2. If scan tool does not indicate that this DTC FAILED THIS IGN, go to next step.
13. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

Engine will start and run with IC module controlling spark timing. If condition is intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

The Ignition Control Module (IC) module has independent power and ground circuits. The circuits between the IC module and the PCM consist of the following: IC timing signal circuit, IC timing control circuit, low-resolution engine speed signal circuit and low reference signal circuit.

The IC module sends 3x signals to the PCM. The IC module controls the timing advance during engine cranking. When the second 3X reference pulse is recognized by the PCM, the PCM applies 5 volts to the IC signal circuit, commanding the IC module to switch spark advance to PCM control (IC mode).

PCM will run diagnostic for this DTC under the following conditions

1. Engine speed is more than 600 RPM.
2. DTC P1351 is not set.

DTC will set when PCM does not monitor IC pulses while IC mode spark advance is commanded. Condition must be present for 100 crankshaft revolutions.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, monitor DTC information for DTC P1362. If scan tool indicates that DTC P1362 is current, go to step 6. If scan tool does not indicate that DTC P1362 is current, go to next step.
3. Using scan tool, observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle under conditions required to set DTC. If DTC P1361 fails this ignition cycle, go to next step. If DTC P1361 does not fail this ignition cycle, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Turn ignition on. Connect a test light between ground and PCM harness connector C1 terminal No. 54 (White wire). (Scheme 5)or (Scheme 6). If test light illuminates, go to next step. If test light does not illuminate, go to step 14.
5. Turn ignition off. Disconnect IC module harness connector C1. Turn ignition on. Connect a test light between ground and PCM harness connector C1 terminal No. 54 (White wire). If test light illuminates, go to step 10. If test light does not illuminate, go to step 13.
6. Turn ignition off. Disconnect IC module and PCM harness connectors. Connect a test light between battery positive and PCM harness connector C1 terminal No. 54 (White wire). If test light illuminates, go to step 11. If test light does not illuminate, go to next step.
7. Connect test light between battery positive and PCM harness connector C1 terminal No. 53 (Tan/Black wire). If test light illuminates, go to step 12. If test light does not illuminate, go to next step.
8. Check for short between IC timing control circuit (White wire) and IC timing signal circuit (Tan/Black wire). Repair circuits as necessary, then go to step 15. If circuits are okay, go to next step.
9. Reconnect IC module connector C1. Turn ignition on. Measure resistance between ground and PCM harness connector C1 terminal No. 54 (White wire). While observing resistance, probe PCM harness connector C1 terminal No. 53 (Tan/Black wire) with a test light connected to battery positive. If resistance toggles between 100-600 ohms and 6000-10,000 ohms, go to step 14. If resistance does not toggle between 100-600 ohms and 6000-10,000 ohms, go to step 13.
10. Repair short to voltage in IC timing control circuit. After repairs, go to step 15.
11. Repair short to low reference circuit or short to ground in IC timing control circuit. After repairs, go to step 15.
12. Repair short to low reference circuit or short to ground in IC timing signal circuit. After repairs, go to step 15.
13. Replace IC module. After replacing IC module, go to step 15.
14. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
15. Read and record FAILURE RECORDS data for this DTC. Clear DTCs. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool indicates that this DTC FAILED THIS IGN, return to step 2. If scan tool does not indicate that this DTC FAILED THIS IGN, go to next step.
16. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

The Ignition Control (IC) module has independent power and ground circuits. The circuits between the IC module and the PCM consist of the following: IC timing signal circuit, IC timing control circuit, low-resolution engine speed signal circuit and low reference signal circuit.

The IC module sends 3x signals to the PCM. The IC module controls the timing advance during engine cranking. When the second 3X reference pulse is recognized by the PCM, the PCM applies 5 volts to the IC signal circuit, commanding the IC module to switch spark advance to PCM control (IC mode).

