Engine Control System Self-Diagnostics - 2.0L & 2.5L: Diagnosis

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, the Malfunction Indicator Light (MIL) located on instrument cluster will illuminate.

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.

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

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 under SYSTEM CHECKS.

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

Ensure all engine systems not related to computer system are operating properly. DO NOT proceed with testing unless all other problems have been repaired. Diagnostic system check must be performed before using specific DTC testing procedure. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) .
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.
After necessary repairs are made, clear DTCs, verify vehicle will enter "closed-loop" operation and ensure DTC does not reset.

RETRIEVING DIAGNOSTIC TROUBLE CODES

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

Scheme 1

Scheme 1: RETRIEVING DIAGNOSTIC TROUBLE CODES

POWERTRAIN DIAGNOSTIC SYSTEM CHECK

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

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. Repair as necessary. After repairs, go to next step.
Turn ignition on, with engine off. Using scan tool, attempt to establish communication with PCM. If scan tool communicates with PCM, go to next step. If scan tool does not communicate with PCM, perform SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article.
Attempt to start engine. If engine starts and idles, go to next step. If engine does not start, go to appropriate NO-START DIAGNOSIS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
Using scan tool, select DTC INFO. If scan tool displays any powertrain DTCs, go to next step. If scan tool does not display any powertrain DTCs, go to step 7 .
Using scan tool, save or capture powertrain DTC Information, Store Information. After saving DTC information, go to next step.
If scan tool displays DTC P0601, go to «DTC P0601: PCM MEMORY (2.0L)»(ref-99188-S31034444732001062700000) or «DTC P0601-P0607, P1600, P1621, P1627 OR P1683: PCM MEMORY (2.5L)»(ref-99188-S08126666152001070200000) . If other than DTC P0601 is set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) .
If problem is related to automatic transmission, diagnose transmission. See appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS. If problem is not related to automatic transmission, go to next step.
If problem is related with I/M testing, go to «INSPECTION/MAINTENANCE PROCEDURES»(ref-99188-S42075017972001101500000) . Repair as necessary. If problem is other than I/M testing, go to next step.
Check for cause of hard start, surges/chuggles, lack of power, sluggishness, or sponginess. Check for cause of detonation/spark knock, hesitation, sag, stumble, cuts out/misses, poor fuel economy, poor fuel fill quality, rough, unstable, or incorrect idle and stalling. Check for cause of dieseling/run-on, backfire, MIL inoperative, or MIL is always on. Repair as necessary. If no problem is found, problem is intermittent.

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.

SCAN TOOL USAGE

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

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

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

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

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

Diagnostic Procedures

Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Review any service bulletins for software updates that may prevent I/M readiness. Perform any reprogramming or repairs indicated by the service bulletins. If reprogramming or repair service was required, go to «INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE»(ref-99188-S38039229032001101500000) . If reprogramming or repair service was not required, go next step.
Using scan tool, observe the I/M System Status display. If more than one test is indicating a NO status, go to «INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE»(ref-99188-S38039229032001101500000) . If a YES status is indicated, go to appropriate INSPECTION/MAINTENANCE SYSTEM SET procedure for the indicated system.

Conditions For Running DTC

Ensure vehicle meets the following conditions before performing procedure

Barometric pressure is greater than 22 in. Hg (75 kPa).
Engine coolant temperature is at least 158°F (70°C) after engine warm-up.
Battery voltage is 10.5-16.0 volt
Vehicle has been driven for at least 20 minutes.
Fuel level is 1/4-3/4 tank.

Test will initiate only after a cold start. A cold start is considered when engine coolant temperature is less than 35°F (2°C).

Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Turn off all accessories (e.g. A/C, blower fan, etc.). Set vehicle parking brake. Ensure transmission is in Park (A/T) or Neutral (M/T). Start engine. Allow engine to idle for 2 minutes or until engine reaches normal operating temperature of at least 158°F (70°C). Accelerate vehicle at part throttle to 30-50 MPH. Maintain speed for 2 minutes or until I/M system status indicator updates to YES. After completing actions, go to next step.
Accelerate vehicle at part throttle to 45-60 MPH. Maintain this speed without changing throttle position for 2-3 minutes or until I/M system status updates to YES. After completing actions, go to next step.
In order for this test to run, vehicle must operate in the following conditions, then go to next step: Accelerate vehicle at part throttle to 30-40 MPH. Maintain this speed without changing throttle position for 3 minutes.
Accelerate vehicle at part throttle to 50-60 MPH and maintain speed for 3-5 minutes or until I/M system status indicator updates to YES, then go to next step.
In order for this test to run, vehicle must operate in the following conditions: Operate engine at idle until it reaches operating temperature of at least 158°F (70°C). Accelerate vehicle at part throttle to 35-55 MPH. Operate vehicle for 20 minutes at speeds of 35 MPH or more. Operate vehicle for 3 minutes at 30-50 MPH with throttle position steady. Using scan tool, observe I/M system status display. If status displays YES, go to next step.
Using scan tool, observe I/M system status display. If all I/M system status indicators update to YES, go to next step. If not all I/M system status indicators update to YES, go to I/M system set procedure for the indicated systems.
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»(ref-99188-S14830162302001070200000) . If scan tool does not indicate emission related DTCs, system is okay.

Barometric pressure is greater than 75 kPa.
Engine coolant temperature is 158-230°F (70-110°C).
Intake air temperature is greater than 18°F (-8°C).
Battery voltage is 10.5-16.0 volts.

Failure to meet the necessary requirements may produce inaccurate test results.

Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Operate engine at normal operating temperature and at idle for one minute. Turn off all accessories. Accelerate vehicle at part throttle to 45-60 MPH and maintain speed for 2-3 minutes or until I/M System Status indicates YES. Using scan tool, observe I/M System Status display. If catalyst system status updates to YES, go to step 5 . If catalyst system status does not update to YES, go to next step.
Using scan tool, observe DTC Information. If DTCs are set, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no DTCs are set, go to next step.
Using scan tool, observe the NOT RAN SINCE CODE CLEARED display. Determine which of the DTCs required for a YES status has not run. Enter DTC in Specific DTC menu on scan tool. Operate vehicle within Conditions for Running DTC. Repeat procedure until scan tool indicates the diagnostic test has run. Repeat this step for any additional required DTCs that have not run. Using scan tool, observe I/M System Status display. If status updates to YES, go next step. If status does not update to YES, see repeat test until I/M System Status updates to YES.
Using scan tool, observe emission related DTC portion of I/M System Status display. If scan tool indicates any emission related DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no DTCs are displayed, system is okay.

Barometric pressure is greater than 75 kPa.
Engine coolant temperature is 158-230°F (70-110°C) after engine warm-up.
Intake air temperature is greater than 18°F (-8°C).

Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Operate engine at idle until engine reaches operating temperature of at least 158°F (70°C). This may take up to 8-10 minutes, depending on start-up coolant temperature. Accelerate vehicle at part throttle to 30-40 MPH. Maintain this speed without changing throttle position for 3 minutes. Using scan tool, observe I/M System Status display. If display updates to YES, go to step 5 . If display does not update to YES, go to next step.
Using scan tool, observe DTC Information. If scan tool indicates any failed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no DTCs are set, go to next step.
Using scan tool, observe the NOT RAN SINCE CODE CLEARED display. Determine which of the DTCs required for a YES status has not run. Operate vehicle within Conditions For Running DTC. Monitor status of DTCs that are necessary to complete the test in the NOT RAN SINCE CODE CLEARED display of scan tool. Repeat this procedure until scan tool indicates that diagnostic test has run. Repeat this step for any additional required DTCs that have not run. Using scan tool, observe I/M System Status display. If EGR System Status updates to YES, go to next step. If status does not update to YES, go to «DIAGNOSTIC AIDS»(ref-99188-S04480554712001101500000) .
Using scan tool, observe the emission related DTC portion of I/M System Status display. If scan tool indicates any emission related DTCs set, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no DTCs are displayed, system is okay.

Diagnostic Aids

A correctly operating MAP sensor is necessary for accurate EGR system diagnostics.

The I/M System Status does not indicate whether the test has passed or failed, only that a decision was made. When all of the diagnostics for a specific system have run and passed, the I/M System Status will update to YES. If a test for a specific system has failed, the 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, the emission related DTC portion of I/M System Status display will indicate that MIL is requested. The I/M System Status also registers the number of DTCs.

Barometric pressure is greater than 75 kPa.
Engine coolant temperature is at least 158°F (70°C) after engine warm-up.
Fuel level is 1/4-3/4.
Battery voltage is 10.5-16.0 volts.
Vehicle has been driven for at least 20 minutes.

Test will initiate only after a cold start. A cold start is considered when ECT less than 35°F (2°C). Failure to meet the necessary requirements may produce inaccurate test results.

Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Operate engine at idle until engine reaches operating temperature of at least 158°F (70°C). This may take up to 8-10 minutes, depending on start-up coolant temperature. Accelerate vehicle at part throttle to 35-55 MPH. Operate vehicle for 20 minutes at 35 MPH or more. Operate vehicle for 3 minutes at 30-50 MPH with throttle position steady. Using scan tool, observe I/M System Status display. If display updates to YES, go to step 5 . If display does not update to YES, go to next step.
Using scan tool, observe DTC Information. If scan tool indicates any failed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no DTCs are set, go to next step.
Using scan tool, observe the NOT RAN SINCE CODE CLEARED display. Determine which of the DTCs required for a YES status has not run. Operate vehicle within the Conditions For Running DTC. Repeat procedure until scan tool indicates the diagnostic test has run. Repeat this step for any additional required DTCs that have not run. Using scan tool, observe I/M System Status display. If EVAP System Status updates to YES, go to next step. If status does not update to YES, see «DIAGNOSTIC AIDS»(ref-99188-S30477671122001101500000) .
Using scan tool, observe the emission related DTC portion of I/M System Status display. If scan tool indicates any emission related DTCs set, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no DTCs are displayed, 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 the test. A loose fuel cap may cause a service bay test to abort or fail and prevent the I/M System Status from updating. A failed or aborted test will require vehicle to cool down in order to meet the enable criteria to run another test.

Engine coolant temperature is at least 158°F (70°C).
Engine operating in closed-loop.
Battery voltage is 10.5-16.0 volts.

Failure to meet the necessary requirements may produce inaccurate test results.

Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
In order for this test to run, operate vehicle in the following conditions: Accelerate vehicle to 50-60 MPH and cruise for 3-5 minutes after engine reaches operating temperature or when I/M System Status updates to YES. Using scan tool, review I/M System Status display. If display updates to YES, go to step 5 . If display does not update to YES, go to next step.
Using scan tool, observe DTC Information. If scan tool indicates any failed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If scan tool does not indicate any failed DTCs, go to next step.
Using scan tool, observe the NOT RAN SINCE CODE CLEARED display. Determine which of the DTCs required for a YES status has not run. Operate vehicle within Conditions For Running DTC. Monitor status of DTCs that are necessary to complete the test in the NOT RAN SINCE CODE CLEARED display of scan tool. Repeat procedure until scan tool indicates the diagnostic test has run. Repeat this step for any additional required DTCs that have not run. Using scan tool, observe I/M System Status display. If HO2S/O2S System Status updates to YES, go to next step. If status does not update to YES, see «DIAGNOSTIC AIDS»(ref-99188-S14323661272001101500000) .
Using scan tool, observe the emission related DTC portion of the I/M System Status display. If scan tool indicates any emission related DTCs are set, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If scan tool does not indicate any emission related DTCs are set, system is okay.

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

The I/M System Status does not indicate whether test has passed or failed, only that a decision was made. When all of the 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, the emission related DTC portion of the I/M System Status display will indicate that MIL is requested. The I/M System Status also registers the DTCs.

Engine is running engine at normal operating temperature of 158-230°F (70-110°C).
Battery voltage is 10.5-16.0 volts.

Failure to meet the necessary requirements may produce inaccurate test results.

Perform powertrain diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Start and operate engine at idle. Ensure vehicle is within the Conditions For Running DTC. Set vehicle parking brake. Place transmission in Park (A/T) or Neutral (M/T). Turn off all of accessories (e.g., A/C, blower fan, etc.). Operate engine at idle until it reaches operating temperature of at least 158°F (70°C). Accelerate vehicle at part throttle to 30-50 MPH. Maintain speed for 2 minutes or until I/M System Status indicator updates to YES. If status updates to YES, go to step 5 . If status does not update to YES, go to next step.
Using scan tool, observe DTC information. If scan tool indicates any failed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If scan tool does not indicate any failed DTCs, go next step.
Using scan tool, observe the NOT RAN SINCE CODE CLEARED display. Determine which of the DTCs required for a YES status has not run. Operate vehicle within the Conditions For Running DTC. Monitor status of DTCs that are necessary to complete the test in the NOT RAN SINCE CODE CLEARED display of scan tool. Repeat procedure until scan tool indicates that all the necessary DTC diagnostic tests have run. Using scan tool, observe I/M System Status display. If HO2S Heater System Status updates to YES, go to next step. If status does not update to YES, go to «DIAGNOSTIC AIDS»(ref-99188-S14246398662001101500000) .
Using scan tool, observe emission related DTC portion of I/M System Status display. If scan tool indicates any emission related DTCs are set, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no DTCs are set, system is okay.

The HO2S heater tests will normally run within the 2 minutes allotted in the procedure. If there is an indeterminate condition, test may take up to 8 minutes on some vehicles before a decision of pass or fail is made. If test does not update within the 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 the loss of enabling conditions. Extremely high ambient temperatures may prevent HO2S heater test from initiating.

DIAGNOSTIC TROUBLE CODE DEFINITIONS

Note. DTCs are retrieved using a Tech 2 scan tool, or other OBD-II compatible scan tool connected to OBD-II 16-pin Data Link Connector (DLC).