PCM will run diagnostic for this DTC when engine is running. DTC will set when PCM detects a short to voltage in IC timing signal circuit. Condition must be present for 100 crankshaft revolutions.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, monitor DTC information for DTC P1361. If scan tool indicates that DTC P1361 is current, go to step 6. If scan tool does not indicate that DTC P1361 is current, go to next step.
3. Using scan tool, observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle under conditions required to set DTC. If DTC P1362 fails this ignition cycle, go to next step. If DTC P1362 does not fail this ignition cycle, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Turn ignition on. Connect a test light between ground and PCM harness connector C1 terminal No. 53 (Tan/Black wire). (Scheme 5)or (Scheme 6). If test light illuminates, go to next step. If test light does not illuminate, go to step 14.
5. Turn ignition off. Disconnect IC module harness connector C1. Turn ignition on. Connect a test light between ground and PCM harness connector C1 terminal No. 53 (Tan/Black wire). If test light illuminates, go to step 10. If test light does not illuminate, go to step 13.
6. Turn ignition off. Disconnect IC module and PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Connect a test light between battery positive and PCM harness connector C1 terminal No. 54 (White wire). (Scheme 5)or (Scheme 6). If test light illuminates, go to step 11. If test light does not illuminate, go to next step.
7. Connect a test light between ground and PCM harness connector C1 terminal No. 53 (Tan/Black wire). If test light illuminates, go to step 12. If test light does not illuminate, go to next step.
8. Turn ignition off. Check for short between IC timing control circuit (White wire) and IC timing signal circuit (Tan/Black wire). Repair circuits as necessary, then go to step 15. If circuits are okay, go to next step.
9. Reconnect IC module connector C1. Turn ignition on. Measure resistance between ground and PCM harness connector C1 terminal No. 54 (White wire). While observing resistance, probe PCM harness connector C1 terminal No. 53 (Tan/Black wire) with a test light connected to battery positive. If resistance toggles between 100-600 ohms and 6000-10,000 ohms, go to step 14. If resistance does not toggle between 100-600 ohms and 6000-10,000 ohms, go to step 13.
10. Repair short to voltage in IC timing control circuit. After repairs, go to step 15.
11. Repair short to ground in IC timing control circuit. After repairs, go to step 15.
12. Repair short to ground in IC timing signal circuit. After repairs, go to step 15.
13. Replace IC module. After replacing IC module, go to step 15.
14. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
15. Read and record FAILURE RECORDS data for this DTC. Clear DTCs. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool indicates that this DTC FAILED THIS IGN, return to step 2. If scan tool does not indicate that this DTC FAILED THIS IGN, go to next step.
16. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

The 3X reference signal is produced by the Ignition Control (IC) module. The IC module calculates the 3X reference signal by dividing the Crankshaft Position (CKP) sensor 7X pulses by 2 when the engine is running and the CKP synchronizing pulses are being received. The PCM uses the 3X reference signal to calculate the engine RPM and the CKP at engine speeds above 1450-1750 RPM. The PCM also uses these pulses to initiate injector pulses. The PCM compares the 3X reference pulses to the 24X CKP pulses and the Camshaft Position (CMP) sensor pulses. If the PCM receives an incorrect number of pulses on the 3X circuit, a DTC P1374 will set, and the PCM will use the 24X CKP reference circuit for fuel and ignition control. The engine will continue to start and run using only the 24X CKP and CMP sensor signals.

PCM will run diagnostic for this DTC when engine is running and 24X pulses are being received. DTC will set when

1. The ratio of 24X reference pulses to 3X reference pulses received by the PCM does not equal 8.
2. The ratio of 24X reference pulses to CMP PCM input pulses received by the PCM equals 48.
3. The conditions are present for more than 10 seconds.

Diagnostic Procedure (Except Grand Prix)

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain 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, see appropriate BASIC DIAGNOSTIC PROCEDURES article.
3. Using scan tool, observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Operate vehicle within conditions noted in FREEZE FRAME/FAILURE RECORDS data. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed this ignition cycle, go to «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
4. Turn ignition off. Install Injector Harness Load Tester (J-34730-380) to multi-way injector harness connector. Disconnect IC module harness connector C1. Turn ignition on. Using a test light connected to battery positive, repeatedly probe IC module harness connector C1 terminal "E" (Purple/White wire) while observing injector harness load tester light. (Scheme 24) If injector harness load tester light flashes, go to step 8. If injector harness load tester light does not flash, go to next step.
5. Turn ignition off. Disconnect PCM harness connector. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Turn ignition on. Check for open or short in low resolution engine speed signal circuit (Purple/White wire) between IC module harness connector C1 terminal "E" and PCM harness connector C1 terminal No. 8. (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 11. If circuit is okay, go to next step.
6. Check for faulty low resolution engine speed signal circuit connection at PCM. If connection is faulty, repair as necessary. After repairs, go to step 11. If connection is okay, go to next step.
7. Check for incorrect harness routing near secondary ignition components, ignition coil arcing to wiring harness or IC module. Check ignition coils for cracks, carbon tracking or other signs of damage. Check for secondary ignition wire(s) arcing to wiring harness. If a problem is found, repair as necessary. After repairs, go to step 11. If no problem is found, go to step 10.
8. Check for faulty connections at IC module. If faulty connection is found, repair as necessary. After repairs, go to step 11. If connections are okay, go to next step.
9. Replace IC module. After replacing IC module, go to step 11.
10. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
11. Read and record FAILURE RECORDS data for this DTC. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool indicates that this DTC FAILED THIS IGN, return to step 2. If scan tool does not indicate that this DTC FAILED THIS IGN, go to next step.
12. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain diagnostic system check, go to next step.
2. Start engine. Allow engine to idle for 2 minutes. Using scan tool, observe DTC information. If scan tool indicates that this DTC failed this ignition cycle, go to step 4. If scan tool does not indicate that this DTC failed this ignition cycle, go to next step.
3. Using scan tool, observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Operate vehicle within conditions noted in FREEZE FRAME/FAILURE RECORDS data. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed this ignition cycle, go to «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
4. Turn ignition off. Disconnect IC module harness connector C1. Remove INJ fuse (10-amp) from underhood fuse block. Turn ignition on. While observing engine speed parameter on scan tool, momentarily connect a test light between battery positive and IC module harness connector C1 terminal "E" (Purple/White wire). If scan tool displays an engine speed, go to step 8. If scan tool does not display an engine speed, go to next step.
5. If test light illuminated, go to step 7. If test light did not illuminate, go to next step.
6. Turn ignition off. Disconnect PCM harness connectors. (Scheme 3) Turn ignition on. Check for open or short to voltage in low resolution engine speed signal circuit (Purple/White wire) between IC module harness connector C1 terminal "E" and PCM harness connector C1 terminal No. 8. (Scheme 6) Repair circuit as necessary, then go to step 12. If circuit is okay, go to step 9.
7. Turn ignition off. Disconnect PCM harness connectors. (Scheme 3) Check for short to ground in low resolution engine speed signal circuit (Purple/White wire) between IC module harness connector C1 terminal "E" and PCM harness connector C1 terminal No. 8. (Scheme 6) Repair circuit as necessary, then go to step 12. If circuit is okay, go to step 9.
8. Check for faulty connections at IC module. If faulty connection is found, repair as necessary. After repairs, go to step 12. If connections are okay, go to step 10.
9. Check for faulty connections at PCM. If faulty connection is found, repair as necessary. After repairs, go to step 12. If connections are okay, go to step 11.
10. Replace IC module. After replacing IC module, go to step 12.
11. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
12. Read and record FAILURE RECORDS data for this DTC. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool indicates that this DTC FAILED THIS IGN, return to step 2. If scan tool does not indicate that this DTC FAILED THIS IGN, go to next step.
13. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