DTC	Definition	(1) Type
BXXXX	Body Control System Malfunction	(2)
CXXXX	Chassis Control System Malfunction	(2)
P0101	MAF Sensor Performance	B
P0102	MAF Sensor Circuit - Low Frequency	A
P0103	MAF Sensor Circuit - High Frequency (2.0L)	A
P0103	MAF Sensor Circuit - High Frequency (2.5L)	A
P0111	IAT Sensor Performance	B
P0112	IAT Sensor Circuit - Low Voltage	A
P0113	IAT Sensor Circuit - High Voltage	A
P0116	ECT Sensor Circuit Performance	B
P0117	ECT Sensor Circuit - Low Voltage	A
P0118	ECT Sensor Circuit - High Voltage	A
P0121	Throttle Position Sensor Performance	B
P0122	TP Sensor Circuit - Low Voltage	A
P0123	TP Sensor Circuit - High Voltage	A
P0125	ECT Excessive Time To Enter Closed Loop	B
P0131	HO2S No. 1 Circuit - Low Voltage (2.0L)	B
P0131	HO2S No. 1 Circuit - Low Voltage (2.5L)	B
P0132 Or P0152	HO2S No. 1 Circuit - High Voltage	B
P0133 Or P0153	HO2S No. 1 Slow Response	B
P0134	HO2S No. 1 Circuit Insufficient Activity (2.0L)	B
P0134 Or P0154	HO2S No. 1 Circuit Insufficient Activity (2.5L)	B
P0135	HO2S No. 1 Heater Circuit (2.0L)	B
P0135 Or P0155	HO2S No. 1 Heater Circuit (2.5L)	B
P0136	HO2S No. 2 Circuit (2.0L)	B
P0136 Or P0156	HO2S No. 2 Circuit (2.5L)	B
P0141	HO2S No. 2 Heater Performance (2.0L)	B
P0141	HO2S No. 2 Heater Performance - Bank 1 (2.5L)	B
P0161	HO2S No. 2 Heater Performance - Bank 2 (2.5L)	B
P0171	Lean Fuel Trim System (2.0L)	B
P0171	Lean Fuel Trim System (2.5L)	B
P0172	Rich Fuel Trim System	B
P0174	Lean Fuel Trim System - Bank 2 (2.5L)	B
P0175	Rich Fuel Trim System - Bank 2 (2.5L)	B
P0300	Engine Misfire Detected	B
P0301	Cylinder No. 1 Misfire Detected (2.0L)	B
P0301	Cylinder No. 1 Misfire Detected (2.5L)	B
P0302	Cylinder No. 2 Misfire Detected (2.0L)	B
P0302	Cylinder No. 2 Misfire Detected (2.5L)	B
P0303	Cylinder No. 3 Misfire Detected (2.0L)	B
P0303	Cylinder No. 3 Misfire Detected (2.5L)	B
P0304	Cylinder No. 4 Misfire Detected (2.0L)	B
P0304	Cylinder No. 4 Misfire Detected (2.5L)	B
P0305	Cylinder No. 5 Misfire Detected (2.5L)	B
P0306	Cylinder No. 6 Misfire Detected (2.5L)	B
P0327	Knock Sensor Circuit - Voltage Low (2.0L)	A
P0328	Knock Sensor Circuit - Open (2.0L)	A
P0335	Crankshaft Position Sensor Circuit	A
P0340	Camshaft Position Sensor Circuit	A
P0400	EGR Flow Malfunction (2.0L)	B
P0400	EGR Flow Malfunction (2.5L)	B
P0403	EGR Solenoid Control Circuit (2.0L)	A
P0420	Catalyst System Low Efficiency (2.0L)	B
P0420 Or P0430	Catalyst System Low Efficiency (2.5L)	B
P0440	EVAP System With ORVR (2.0L & 2.5L)	B
P0440	EVAP System Without ORVR (2.0L)	B
P0443	EVAP System Incorrect Purge Flow (2.0L)	B
P0450	Fuel Tank Pressure Sensor Circuit	B
P0451	Fuel Tank Pressure Sensor Performance - With ORVR (2.0L)	B
P0455	EVAP System Leak Detected - With ORVR	A
P0455	EVAP System Leak Detected - Without ORVR (2.0L)	A
P0461 (3)	Fuel Level Sensor Performance	B
P0463 (3)	Fuel Level Sensor Circuit - High Voltage	B
P0500 (4)	Vehicle Speed Sensor Circuit	B
P0505	Idle Control System	A
P0601	PCM Memory (2.0L)	A
P0601-P0607, P1600, P1621, P1627 Or P1683	PCM Memory (2.5L)	A
P0705	Transmission Range Switch	B
P0720 (4)	No Output Shaft Speed Sensor Signal Received	B
P0741 (4)	Torque Converter Clutch Signal	B
P0743 (4)	Torque Converter Clutch Control Solenoid	A
P0751 (4)	Gear Change Control From PCM-To-Transmission Does Not Agree With Actual Gear Position	B
P0753 (4)	A/T Shift Solenoids	A
P0756 (4)	Gear Change Control From PCM-To-Transmission Does Not Agree With Actual Gear Position	B
P0758 (4)	A/T Shift Solenoid No. 2	A
P1408	MAP Sensor Circuit	B
P1410	EVAP Tank Pressure Control Solenoid Circuit (2.0L)	B
P1450	BARO Sensor Circuit	A
P1451	BARO Sensor Performance	B
P1500	Start Switch Circuit	B
P1510	PCM Backup Power Supply (2.0L)	A
P1510	PCM Backup Power Supply (2.5L)	A
P1875 (4)	4WD Low Position Circuit Malfunction	B
(1) See appropriate CODE TYPES under ON-BOARD DIAGNOSTICS in SELF-DIAGNOSTIC SYSTEM. (2) For a complete listing of body and chassis codes, see appropriate BODY CONTROL MODULES article inACCESSORIES & EQUIPMENT. (3) See appropriate ANALOG INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. (4) See appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS.

(1)	See appropriate CODE TYPES under ON-BOARD DIAGNOSTICS in SELF-DIAGNOSTIC SYSTEM.

(2)	For a complete listing of body and chassis codes, see appropriate BODY CONTROL MODULES article inACCESSORIES & EQUIPMENT.

(3)	See appropriate ANALOG INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT.

(4)	See appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS.

DIAGNOSTIC TROUBLE CODE DEFINITIONS

DIAGNOSTIC TESTS

Note. Before clearing DTCs, perform 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. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE under PROGRAMMING.

Note. For component locations, see appropriate SYSTEM & COMPONENT TESTING article.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Turn ignition off. Check for intake manifold leak, object blocking MAF sensor inlet screen, throttle body vacuum leaks, EGR vacuum leaks, PCV valve problem (missing, faulty, or incorrectly installed). Repair as necessary. After repairs, go to step 13. If problem does not exist, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If DTC P0101 is set, go to next step. If DTC P0101 is not set, go to «DIAGNOSTIC AIDS»(ref-99188-S35128765082001062700000).
Turn ignition off. Disconnect MAF sensor harness connector. Turn ignition on, with engine off. Using a test light connected to ground, probe MAF sensor harness connector terminal No. 1 (Blue/Black wire) on 2.0L or terminal No. 3 (Blue/Black wire) on 2.5L. see scheme 2 If test light illuminates, go to next step. If test light does not illuminate, go to step 9.
Connect test light between MAF sensor harness connector terminals No. 1 (Blue/Black wire) and No. 3 (Purple/Green wire) on 2.0L, or terminals No. 2 (Gray/Yellow wire) and No. 3 (Blue/Black wire) on 2.5L. If test light illuminates, go to next step. If test light does not illuminate, go to step 10.
Turn ignition off. Reconnect MAF sensor harness connector. Turn ignition on, with engine off. Using DVOM connected to ground, backprobe PCM harness connector C2 terminal No. 10 (Purple/White wire) on 2.0L or terminal No. 23 (Purple/White wire) on 2.5L. see scheme 3or see scheme 4. If voltage reading is 1.0-1.6 volts, go to next step. If voltage reading is not 1.0-1.6 volts, go to step 8.
Turn ignition off. Check for poor connections at PCM and MAF sensor connectors. Repair as necessary. After repairs, go to step 13. If connections are okay, go to step 12.
Turn ignition off. Check for open or short in Purple/White wire between MAF sensor and PCM. Check for poor connection at MAF sensor. Repair as necessary. After repairs, go to step 13. If circuit and connection are okay, go to step 11.
Turn ignition off. Repair open in Blue/Black wire between MAF sensor and power supply. After repairs, go to step 13.
Turn ignition off. Repair open in Purple/Green wire on 2.0L or Gray/Yellow wire on 2.5L between MAF sensor and PCM. After repairs, go to step 13.
Replace MAF sensor. After replacing sensor, go to step 13.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
After repairs, clear DTCs. Operate vehicle within FREEZE FRAME conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000).

Check for a skewed or stuck TP sensor. A faulty TP sensor or sensor circuit can cause PCM to incorrectly calculate the predicted mass air flow value. If scan tool indicates throttle angle reading of 0-13 percent with throttle closed, check for the following conditions and repair as necessary.

Throttle plate sticking or excessive deposits on throttle plate or throttle bore.
TP sensor signal circuit shorted to voltage.
A poor connection or high resistance in TP sensor ground circuit.
Wiring harness misrouted near spark plug wires.
Damaged wiring harness.
Plugged intake air duct or a dirty air filter element. A WOT acceleration from a stop should cause mass air flow parameter to increase from about 2-3.5 grams/second at idle to about 100 grams/second or greater at time of 1-2 shift.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Check harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement. Intermittent may also be caused by a fault in MAF sensor circuit. Inspect wiring harness and components for an intermittent condition.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Start engine. With throttle closed, select MAF sensor parameter on scan tool. If MAF sensor parameter is within 2.5-4.6 grams/second, go to next step. If MAF sensor parameter is not within 2.5-4.6 grams/second, go to step 4.
Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the conditions for running the DTC or until the DTC diagnostic has run. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S16761176982001062700000).
Turn ignition off. Disconnect MAF sensor harness connector. Turn ignition on, with engine off. Using a DVOM, check voltage between MAF sensor harness connector terminals No. 1 (Blue/Black wire) and No. 3 (Purple/Green wire) on 2.0L or terminals No. 2 (Gray/Yellow wire) and No. 3 (Blue/Black wire) on 2.5L. see scheme 2 If voltage reading is about battery voltage, go to next step. If voltage reading is not about battery voltage, go to step 6.
Turn ignition off. Reconnect MAF sensor harness connector. Start and operate engine at idle. Using DVOM, backprobe MAF sensor harness connector terminal No. 2 (Purple/White wire) on 2.0L or terminal No. 1 (Purple/White wire) on 2.5L. If voltage reading is within 1.5-1.8 volts, go to step 9. If voltage reading is not within 1.5-1.8 volts, go to step 7.
Turn ignition off. Repair open or short in Blue/Black wire between MAF sensor and voltage supply. After repairs, go to step 10.
Turn ignition off. Check for short or open in Purple/White wire between PCM and MAF sensor. Check for poor connection at MAF sensor. Repair as necessary. After repairs, go to step 10. If no problem is found, go to next step.
Replace MAF sensor. After replacing sensor, go to step 10.
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
After repairs, clear DTCs. Operate vehicle within FREEZE FRAME conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000).