DTC P1374 can be caused by secondary components leaking high voltage into the IC module. Check for incorrect harness routing near secondary ignition components. Inspect ignition coils for arcing to wiring harness or IC module. Inspect ignition coils for cracks, carbon tracking or other signs of damage. Check secondary ignition wires for arcing to wiring harness. If DTC is determined to be intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

PCM receives rough road information from Electronic Brake Control Module (EBCM)/Electronic Brake Traction Control Module (EBTCM) on the serial data circuit. PCM uses this information to enhance the misfire diagnostic by distinguishing crankshaft speed variations caused by driving on rough road surfaces from variations caused by true misfires. EBCM/EBTCM transmits rough road information based on inputs from wheel speed sensors. If EBCM/EBTCM detects a condition which will allow it to properly identify rough road situations while a misfire condition is being detected by the PCM, DTC P1380 will set.

PCM will run diagnostic for this DTC under the following conditions: engine load is less than 87 percent, engine speed is less than 5000 RPM, vehicle speed is greater than 10 MPH, misfire DTC is occurring and requesting MIL to be illuminated. DTC will set when PCM has detected an EBCM/EBTCM rough road sensing error.

Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK . After performing powertrain diagnostic system check, diagnose ABS/TCS system. See appropriate ANTI-LOCK article in BRAKES.

If this DTC is set, it indicates that the anti-lock brake/traction control system has detected a malfunction which will not allow the EBCM/EBTCM to transmit correct rough road data to PCM. Diagnose ABS system. See appropriate ANTI-LOCK article in BRAKES.

PCM uses rough road information to enhance misfire diagnostic by distinguishing crankshaft speed variations caused by driving on rough rod surfaces from variations caused by true misfires. The Electronic Brake Control Module (EBCM)/Electronic Brake Traction Control Module (EBTCM) transmits rough road information based on inputs from the wheel speed sensors. If a loss of communication occurs which causes the PCM not to receive rough road information while DTC P0300 is requesting MIL, DTC P1381 will set.

PCM will run diagnostic for this DTC under the following conditions

1. Engine load is less than 87 percent.
2. Engine speed is less than 5000 RPM.
3. Vehicle speed is more than 10 MPH.
4. A misfire DTC is occurring and is requesting MIL to be illuminated.

DTC will set when PCM is detecting a loss of communication with EBCM/EBTCM for at least 5 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) . After performing powertrain diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, attempt to display ABS data. If ABS data can be displayed, go to next step. If ABS data cannot be displayed, go to step 4 .
3. Check serial data circuit for an open or poor connection between PCM and EBCM/EBTCM. Repair as necessary. After repairs, go to step 7 . If circuit is okay, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
4. Turn ignition off. Disconnect EBCM/EBTCM located in left rear of engine compartment. Turn ignition on. Measure voltage between ground and serial data circuit terminal at EBCM/EBTCM connector. If voltage reading is 1-5 volts, go to next step. If voltage reading is not 1-5 volts, go to step 6 .
5. Check for poor terminal connections at EBCM/EBTCM connector. Repair as necessary. After repairs, go to step 7 . If connections are okay, go to next step.
6. Check for an open or short to ground in serial data circuit. Repair as necessary. After repair is completed, go to next step. If circuit is okay, check ABS system. See appropriate ANTI-LOCK article in BRAKES.
7. Turn ignition on. Using scan tool, attempt to display ABS data. If ABS data can be displayed, go to next step. If ABS data cannot be displayed, go to step 4 .
8. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool indicates that this DTC FAILED THIS IGN, return to step 2 . If scan tool does not indicate that this DTC FAILED THIS IGN, go to next step.
9. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs, system is okay.