Check for wiring harness misrouted near spark plug wires, damaged wiring harness, and/or a restriction in air intake. An acceleration from a stop should cause MAF sensor parameter to increase.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Start engine. With throttle closed, observe MAF sensor parameter on scan tool. If scan tool display is not more than 2.0-4.0 grams/second, go to step 4. If scan tool display is more than 2.0-4.0 grams/second, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If this DTC resets, go to next step. If this DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S17830121672001062700000).
Turn ignition on, with engine off. Using DVOM connected to ground, backprobe PCM harness connector C2 terminal No. 10 (Purple/White wire). see scheme 3 If voltage reading is 1.0-1.6 volts, leave DVOM connected and go to next step. If voltage reading is not 1.0-1.6 volts, go to step 6.
Start engine. Momentarily increase engine speed to 4000 RPM while observing DVOM. If voltage reading increases from 1.6 volts at idle to about 3 volts at 4000 RPM, go to step 10. If voltage reading does not increase from 1.6 volts at idle to about 3 volts at 4000 RPM, go to step 11.
Turn ignition off. Disconnect MAF sensor harness connector. Using a test light connected to battery voltage, probe MAF sensor harness connector terminal No. 3 (Purple/Green wire). see scheme 2 If test light illuminates, go to next step. If test light does not illuminate, go to step 8.
Check for poor connections at MAF sensor and PCM. Repair as necessary. After repairs, go to step 12. If connection is okay, step 9.
Repair open in Purple/Green wire. After repairs, go to step 12.
Check for short in Purple/White wire between MAF sensor and PCM. Repair as necessary. After repairs, go to step 12. If circuit is okay, go to step 11.
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to step 12.
Turn ignition off. Replace MAF sensor. After replacing sensor, go to next step.
After repairs, clear DTCs. Operate vehicle within FREEZE FRAME conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000).

Check for wiring harness misrouted near spark plug wires, damaged wiring harness, and/or a restriction in air intake. An acceleration from a stop should cause MAF sensor parameter to increase from about 2.0-3.5 grams/second at idle to about 5.0-9.0 grams/second at 2500 RPM.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Start engine. With throttle closed, select MAF sensor parameter on scan tool. If MAF parameter is greater than 2.5-4.6 grams/second, go to step 4. If MAF parameter is not greater than 2.5-4.6 grams/second, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTC information function. Operate vehicle within FREEZE FRAME conditions. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S11348186912001063000000).
Operate engine at idle. Using a DVOM, backprobe MAF sensor harness connector terminal No. 1 (Purple/White wire). see scheme 2 If voltage reading is 1.5-1.8 volts, go to next step. If voltage reading is not 1.5-1.8 volts, go to step 6.
Leave DVOM connected. Check voltage while briefly increasing engine speed to about 4000 RPM. If voltage increases to about 3.0 volts, go to step 10. If voltage does not increase to about 3.0 volts, go to step 11.
Turn ignition off. Disconnect MAF sensor harness connector. Using a test light connected to ground, probe MAF sensor harness connector terminal No. 2 (Gray/Yellow wire). see scheme 2 If test light illuminates, go to next step. If test light does not illuminate, go to step 8.
Check for faulty connection at MAF sensor and at PCM. Repair as necessary. After repairs, go to step 12. If connections are okay, go to step 9.
Repair open in Gray/Yellow wire between MAF sensor and PCM. After repairs, go to step 12.
Check for short in Purple/White wire between MAF sensor and PCM. Repair as necessary. After repairs, go to step 12. If circuit is okay, go to step 11.
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Replace MAF sensor. After replacing sensor, go to next step.
After repairs, clear DTCs. Operate vehicle within FREEZE FRAME conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000).

Check is MAF sensor readings vary with air temperature and barometric pressure. The specifications indicated are at 68°F (20°C) and at sea level. Check for misrouted wiring harness. Ensure MAF sensor harness is not routed too close to high voltage wires such as spark plug leads. Inspect wiring harness for damage. If harness appears to be okay, observe scan tool while moving the connectors and wiring harnesses related to MAF sensor. A change in display will indicate location of the fault. Check for a plugged intake air duct or a dirty air filter element. An acceleration from a stop should cause MAF displayed on scan tool to increase from about 2.0-3.5 grams/second at idle to 5.0-9.0 grams/seconds at 2500 RPM.

If DTC is intermittent, road test vehicle while monitoring DTC P0103 diagnostic on scan tool under the NOT RAN SINCE CODE CLEARED selection in the DTC Information menu. If DTC P0103 appears in the NOT RAN SINCE CODE CLEARED list, the P0103 diagnostic has not yet run. When DTC P0103 does not appear in the NOT RAN SINCE CODE CLEARED list, P0103 diagnostic has run. If MIL is NOT illuminated, and there is no pending DTC status in DTC Information, the P0103 diagnostic has passed. DTCs MUST be cleared in order to view the current status of the NOT RAN SINCE CODE CLEARED list and indicates whether or not the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status, in order to determine the outcome of the diagnostic test involved. An intermittent malfunction may be caused by a fault in the MAF sensor circuit. Inspect wiring harness and components for an intermittent condition.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Turn ignition off. Allow engine to cool to ambient air temperature. Turn ignition on, with engine off. Using scan tool, compare IAT sensor value with ambient air temperature. If scan tool displays IAT sensor value within 0-9°F (0-5°C) of ambient temperature, go to next step. If scan tool does not display IAT sensor value within 0-9°F (0-5°C) of ambient temperature, go to step 4 .
Remove IAT sensor from air cleaner housing, leaving harness connector connected. Wrap a cool, damp shop towel around sensor to lower sensor temperature while observing scan tool. Remove shop towel. Wrap a warm shop towel around sensor to increase sensor temperature while observing scan tool. If scan tool reading skipped, jumped or remained constant during test, go to step 9 . If scan tool reading did not skip, jump or remain constant during test, see «DIAGNOSTIC AIDS»(ref-99188-S32418967662001062700000) .
Disconnect IAT sensor harness connector. Connect a fused jumper wire between IAT harness connector terminals. If scan tool displays 329°F (165°C) on 2.0L, or 401°F (205°C) on 2.5L, go to step 9 . If scan tool does not display 329°F (165°C) on 2.0L, or 401°F (205°C) on 2.5L, go to next step.
Turn ignition off. Remove fused jumper wire. Disconnect PCM harness connector C2. Using DVOM, check resistance in Light Blue wire between PCM and IAT sensor harness connector terminal No. 2. If resistance is less than 0.5 ohm, go to next step. If resistance is 0.5 ohm or greater, go to step 7 .
Using DVOM, check resistance between PCM and IAT sensor harness connector terminal No. 1 (Blue/White wire on 2.0L or Gray/Yellow wire on 2.5L). If resistance is less than 0.5 ohm, go to step 10 . If resistance is not less than 0.5 ohm, go to step 8 .
Repair open or high resistance in Light Blue wire between IAT sensor and PCM. Repair as necessary. After repairs, go to step 11 .
Repair open or high resistance in Blue/White wire on 2.0L or Gray/Yellow wire on 2.5L between IAT sensor and PCM. Repair as necessary. After repairs, go to step 11 .
Turn ignition off. Replace IAT sensor. After replacing sensor, go to step 11 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
After repairs, clear DTCs. Operate vehicle within FREEZE FRAME conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) .

Check for a poor PCM harness connection. Check for a shifted IAT sensor. See appropriate SENSOR OPERATING RANGE CHARTS article. A shifted sensor could result in poor driveability complaints.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, observe IAT sensor parameter. If scan tool displays 329°F (165°C) or greater on 2.0L, or 401°F (205°C) or greater on 2.5L, go to step 4 . If scan tool display is not 329°F (165°C) or greater on 2.0L, or 401°F (205°C) or greater on 2.5L, go to next step.
Using scan tool, clear DTC. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S08074872142001062700000) .
Disconnect IAT sensor harness connector. Observe IAT sensor parameter on scan tool. If scan tool displays equal to or less than -40°F (-40°C), go to step 7 . If scan tool display is not equal to or less than -40°F (-40°C), go to next step.
Turn ignition off. Disconnect PCM harness connector C2. Check for short to ground in Light Blue wire between IAT sensor and PCM. Repair as necessary. After repairs, go to step 8 . If circuit is okay, go to next step.
Check for short to ground in Blue/White wire on 2.0L or Gray/Yellow wire on 2.5L between IAT sensor and PCM. Repair as necessary. After repairs, go to step 10 . If circuit is okay, go to step 9 .
Turn ignition off. Replace IAT sensor. After replacing sensor, go to step 10 .
Repair Light Blue wire between IAT sensor and PCM. After repairs, go to step 10 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
After repairs, clear DTCs. Operate vehicle within FREEZE FRAME conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) .

Check for a damaged wiring harness. Check for a shifted IAT sensor. See appropriate SENSOR OPERATING RANGE CHARTS article. A shifted sensor could result in poor driveability complaints.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, observe IAT sensor parameter on scan tool. If scan tool displays -40°F (-40°C) or less, go to step 4 . If scan tool display is not -40°F (-40°C) or less, go to next step.
Using scan tool, clear DTC. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S06031397012001062700000) .
Disconnect IAT sensor harness connector. Connect a fused jumper wire between IAT sensor harness connector terminals. Observe IAT sensor parameter on scan tool. If scan tool displays 329°F (165°C) on 2.0L or 401°F (205°C) on 2.5L, go to step 6 . If scan tool does not display 329°F (165°C) on 2.0L or 401°F (205°C) on 2.5L, go to next step.
Connect a fused jumper wire between chassis ground and IAT sensor harness connector terminal No. 2 (Light Blue wire). Observe IAT sensor parameter on scan tool. If scan tool displays 329°F (165°C) on 2.0L or 401°F (205°C) on 2.5L, go to step 7 . If scan tool does not display 329°F (165°C) on 2.0L or 401°F (205°C) on 2.5L, go to step 8 .
Turn ignition off. Check for poor connection at IAT sensor. Repair as necessary. After repairs, go to step 12 . If connection is okay, go to step 10 .
Turn ignition off. Disconnect PCM harness connectors. Check for open in Blue/White wire on 2.0L or Gray/Yellow wire on 2.5L between IAT sensor and PCM. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to step 9 .
Turn ignition off. Disconnect PCM harness connector C2. Check for open in Light Blue wire between IAT sensor and PCM. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to next step.
Check for poor connections at PCM. Repair as necessary. After repairs, go to step 12 . If connection is okay, go to step 11 .
Replace IAT sensor. After replacing sensor, go to step 12 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
After repairs, clear DTCs. Operate vehicle within FREEZE FRAME conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) .

Check for a damaged wiring harness. Check for a shifted IAT sensor. See appropriate SENSOR OPERATING RANGE CHARTS article. A shifted sensor could result in poor driveability complaints. A short to voltage in IAT sensor input circuit may cause DTC to set.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Retrieve DTCs. If DTC P0117 or P0118 is set, diagnose affected DTCs first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If DTC P0117 or P0118 is not set, go to next step.
Turn ignition off. Check actual engine coolant temperature. Turn ignition on, with engine off. Observe ECT sensor parameter on scan tool. If scan tool displays ECT sensor value near actual coolant temperature, go to step 11. If scan tool does not display ECT sensor value near actual coolant temperature, go to next step.
Disconnect ECT sensor harness connector. Observe ECT sensor parameter on scan tool. If ECT sensor parameter is -40°F (-40°C), go to next step. If ECT sensor parameter is not -40°F (-40°C), go to step 8.
Connect a fused jumper wire between ECT sensor harness connector terminals No. 1 (Orange/Black wire) and No. 3 (Blue/White wire) on 2.0L or terminals No. 1 (Orange/Black wire) and No. 3 (Gray/Yellow wire) on 2.5L. see scheme 5 Observe ECT sensor parameter on scan tool. If scan tool displays 246°F (119°C) on 2.0L or 401°F (205°C) on 2.5L, go to step 13. If scan tool does not display 246°F (119°C) on 2.0L or 401°F (205°C) on 2.5L, go to next step.
Connect a fused jumper wire between chassis ground and ECT sensor harness connector terminal No. 1 (Orange/Black wire). Observe ECT sensor parameter on scan tool. If scan tool displays 246°F (119°C) on 2.0L or 401°F (205°C) on 2.5L, go to next step. If scan tool does not display 246°F (119°C) on 2.0L or 401°F (205°C) on 2.5L, go to step 8.
Turn ignition off. Repair open or high resistance in Blue/White wire on 2.0L or Gray/Yellow wire on 2.5 between ECT sensor and PCM. After repairs, go to step 14. If circuit is okay, go to step 9.
Turn ignition off. Disconnect PCM harness connector C2. Check for short or high resistance in Orange/Black wire between ECT sensor and PCM. Repair as necessary. After repairs, go to step 14. If circuit is okay, go to next step.
Check for poor connections at ECT sensor and PCM. Repair as necessary. After repairs, go to step 14. If circuit is okay, go to next step.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to step 14.
Turn ignition off. Check engine cooling system for improper operation, faulty thermostat, low coolant level, and incorrect coolant. Repair as necessary. After repairs, go to step 14. If problem does not exist, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S36191491232001062700000).
Replace ECT sensor. After replacing sensor, go to next step.
After repairs, clear DTCs. Operate vehicle within FREEZE FRAME conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000).

If DTCs P0106 and P0121 are also set, malfunction may be in sensor ground circuit. Check for proper operation of engine cooling system and coolant level. In cold weather when vehicle is started and sits while warming, a faulty thermostat that stays slightly open can cause this DTC to set. Check for a shifted ECT sensor. See appropriate SENSOR OPERATING RANGE CHARTS article. Check for a poor PCM electrical connection.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, observe ECT parameter on scan tool. If ECT parameter is 329°F (165°C) or greater on 2.0L or 401°F (205°C) or greater on 2.5L, go to step 4 . If ECT parameters is not 329°F (165°C) or greater on 2.0L or 401°F (205°C) or greater on 2.5L, go to next step.
Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S10548573772001062700000) .
Disconnect ECT sensor harness connector. Observe ECT parameter on scan tool. If ECT parameter -40°F (-40°C) or less, go to step 6 . If ECT parameter is not -40°F (-40°C) or less, go to next step.
Turn ignition off. Disconnect PCM harness connectors. Check for short to ground in Orange/Black wire between ECT sensor and PCM. Repair as necessary. After repairs, go to step 9 . If circuit is okay, go to next step.
Turn ignition off. Replace ECT sensor. After replacing sensor, go to step 9 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition off. Remove DOME fuse for 30 seconds (fuse located in passenger compartment fuse block). Reinstall DOME fuse. Reset radio clock time. Start engine. Operate vehicle within the conditions for running DTC or until DTC P0117 diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S17615892982001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Turn ignition on, with engine off. Using scan tool, observe stored information and Capture Info. If any undiagnosed DTCs are present, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no DTCs are present, system is okay.

Check for a damaged wiring harness. Check for a shifted ECT sensor. See appropriate SENSOR OPERATING RANGE CHARTS article. A shifted sensor could result in poor driveability complaints. After engine starts, ECT sensor value should increase steadily to about 203°F (95°C) and stabilize when thermostat opens. Ensure engine is not overheating and has not been subjected to overheating conditions (i.e., overload, trailer towing, hilly terrain, heavy stop and go traffic, etc.).