Setting of this DTC indicates that a misfire was detected and that the PCM could not determine if fault was a true misfire or due to operating vehicle on a rough surface. A misfire can be a true misfire with or without setting this DTC. Check PCM or Electronic Brake Control Module (EBCM) for poor connections.

PCM monitors EGR valve pintle position input to ensure that valve responds properly to commands from PCM. When ignition is turned on, PCM learns the EGR closed valve pintle position. PCM compares the learned EGR closed valve pintle position to the actual position when EGR valve is commanded closed. If actual EGR position indicates that EGR valve is still open when PCM is commanding EGR closed, DTC P1404 will set.

PCM will run diagnostic for this DTC when system voltage is more than 11 volts. DTC will set when EGR position sensor voltage is .2 volt more than EGR learned minimum position when desired EGR position is commanded to zero percent. Condition must be present twice.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain diagnostic system check, go to next step. NOTE: If DTC P0403 is set, diagnose DTC P0403 first. See «DTC P0403: EGR SOLENOID CONTROL CIRCUIT»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
2. Start engine and let it idle. Using scan tool, observe actual EGR position. If actual EGR position is zero percent, go to next step. If actual EGR position is not zero percent, go to step 5.
3. Turn ignition off then on. Using scan tool, command EGR valve from zero to 100 percent. If desired EGR position remains within 15 percent of actual EGR position at all commanded positions, go to next step. If desired EGR position does not remain within 15 percent of actual EGR position, go to step 6.
4. Using scan tool, review and record FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Operate vehicle within FAILURE RECORDS conditions. Monitor SPECIFIC DTC INFO for this DTC until this DTC test runs. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan does not indicate that this DTC failed this ignition cycle, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l).
5. Turn ignition off. Disconnect EGR valve harness connector. Turn ignition on. Observe actual EGR position on scan tool. If actual EGR position is at zero percent, go to next step. If actual EGR position is not at zero percent, go to step 9.
6. Measure voltage between EGR valve harness connector terminals "B" and "D". See «EGR VALVE CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table. (Scheme 23) If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step 8.
7. Connect a fused jumper wire between EGR valve harness connector terminals "C" and "D". See «EGR VALVE CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table. (Scheme 23) If scan tool indicates that EGR position is about 100 percent, go to step 13. If scan tool does not indicate that EGR position is about 100 percent, go to step 11.
8. Measure voltage between ground and EGR valve harness connector terminal "D". If voltage is about 5 volts, go to step 10. If voltage is not about 5 volts, go to step 12.
9. Check for short to voltage in EGR valve position sensor signal circuit between EGR valve harness connector terminal "C" and PCM harness connector C2 terminal No. 28. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 17. If circuit is okay, go to step 14.
10. Check for open or high resistance in EGR valve position sensor low reference circuit (Black wire) between EGR valve harness connector terminal "B" and PCM harness connector C1 terminal No. 31. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 17. If circuit is okay, go to step 14.
11. Check for high resistance or high resistance short to ground in EGR valve position sensor signal circuit between EGR valve harness connector terminal "C" and PCM harness connector C2 terminal No. 28. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 17. If circuit is okay, go to step 14.
12. Check for open, short to ground or short to voltage in 5-volt reference circuit between EGR valve harness connector terminal "D" and PCM harness connector C2 terminal No. 30. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 17. If circuit is okay, go to step 14.
13. Inspect EGR valve harness connector for poor connections. Repair connector as necessary, then go to step 17. If connector is okay, go to step 15.
14. Inspect PCM harness connectors for poor connections. Repair connectors as necessary, then go to step 17. If connectors are okay, go to step 16.
15. Replace EGR valve. After repairs, go to step 17.
16. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
17. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool indicates that this DTC FAILED THIS IGN, return to step 2. If scan tool does not indicate that this DTC FAILED THIS IGN, go to next step.
18. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, diagnose those DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs, system is okay.

EGR VALVE CIRCUIT IDENTIFICATION

Check for excessive deposits on EGR valve pintle or seat, causing EGR valve to stick. Check for poor connections at EGR and PCM connector. Check for faulty terminal connections or damaged harness. If condition is intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

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

PCM will run diagnostic for this DTC under the following conditions

1. DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0440, P0442, P0443, P0446, P0449, P0452, P0453, P1106, P1107, P1112, P1114, P1115, P1121, or P1122 are not set.
2. Ignition voltage is 10-18 volts.
3. Barometric pressure is more than 75 kPa.
4. Fuel level is 15-85 percent.
5. Engine Coolant Temperature (ECT) and Intake Air Temperature (IAT) are 39-86°F (4-30°C).
6. Start-up ECT and IAT are within 16°F of each other.
7. Vehicle speed is less than 75 MPH.

DTC will set when PCM detects vacuum during a non purge condition.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) . After performing powertrain diagnostic system check, go to next step.
2. Check if DTC P0443, P0449, P0452 or P0453 is also set. If any of these DTCs are set, diagnose affected DTC first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If DTC P0443, P0449, P0452 or P0453 is not set, go to next step.
3. Remove fuel filler cap. Turn ignition on. Using scan tool, monitor Fuel Tank Pressure (FTP). If scan tool indicates that FTP is -.5 to +.5 in. H2O, go to next step. If scan tool does not indicate that FTP is -.5 to +.5 in. H2O, go to «DTC P0453: FUEL TANK PRESSURE SENSOR CIRCUIT - HIGH VOLTAGE»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) .
4. Disconnect EVAP purge pipe from EVAP canister purge valve. Connect a vacuum gauge to EVAP purge port. Disconnect EVAP canister purge valve harness connector. Start engine. While monitoring vacuum gauge, increase engine speed to 1200-1500 RPM. If vacuum increases, go to next step. If vacuum does not increase, go to «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) .
5. Replace EVAP canister purge valve. After repairs, go to next step.
6. Using scan tool, monitor FTP. Start engine and let it idle for 30 seconds. If scan tool indicates that FTP is -.5 to +.5 in. H2O, go to next step. If scan tool does not indicate that FTP is -.5 to +.5 in. H2O, go to step 3 .
7. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, go to perform appropriate test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs that have not been diagnosed, system is okay.

EVAP system tests run when engine is first started and meets conditions described in CODE ENABLE CRITERIA. An intermittent condition could be caused by an improperly installed or damaged EVAP canister purge valve, or by a temporary blockage in the EVAP canister purge valve.

Ignition voltage is supplied directly to A/C compressor clutch relay. PCM controls the relay by grounding the control circuit via an internal solid state device called a driver. If PCM senses a voltage on this circuit other than what is expected, this DTC will set.

PCM will run diagnostic for this DTC when ignition voltage is 9-18 volts, engine speed is more than 80 RPM and PCM driver is activated. DTC will set when PCM detects an improper voltage level on control circuit for at least 30 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain diagnostic system check, go to next step. NOTE: Before proceeding, ensure ambient air temperature is more than 38°F (3°C).
2. Turn ignition off. Inspect A/C compressor for free rotation. Start engine. Turn Heating, Ventilation and Air Conditioning (HVAC) system off. If A/C compressor operates, diagnose A/C system. See appropriate article in AIR CONDITIONING & HEATING. If A/C compressor does not operate, go to next step.
3. Turn ignition off then on. Using scan tool, command A/C clutch relay on and off. If A/C clutch relay turns on and off with each command, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM. If A/C clutch relay does not turn on and off with each command, go to next step.
4. Turn ignition off. Remove A/C clutch relay from underhood fuse block. Turn ignition on. Connect a test light between ground and battery positive voltage circuit cavity for A/C clutch relay in underhood fuse block. If test light illuminates, go to next step. If test light does not illuminate, go to step 11.
5. Connect test light between battery positive voltage circuit cavity and A/C clutch relay control circuit cavity in underhood fuse block. Using scan tool, command A/C clutch relay 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.
6. If test light remains illuminated with each command, go to step 8. If test light does not remain illuminated with each command, go to next step.
7. Check for open or short to voltage in A/C clutch relay control circuit (Dark Green/White wire) between A/C clutch relay and PCM harness connector C2 terminal No. 39. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 14. If circuit is okay, go to step 10.
8. Check for short to ground in A/C clutch relay control circuit (Dark Green/White wire) between A/C clutch relay and PCM harness connector C2 terminal No. 39. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). (Scheme 5)or (Scheme 6). Repair circuit as necessary, then go to step 14. If circuit is okay, go to step 10.
9. Check for poor connections at A/C clutch relay. Repair connector as necessary, then go to step 14. If connector is okay, go to step 12.
10. Check for poor connections at PCM. Repair connector as necessary, then go to step 14. If connector is okay, go to step 13.
11. Repair battery positive voltage circuit. See WIRING DIAGRAMS article. After repairs, go to step 14.
12. Replace A/C clutch relay. After replacing relay, go to step 14.
13. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
14. Using scan tool, clear DTCs. Operate vehicle within FAIL RECORDS data. Recheck DTC. If DTC resets, go to step 3. If DTC does not reset, system is okay.

If problem is intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

The PCM uses the 5-volt reference 1 circuit as a sensor feed TP sensor, MAP sensor, EGR valve position sensor and Fuel Tank Pressure (FTP) sensor. PCM monitors the voltage on the 5-volt reference 1 circuit. If the voltage is out of tolerance, the PCM will set DTC P1635.