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, observe ECT sensor parameter on scan tool. If scan tool displays equal to or less than -40°F (-40°C), go to step 4. If scan tool display is not equal to or less than -40°F (-40°C), go to next step.
Using scan tool, clear DTC. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S30000368692001062700000).
Disconnect ECT sensor harness connector. Connect a fused jumper wire between ECT sensor harness connector terminals No. 1 (Orange/Black wire) and No. 3 (Blue/White wire) on 2.0L or terminals No. 1 (Orange/Black wire) and No. 3 (Gray/Yellow wire on 2.5L. see scheme 5 Observe ECT parameter on scan tool. If scan tool displays 329°F (165°C) on 2.0L, or 401°F (205°C) on 2.5L, go to step 6. If scan tool does not display 329°F (165°C) on 2.0L, or 401°F (205°C) on 2.5L, go to next step.
Connect a fused jumper wire between chassis ground and ECT sensor harness connector terminal No. 1 (Orange/Black wire). Observe ECT parameter on scan tool. If scan tool displays 329°F (165°C) on 2.0L, or 401°F (205°C) on 2.5L, go to step 7. If scan tool does not display 329°F (165°C) on 2.0L, or 401°F (205°C) on 2.5L, go to step 8.
Turn ignition off. Check for poor connection at ECT sensor. Repair as necessary. After repairs, go to step 12. If connection is okay, go to step 10.
Turn ignition off. Disconnect PCM harness connector C2. Check for open in Blue/White wire on 2.0L or Gray/Yellow wire on 2.5L between ECT sensor and ground circuit. Repair as necessary. After repairs, go to step 12. If circuit is okay, go to step 9.
Turn ignition off. Disconnect PCM harness connector C2. Check for an open in Orange/Black wire between ECT sensor and PCM. Repair as necessary. After repairs, go to step 12. If circuit is okay, go to next step.
Check for poor connections at ECT sensor and PCM connectors. Repair as necessary. After repairs, go to step 12. If connections are okay, go to step 11.
Replace ECT sensor. After replacing sensor, go to step 12.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
After repairs, clear DTCs. Operate vehicle within FREEZE FRAME conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000).

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Check if DTC P0122 or P0123 is set. If DTC P0122 or P0123 is also set, diagnose affected DTCs first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If DTC P0122 or P0123 is not set, go to next step.
Warm engine to normal operating temperature. Turn ignition on, with engine off. Using scan tool, observe TP sensor parameter on scan tool. If scan tool displays 0.2-1.0 volts with throttle at idle position and 3.4-4.7 volts with throttle at WOT, go to next step. If scan tool display is not 0.2-1.0 volts with throttle at idle position and 3.4-4.7 volts with throttle at WOT, go to step 5.
Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If this DTC resets, go to next step. If this DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S22223771662001062700000).
Turn ignition off. Disconnect TP sensor harness connector. Using DVOM, check resistance between TP sensor terminals No. 1 (Gray/Yellow wire) and No. 3 (Gray/Red wire) on 2.0L or terminals No. 1 (Gray/Red wire) and No. 3 (Gray/Yellow wire) on 2.5L. see scheme 6 If resistance is 4000-6000 ohms, go to next step. If resistance is not 4000-6000 ohms, go to step 8.
Ensure throttle plate is closed (at idle). Check resistance between TP sensor terminals No. 1 (Gray/Yellow wire) and No. 2 (Red/Green wire). If resistance is 500-1000 ohms, go to next step. If resistance is not 500-1000 ohms, go to step 8.
Connect DVOM between TP sensor terminals No. 1 (Gray/Yellow wire) and No. 2 (Red/Green wire) on 2.0L or terminals No. 2 (Red/Green wire) and No. 3 (Gray/Yellow wire) on 2.5L. Slowly move throttle from closed to open position while observing DVOM. If resistance changes smoothly from low to high while remaining within 500-6000 ohms, go to step 9. If resistance does not change smoothly from low to high while remaining within 500-6000 ohms, go to next step.
Replace TP sensor. After replacing sensor, go to step 11.
Check for high resistance, short to ground or short to voltage in Red/Green wire between TP sensor and PCM. Check for high resistance in Gray/Yellow wire between TP sensor and PCM. Check for poor connection at PCM. Repair as necessary. After repairs, go to step 11. If circuits and connection are okay, go to next step.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition off. Remove DOME fuse for 30 seconds (fuse is located in passenger compartment fuse block). Reinstall DOME fuse. Reset radio clock time. Start engine. Operate vehicle within the conditions for running DTC or until DTC P0121 diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S41127575372001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no DTCs are displayed, system is okay.

If DTC P0122 or P0123 is also set, diagnose those DTCs first. Check for a poor PCM electrical connection. Check for a damaged wiring harness. Check for a misadjusted TP sensor, or a binding or stuck throttle plate.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Warm engine to normal operating temperature. Using scan tool, observe TP sensor parameter while depressing throttle pedal from idle position to full throttle. If scan tool display steadily increases within range of 0-99 percent, go to next step. If scan tool display does not steadily increase within range of 0-99 percent, go to step 4.
Turn ignition on, with engine off. Using scan tool, clear DTC. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S15134446272001062700000).
Disconnect TP sensor harness connector. Connect a fused jumper wire between TP sensor harness connector terminals No. 2 (Red/Green wire) and No. 3 (Gray wire) on 2.0L or terminals No. 1 (Gray/Red wire) and No. 2 (Red/Green wire) on 2.5L. see scheme 6 Turn ignition on, with engine off. Observe TP sensor parameter on scan tool. If scan tool displays 99 percent, go to step 9. If scan tool does not display 99 percent, go to next step.
Connect a test light between battery voltage and TP sensor harness connector terminal No. 2 (Red/Green wire). Observe TP sensor parameter on scan tool. If scan tool displays 99 percent, go to next step. If scan tool does not display 99 percent, go to step 7.
Turn ignition off. Disconnect PCM harness connector C2. Check for open or short in Gray/Red wire between TP sensor and PCM. Repair as necessary. After repairs, go to step 12. If circuit is okay, go to step 8.
Check for open or short to ground in Red/Green wire between TP sensor and PCM. Repair as necessary. After repairs, go to step 12. If circuit is okay, go to next step.
Turn ignition off. Check for poor connection at PCM harness connector C2 terminal No. 9 on 2.0L or No. 12 on 2.5L. see scheme 3or see scheme 4. Repair as necessary. After repairs, go to step 12. If connection is okay, go to step 11.
Check for poor connections at circuits between TP sensor and PCM connectors. Repair as necessary. After repairs, go to step 12. If connection is okay, go to next step.
Turn ignition off. Replace TP sensor. After replacing sensor, go to step 12.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
After repairs, clear DTCs. Operate vehicle within FREEZE FRAME conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000).

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Warm engine to normal operating temperature. Using scan tool, observe TP sensor parameter while depressing throttle pedal from idle position to full throttle. If scan tool display steadily increases within range of 0-99 percent, go to step 4. If scan tool display does not steadily increase within range of 0-99 percent, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTC. Operate vehicle within FREEZE FRAME conditions. Recheck DTCs. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S28720150432001062700000).
Turn ignition off. Disconnect TP sensor harness connector. Turn ignition on, with engine off. Using DVOM, check voltage at TP sensor harness connector terminal No. 3 (Gray/Red wire) on 2.0L or No. 1 (Gray/Red wire) on 2.5L. If voltage reading is 5 volts, go to next step. If voltage reading is not 5 volts, go to step 8.
Using a test light connected to battery voltage, probe TP sensor harness connector terminal No. 1 (Gray/Yellow wire) on 2.0L or No. 3 (Gray/Yellow wire) on 2.5L. If test light illuminates, go to next step. If test light does not illuminate, go to step 10.
Turn ignition off. Reconnect TP sensor harness connector. Turn ignition on, with engine off. Using DVOM, backprobe PCM harness connector C2 terminal No. 9 (Red/Green wire) on 2.0L or terminal No. 12 (Red/Green wire) on 2.5L. see scheme 3or see scheme 4. If voltage reading is 0.5-1.0 volt, go to step 12. If voltage reading is not 0.5-1.0 volt, go to next step.
Turn ignition off. Disconnect PCM harness connector C2. Check for short to voltage in Red/Green wire between TP sensor and PCM. Repair as necessary. After repairs, go to step 13. If circuit is okay, go to step 9.
Turn ignition off. Disconnect PCM harness connector C2. Check for short to voltage in Gray/Red wire between TP sensor and PCM. Repair as necessary. After repairs, go to step 13. If circuit is okay, go to step 12.
Check for poor connection at TP sensor. Repair as necessary. After repairs, go to step 13. If connection is okay, go to step 11.
Turn ignition off. Check for an open in Gray/Yellow wire between PCM and TP sensor. Check TP sensor ground circuit for poor connection at PCM and TP sensor. Repair as necessary. After repairs, go to step 13. If circuit and connection are okay, go to step 12.
Replace TP sensor. After replacing sensor, go to step 13.
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition off. Remove DOME fuse for 30 seconds (fuse is located in passenger compartment fuse block). Reinstall DOME fuse. Reset radio clock time. Start engine. Operate vehicle within the conditions for running the DTC or until DTC P0123 diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S21742033442001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no DTCs are displayed, system is okay.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Turn ignition off. Allow engine to cool to ambient air temperature. Turn ignition on, with engine off. Compare ECT sensor parameter to IAT sensor parameter on scan tool. If both parameters are within 2-3° of each other, go to next step. If both parameters are not within 2-3° of each other, go to step 6 .
Start engine and immediately observe ECT sensor parameter on scan tool. Continue observing ECT for 10 minutes with engine at idle. If ECT indicated on scan tool increases to greater than 68°F (20°C) within 10 minutes, go to step 5 . If ECT indicated on scan tool does not increase to greater than 68°F (20°C) within 10 minutes, go to next step.
Retrieve DTCs. If any ECT related DTCs are set, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no ECT related DTCs are set, go to step 8 .
Fault is not present. Check for any other DTCs. Diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are set, see «DIAGNOSTIC AIDS»(ref-99188-S24323777592001062700000) .
Turn ignition off. Check ECT sensor resistance. Compare ECT sensor resistance with resistance values table. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article. If ECT sensor resistance is as specified, go to next step. If ECT sensor resistance is not as specified, go to step 9 .
Check for high resistance in ECT sensor circuits. Check for poor connections at PCM and ECT sensor. Repair as necessary. After repairs, go to step 11 . If circuit and connections are okay, go to step 10 .
Check coolant level or for proper operation of cooling system and thermostat. Repair as necessary. After repairs, go to step 11 .
Replace ECT sensor. After replacing sensor, go to step 11 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the conditions for running the DTC or until the DTC P0125 diagnostic has run. See «CODE ENABLE CRITERIA»(ref-99188-S32553131822001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no DTCs are displayed, system is okay.

If this DTC is set, ECT sensor may be skewed. Compare coolant temperature on scan tool display with actual engine coolant temperature measured with a thermometer. If displayed engine coolant temperature is not close to actual engine coolant temperature, replace ECT sensor. Check for a poor PCM electrical connection. Check for proper operation of thermostat.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, retrieve DTCs. If no HO2S related DTCs other than DTC P0131 and P0132 are set, go to next step. If any HO2S related DTCs other than DTC P0131 and P0132 are set, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000).
Start and warm engine to normal operating temperature. Increase engine speed to 2000 RPM for one minute. Using scan tool, observe HO2S No. 1 voltage. If voltage is switching to less than 300 millivolts or greater than 600 millivolts, go to next step. If voltage is not switching to less than 300 millivolts or greater than 600 millivolts, go to step 5.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Observe HO2S No. 1 parameter on scan tool. If scan tool displays voltage switching to less 300 millivolts or greater than 600 millivolts, see «DIAGNOSTIC AIDS»(ref-99188-S17748768312001062700000). If scan tool does not display voltage switching to less than 300 millivolts or greater than 600 millivolts, go to next step.
Disconnect HO2S No. 1 harness connector. Observe HO2S No. 1 parameter on scan tool. If scan tool displays 0-35 millivolts, go to next step. If scan tool does not display 0-35 millivolts, go to step 10.
Using a test light connected to battery voltage, probe HO2S No. 1 harness connector terminal No. 1 (White wire). see scheme 7 If test light illuminates, go to next step. If test light does not illuminate, go to step 8.
Using DVOM, select DC voltage scale. Connect one DVOM lead to battery voltage and other lead to HO2S No. 1 harness connector terminal No. 2 (Black/White wire). Observe HO2S No. 1 parameter on scan tool. If scan tool displays 1275 millivolts, go to step 11. If scan tool does not display 1275 millivolts, go to step 9.
Turn ignition off. Check for open in White wire between HO2S No. 1 and PCM. Repair as necessary. After repairs, go to step 13. If circuit is okay, go to step 12.
Turn ignition off. Check for an open or short in Black/White wire between HO2S No. 1 and PCM. Repair as necessary. After repairs, go to step 13. If circuit is okay, go to step 12.
Turn ignition off. Check for a short to voltage in Black/White wire between HO2S No. 1 and PCM. Repair as necessary. After repairs, go to step 13. If circuit is okay, go to step 12.
Replace HO2S No. 1. After replacing sensor, go to step 13.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition off. Remove DOME fuse for 30 seconds (located in passenger compartment fuse/relay block). Reinstall fuse. Reset radio clock time. Start engine and operate vehicle within the conditions for running DTC or until DTC P0131 diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S03676987582001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Turn ignition on, with engine off. Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no DTC are set, system is okay.

DTC will most likely set during city driving. Avoid operating vehicle on highway when validating DTC P0131. If DTCs other than P0171, P0172, P0300-P0304, P0400, and P0131-P0134 are set, diagnose those DTCs first. Check the following and repair as necessary

Misrouted HO2S No. 1 wiring contacting exhaust system.
Fuel pressure. If fuel pressure is too low, system can go lean setting DTC P0131.
Lean fuel injectors.
Vacuum leaks.
Exhaust leaks.
Shorted HO2S No. 1. If HO2S No. 1 is shorting to ground, scan tool display will be less than 0.1 volt.
Contaminated HO2S No. 1. Condition indicated by a powdery, White deposit on portion of HO2S No. 1 exposed to exhaust stream.
Fuel contamination.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, retrieve DTCs. If no HO2S related DTCs other than DTC P0131 and P0132 are set, go to next step. If any HO2S related DTCs other than DTC P0131 and P0132 are set, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000).
Start and warm engine to normal operating temperature. Increase engine speed to 2000 RPM for one minute. Using scan tool, observe HO2S No. 1 voltage. If voltage is switching to less than 300 millivolts or greater than 600 millivolts, go to next step. If voltage is not switching to less than 300 millivolts or greater than 600 millivolts, go to step 5.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions or until the applicable DTC diagnostic test has run. Increase engine speed to 2000 RPM for one minute. Observe HO2S No. 1 parameter on scan tool. If scan tool displays voltage switching to less 300 millivolts or greater than 600 millivolts, see «DIAGNOSTIC AIDS»(ref-99188-S31389629022001063000000). If scan tool does not display voltage switching to less than 300 millivolts or greater than 600 millivolts, go to next step.
Turn ignition off. Disconnect HO2S No. 1, bank 1 harness connector. Disconnect PCM harness connector C2. Turn ignition on, with engine off. Using a DVOM, check voltage between HO2S No. 1 harness connector terminals No. 1 (Gray/Yellow wire) and No. 2 (Red wire). see scheme 7 If voltage reading is zero volts, go to next step. If voltage reading is not zero volts, go to step 10.
Turn ignition off. Reconnect PCM harness connector C2. Turn ignition on, with engine off. Using a test light connected to battery voltage, probe HO2S harness connector terminal No. 1 (Gray/Yellow wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 8.
Connect DVOM between battery voltage and HO2S harness connector terminal No. 2 (Red wire). Start engine. Observe HO2S voltage parameter on scan tool. If voltage reading is 1000 millivolts, go to step 11. If voltage reading is not 1000 millivolts, go to step 9.
Check for open in Gray/Yellow wire between HO2S 1 and PCM. Repair as necessary. After repairs, go to step 13. If circuit is okay, go to step 12.
Check for open, short to ground or high resistance in Red wire between HO2S 1 and PCM. Repair as necessary. After repairs, go to step 13. If circuit is okay, go to step 12.
Turn ignition off. Repair short to voltage in Red wire between HO2S and PCM. After repairs, go to step 13.
Replace faulty HO2S. After replacing sensor, go to step 13.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for running DTC or until DTC diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S29327375012001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no DTCs are set, system is okay.