PCM will run diagnostic for this DTC when engine is running. DTC will set when PCM detects a voltage out of range/tolerance on the 5-volt reference 1 circuit and condition is present longer than 10 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check). After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within conditions required to set DTC. If this DTC fails this ignition cycle, go to next step. If this DTC does not fail this ignition cycle, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
3. Visually and physically inspect PCM grounds and engine grounds. See WIRING DIAGRAMS article. Ensure grounds are clean and tight. If a problem is found, repair as necessary, then go to step 13. If a problem is not found, go to next step.
4. Turn ignition off. Disconnect EGR valve harness connector. Turn ignition on. Measure voltage between ground and EGR valve harness connector terminal "D". See «EGR VALVE CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table under DTC P1404: EGR CLOSED POSITION PERFORMANCE. (Scheme 23) If voltage is about 5 volts, go to step 6. If voltage is not about 5 volts, go to next step.
5. If voltage is more than 5 volts, go to step 9. If voltage is not more than 5 volts, go to step 7.
6. Reconnect EGR valve. Disconnect TP sensor harness connector. Measure voltage between ground and TP sensor harness connector terminal "A" (Gray wire on Century, Grand Prix, Impala and Monte Carlo; Gray/Black wire on Alero, Grand Am and Malibu). If voltage is about 5 volts, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM. If voltage is not about 5 volts, go to step 10.
7. While observing voltmeter, individually disconnect all other components connected to 5-volt reference 1 circuit. See WIRING DIAGRAMS article. If voltage changes when one of the components is disconnected, replace component that caused voltage to change, then go to step 13. If voltage did not change, go to next step.
8. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Check for short to ground or short to any sensor low reference circuit in 5-volt reference 1 circuit. If a problem is found, repair as necessary, then go to step 13. If a problem is not found, go to step 12.
9. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location). Check for short to voltage in 5-volt reference 1 circuit, MAP sensor signal circuit and FTP sensor signal circuit. If a problem is found, repair as necessary, then go to step 13. If a problem is not found, go to step 12.
10. Check for short between EGR 5-volt reference 1 circuit and EGR solenoid high control circuit. See «EGR VALVE CIRCUIT IDENTIFICATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) table under DTC P1404: EGR CLOSED POSITION PERFORMANCE. If a problem is found, repair as necessary, then go to step 13. If a problem is not found, go to next step.
11. Replace EGR valve. After repairs, go to step 13.
12. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After repair is completed, go to next step.
13. Using scan tool, select CLEAR INFO or CLEAR DTCs function to clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for this DTC until DTC test runs. If scan tool indicates that this DTC FAILED THIS IGN, repeat step 2. If scan tool does not indicate that this DTC FAILED THIS IGN, go to next step.
14. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, go to perform appropriate test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions). If scan tool does not display any DTCs that have not been diagnosed, system is okay.

PCM uses 5-volt reference 2 circuit as a sensor feed for A/C refrigerant pressure sensor. PCM monitors voltage on this circuit. If PCM senses voltage out of tolerance/range, DTC will set.

PCM will run diagnostic for this DTC when engine is running. DTC will set when PCM detects an out of tolerance condition on 5-volt reference 2 circuit and condition is present for longer than 10 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) . After performing powertrain diagnostic system check, go to next step.
2. Using scan tool, observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within conditions required to set DTC. If this DTC fails this ignition cycle, go to next step. If this DTC does not fail this ignition cycle, see «INTERMITTENT TROUBLE CODE DETERMINATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__intermittent-trouble-code-determination) under SELF-DIAGNOSTIC SYSTEM.
3. Visually and physically inspect PCM grounds and engine grounds. See WIRING DIAGRAMS article. Ensure grounds are clean and tight. If a problem is found, repair as necessary, then go to step 12 . If a problem is not found, go to next step.
4. Turn ignition off. Disconnect A/C pressure sensor harness connector located on left side of engine compartment. Turn ignition on. Measure voltage between ground and A/C pressure sensor harness connector terminal "B" (Gray wire). If voltage is about 5 volts, go to step 10 . If voltage is not about 5 volts, go to next step.
5. If voltage is more than 5 volts, go to next step. If voltage is not more than 5 volts, go to step 7 .
6. Turn ignition off. Disconnect PCM harness connectors. See «PCM LOCATION»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__pcm-location) . Check for short to voltage on 5-volt reference 2 circuit. See WIRING DIAGRAMS article. If a problem is found, repair as necessary, then go to step 12 . If a problem is not found, go to step 11 .
7. Turn ignition off. Measure resistance between A/C pressure sensor harness connector terminals "A" (Black wire) and "B" (Gray wire). If resistance is infinite, go to next step. If resistance is not infinite, go to step 9 .
8. Measure resistance between ground and A/C pressure sensor harness connector terminal "B" (Gray wire). If resistance is infinite, go to step 11 . If resistance is not infinite, go to next step.
9. Repair short to ground or short to low reference circuit. See WIRING DIAGRAMS article. After repairs, go to step 12 .
10. Replace A/C pressure sensor. After repairs, go to step 12 .
11. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . After replacing PCM, go to next step.
12. Using scan tool, read and record FAILURE RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, select SPECIFIC DTC INFO for this DTC. If scan tool indicates that this DTC FAILED THIS IGN, return to step 2 . If scan tool does not indicate that this DTC FAILED THIS IGN, go to next step.
13. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, go to perform appropriate test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs that have not been diagnosed, system is okay.

Output Driver Modules (ODM) are chips that are inside the PCM. ODMs provide grounded outputs that control devices. Each output has an internal feedback circuit that connects to the PCM microprocessor. ODM 1 determines if the voltage or the current may cause damage to the PCM. The PCM monitors voltage through the ignition 1 input. Any incorrect current that is on a circuit to the ODM will cause the ODM to report this DTC.

PCM will run diagnostic for this DTC when ignition is on. DTC will set when the ODM has detected a voltage more than 33 volts, or excessive current is detected on any circuit to the ODM. Condition must be present for 30 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) . After performing powertrain diagnostic system check, go to next step.
2. Check if DTC P0560 is set. If DTC P0560 is set, perform ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If DTC P0560 is not set, go to next step.
3. Using scan tool, select OUTPUT DRIVER DATA list. Observe scan tool parameters. If any parameters indicate a fault is present, go to next step. If no parameters indicate a fault is present, go to step 5 .
4. Check for short to voltage on control circuit for component that indicated a fault. Repair circuit as necessary, then go to step 6 . If circuit is okay, go to next step.
5. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . After replacing PCM, go to next step.
6. Using scan tool, clear DTCs. Start engine and let it idle until normal operating temperature is reached. Using scan tool, select SPECIFIC DTC function for this DTC. Operate vehicle under conditions required to set DTC until scan tool indicates that diagnostic ran. If diagnostic passed, go to next step. If diagnostic did not pass, go to step 2 .
7. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, go to perform appropriate test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs that have not been diagnosed, system is okay.

An overcharging condition may set this DTC. Perform ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If problem is intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Output Driver Modules (ODM) are chips that are inside the PCM. ODMs provide grounded outputs that control devices. Each output has an internal feedback circuit that connects to the PCM microprocessor. ODM 2 determines if the voltage or the current may cause damage to the PCM. The PCM monitors voltage through the battery input. Any incorrect current that is on a circuit to the ODM will cause the ODM to report this DTC.

PCM will run diagnostic for this DTC when ignition is on. DTC will set when the ODM has detected a voltage more than 33 volts, or excessive current is detected on any circuit to the ODM. Condition must be present for 30 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) . After performing powertrain diagnostic system check, go to next step.
2. Check if DTC P0560 is set. If DTC P0560 is set, perform ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If DTC P0560 is not set, go to next step.
3. Using scan tool, select OUTPUT DRIVER DATA list. Observe scan tool parameters. If any parameters indicate a fault is present, go to next step. If no parameters indicate a fault is present, go to step 5 .
4. Check for short to voltage on control circuit for component that indicated a fault. Repair circuit as necessary, then go to step 6 . If circuit is okay, go to next step.
5. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . After replacing PCM, go to next step.
6. Using scan tool, clear DTCs. Start engine and let it idle until normal operating temperature is reached. Using scan tool, select SPECIFIC DTC function for this DTC. Operate vehicle under conditions required to set DTC until scan tool indicates that diagnostic ran. If diagnostic passed, go to next step. If diagnostic did not pass, go to step 2 .
7. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, go to perform appropriate test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs that have not been diagnosed, system is okay.

An overcharging condition may set this DTC. Perform ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If problem is intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Output Driver Modules (ODM) are chips that are inside the PCM. ODMs provide grounded outputs that control devices. Each output has an internal feedback circuit that connects to the PCM microprocessor. ODM 3 determines if the voltage or the current may cause damage to the PCM. The PCM monitors voltage through the ignition 1 input. Any incorrect current that is on a circuit to the ODM will cause the ODM to report this DTC.

PCM will run diagnostic for this DTC when ignition is on. DTC will set when the ODM has detected a voltage more than 33 volts, or excessive current is detected on any circuit to the ODM. Condition must be present for 30 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) . After performing powertrain diagnostic system check, go to next step.
2. Check if DTC P0560 is set. If DTC P0560 is set, perform ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If DTC P0560 is not set, go to next step.
3. Using scan tool, select OUTPUT DRIVER DATA list. Observe scan tool parameters. If any parameters indicate a fault is present, go to next step. If no parameters indicate a fault is present, go to step 5 .
4. Check for short to voltage on control circuit for component that indicated a fault. Repair circuit as necessary, then go to step 6 . If circuit is okay, go to next step.
5. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . After replacing PCM, go to next step.
6. Using scan tool, clear DTCs. Start engine and let it idle until normal operating temperature is reached. Using scan tool, select SPECIFIC DTC function for this DTC. Operate vehicle under conditions required to set DTC until scan tool indicates that diagnostic ran. If diagnostic passed, go to next step. If diagnostic did not pass, go to step 2 .
7. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, go to perform appropriate test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs that have not been diagnosed, system is okay.

An overcharging condition may set this DTC. Perform ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If problem is intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Output Driver Modules (ODM) are chips that are inside the PCM. ODMs provide grounded outputs that control devices. Each output has an internal feedback circuit that connects to the PCM microprocessor. ODM 4 determines if the voltage or the current may cause damage to the PCM. The PCM monitors voltage through the ignition 1 input. Any incorrect current that is on a circuit to the ODM will cause the ODM to report this DTC.

PCM will run diagnostic for this DTC when ignition is on. DTC will set when the ODM has detected a voltage more than 33 volts, or excessive current is detected on any circuit to the ODM. Condition must be present for 30 seconds.

1. Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__powertrain-diagnostic-system-check) . After performing powertrain diagnostic system check, go to next step.
2. Check if DTC P0560 is set. If DTC P0560 is set, perform ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If DTC P0560 is not set, go to next step.
3. Using scan tool, select OUTPUT DRIVER DATA list. Observe scan tool parameters. If any parameters indicate a fault is present, go to next step. If no parameters indicate a fault is present, go to step 5 .
4. Check for short to voltage on control circuit for component that indicated a fault. Repair circuit as necessary, then go to step 6 . If circuit is okay, go to next step.
5. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l) . After replacing PCM, go to next step.
6. Using scan tool, clear DTCs. Start engine and let it idle until normal operating temperature is reached. Using scan tool, select SPECIFIC DTC function for this DTC. Operate vehicle under conditions required to set DTC until scan tool indicates that diagnostic ran. If diagnostic passed, go to next step. If diagnostic did not pass, go to step 2 .
7. Using scan tool, observe all stored information. If scan tool displays any DTCs that have not been diagnosed, go to perform appropriate test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__diagnostic-trouble-code-definitions) . If scan tool does not display any DTCs that have not been diagnosed, system is okay.

An overcharging condition may set this DTC. Perform ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If problem is intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

Ignition 1 voltage is supplied from the fuse block to the Instrument Panel Cluster (IPC) by the ignition 1 voltage circuit. The PCM controls the hot coolant indicator by grounding the hot coolant indicator control circuit via the underhood accessory wiring junction block. If the fault detection circuit senses a voltage other than what is expected, DTC P1673 will set. The PCM will monitor the control circuit for a short to ground, a short to voltage or an open circuit.

PCM will run diagnostic for this DTC when ignition is on and system voltage is 9-18 volts. DTC will set when an improper voltage level has been detected on the hot coolant indicator control circuit. Condition must be present for at least 30 seconds.

1. Perform engine cooling diagnostic system check. See «ENGINE COOLING DIAGNOSTIC SYSTEM CHECK»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l__engine-cooling-diagnostic-system-check) under SELF-DIAGNOSTIC SYSTEM. After performing engine cooling diagnostic system check, go to next step.
2. Turn ignition on. Using scan tool, command ENGINE HOT light on and off. If ENGINE HOT light turns on and off with each command, see «DIAGNOSTIC AIDS»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). If ENGINE HOT light does not turn on and off with each command, go to next step.
3. Turn ignition off. Disconnect Instrument Panel Cluster connector. Turn ignition on. Connect a test light between ground and IPC harness connector C2 terminal "I" (Pink wire). (Scheme 8) If test light illuminates, go to next step. If test light does not illuminate, go to step 10.
4. Connect test light between IPC harness connector C2 terminal "I" (Pink wire) and IPC harness connector C1 terminal "Q" (Dark Green wire). Using scan tool, command ENGINE HOT light on and off. If test light turns on and off with each command, go to step 8. If test light does not turn on and off with each command, go to next step.
5. If test light stays on with each command, go to step 7. If test light does not stay on with each command, go to next step.
6. Check for open or short to voltage in ENGINE HOT light control circuit (Dark Green wire) between IPC harness connector C1 terminal "Q" and PCM harness connector C1 terminal No. 75. (Scheme 3)and (Scheme 6). Repair circuit as necessary, then go to step 13. If circuit is okay, go to step 9.
7. Check for short to ground in ENGINE HOT light control circuit (Dark Green wire) between IPC harness connector C1 terminal "Q" and PCM harness connector C1 terminal No. 75. (Scheme 3)and (Scheme 6). Repair circuit as necessary, then go to step 13. If circuit is okay, go to step 9.
8. Check for poor connections at IPC. If a problem is found, repair as necessary, then go to step 13. If a problem is not found, go to step 11.
9. Check for poor connections at PCM harness connector. Repair as necessary. After repairs, go to step 13. If connections are okay, go to step 12.
10. Repair feed circuit to IPC. After repairs, go to step 13.
11. Replace ENGINE HOT light bulb. After repairs, go to step 13.
12. Replace PCM. Program replacement PCM using required equipment. See «PROGRAMMING»(/chevrolet/malibu/v-2000-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-31l-34l). After replacing PCM, go to next step.
13. Using scan tool, select CLEAR INFO or CLEAR DTCs function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for this DTC until DTC test runs. If scan tool indicates FAILED THIS IGN, repeat step 2. If scan tool does not indicate FAILED THIS IGN, repair is complete.

If problem is intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION under SELF-DIAGNOSTIC SYSTEM.

See also:
• MODEL IDENTIFICATION
• DIAGNOSTIC PROCEDURE
• POWERTRAIN DIAGNOSTIC SYSTEM CHECK
• DIAGNOSTIC TROUBLE CODE DEFINITIONS
• CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE
• PROGRAMMING THEFT DETERRENT SYSTEM COMPONENTS
• ENABLE CRITERIA
• P0481
• P1112
• CODE TYPES
• PCM LOCATION
• INTERMITTENT TROUBLE CODE DETERMINATION
• ENGINE COOLING DIAGNOSTIC SYSTEM CHECK