Misrouted HO2S No. 1 wiring contacting exhaust system.
Fuel pressure. If fuel pressure is too low, system can go lean setting DTC P0131.
Lean fuel injectors.
Vacuum leaks.
Exhaust leaks.
Shorted HO2S No. 1. If HO2S No. 1 is shorting to ground, scan tool display will be less than 0.1 volt.
Contaminated HO2S No. 1. Condition indicated by a powdery, White deposit on portion of HO2S No. 1 exposed to exhaust stream.
Fuel contamination.

Perform diagnostic system check. See «DIAGNOSTIC AIDS»(ref-99188-S01286741922001102200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Retrieve DTCs. If no HO2S related DTCs other than DTC P0131 and P0132 are set, go to next step. If any HO2S related DTCs other than DTC P0131 and P0132 are set, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000).
Warm engine to normal operating temperature. Increase engine speed to greater than 2000 RPM. Using scan tool, observe HO2S No. 1 parameter. If scan tool displays voltage switching to less than 300 millivolts or greater than 600 millivolts, go to next step. If scan tool does not display voltage switching to less than 300 millivolts or greater than 600 millivolts, go to step 5.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Observe HO2S No. 1 parameter on scan tool. If scan tool displays voltage switching to less than 300 millivolts or greater than 600 millivolts, see «DIAGNOSTIC AIDS»(ref-99188-S01286741922001102200000). If scan tool does not display voltage switching to less than 300 millivolts or greater than 600 millivolts, go to next step.
Turn ignition off. Disconnect HO2S No. 1 harness connector. Using a test light connected to battery voltage, probe HO2S No. 1 harness connector terminal No. (White wire). see scheme 7 If test light illuminates, go to next step. If test light does not illuminate, go to step 7.
Disconnect HO2S No. 1 harness connector. Observe HO2S 1 parameter on scan tool. If scan tool voltage reading is less than 100 millivolts, go to step 9. If scan tool voltage reading is not less than 100 millivolts, go to step 8.
Check for an open in White wire between HO2S No. 1 and PCM. Repair as necessary. After repairs, go to step 11. If circuit is okay, go to step 10.
Check for a short to voltage in Black/White wire between HO2S No. 1 and PCM. Repair as necessary. After repairs, go to step 11. If circuit is okay, go to step 10.
Replace HO2S No. 1. After replacing sensor, go to step 11.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition off. Remove DOME fuse for 30 seconds (located in passenger compartment fuse/relay block). Reinstall fuse. Reset radio clock time. Start engine and operate vehicle within the conditions for running DTC or until DTC P0132 diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S19314399692001102200000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no DTCs are set, system is okay.

DTC will most likely set during city driving. Avoid operating vehicle on highway when validating DTC P0132. If DTCs other than P0171, P0172, P0300-P0304, P0400, and P0131-P0134 are set, diagnose those DTCs first. Check the following and repair as necessary

Check HO2S No. 1 ground circuit for an open or short before replacing HO2S No. 1.
Fuel pressure. If fuel pressure is too high, system can go rich setting DTC P0132.
Check EVAP canister for fuel saturation.
Check for a leaking fuel pressure regulator diaphragm.
Shorted HO2S No. 1. If HO2S No. 1 is shorting to voltage, scan tool display will be greater than 1.0 volt.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, retrieve DTCs. If no HO2S related DTCs other than DTC P0131 and P0132 are set, go to next step. If any HO2S related DTCs other than DTC P0131 and P0132 are set, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000).
Warm engine to normal operating temperature. Increase engine speed to greater than 2000 RPM. Using scan tool, observe HO2S No. 1 parameter. If scan tool displays voltage switching to less than 300 millivolts or greater than 600 millivolts, go to next step. If scan tool does not display voltage switching to less than 300 millivolts or greater than 600 millivolts, go to step 5.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Observe HO2S No. 1 parameter on scan tool. If scan tool displays voltage switching to less than 300 millivolts or greater than 600 millivolts, see «DIAGNOSTIC AIDS»(ref-99188-S36202504302001062700000). If scan tool does not display voltage switching to less than 300 millivolts or greater than 600 millivolts, go to next step.
Turn ignition off. Disconnect HO2S No. 1 harness connector. Using a test light connected to battery voltage, probe HO2S No. 1 harness connector terminal No. 1 (Gray/Yellow wire). see scheme 7 If test light illuminates, go to next step. If test light does not illuminate, go to step 7.
Disconnect PCM harness connector C2. Turn ignition on, with engine off. Using a DVOM, check voltage between ground and PCM harness connector C2 terminal No. 4 (Red wire). see scheme 3or see scheme 4. If voltage reading is zero volts, go to step 9. If voltage reading is not zero volts, go to step 8.
Check for an open in Gray/Yellow wire between HO2S No. 1 and PCM. Repair as necessary. After repairs, go to step 11. If circuit is okay, go to step 10.
Check for a short to voltage in Red wire between HO2S No. 1 and PCM. Repair as necessary. After repairs, go to step 11. If circuit is okay, go to step 10.
Replace HO2S No. 1. After replacing sensor, go to step 11.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within conditions for running the DTC or until the DTC diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S20329609012001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, go «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no DTCs are set, system is okay.

Check HO2S No. 1 ground circuit for an open or short before replacing HO2S No. 1.
Fuel pressure. If fuel pressure is too high, system can go rich setting DTC P0132.
Check EVAP canister for fuel saturation.
Check for a leaking fuel pressure regulator diaphragm.
Shorted HO2S No. 1. If HO2S No. 1 is shorting to voltage, scan tool display will be greater than one volt.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If only DTC P0133 is set, go to next step. If any other DTC is set, diagnose DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) .
Visually and physically inspect HO2S No 1 for proper installation, corrosion of harness connectors, proper connection at PCM and HO2S No. 1 harness connectors, damaged wiring harness, or contaminated sensor. Repair as necessary. After repairs, go to step 6 . If no problem is found, go to next step.
Check for exhaust leak near engine. If exhaust leak exists, go to step 6 . If no exhaust leak is found, go to next step.
Replace HO2S No. 1. After replacing sensor, go to step 7 .
Turn ignition off. Repair as necessary. After repairs, turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within conditions for running the DTC. See «CODE ENABLE CRITERIA»(ref-99188-S36654292922001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no DTCs are set, system is okay.

DTC will most likely set during city driving. Avoid operating vehicle on highway when validating DTC P0133. If DTCs other than P0171, P0172, P0300-P0304, P0400, and P0131-P0134 are set, diagnose those DTCs first. Check for a damaged wiring harness.

Perform diagnostic system check. See «DIAGNOSTIC AIDS»(ref-99188-S15481485882001102200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If only DTC P0133 is set, go to next step. If any other DTC is set, diagnose DTCs.
Turn ignition off. Visually and physically inspect HO2S No 1 for proper installation, corrosion of harness connectors, proper connection at PCM and HO2S No. 1 harness connectors, damaged wiring harness, or contaminated sensor. Repair as necessary. After repairs, go to step 6 . If no problem is found, go to next step.
Check for exhaust leak near engine. If exhaust leak exists, go to step 6 . If no exhaust leak is found, go to next step.
Replace HO2S No. 1. After replacing sensor, go to step 7 .
Repair exhaust leak as necessary. After repairs, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for running the DTC or until DTC diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S06870040612001102200000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no DTCs are displayed, system is okay.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, retrieve DTCs. If only DTC P0131, P0132, P0133, P0136, P0171 and P0172 are set, go to next step. If any other DTC is set, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000).
Start and warm engine to normal operating temperature. Operate engine at greater than 2000 RPM for one minute. Operate vehicle within conditions for setting DTC. See «CODE ENABLE CRITERIA»(ref-99188-S02280989322001101800000). Using scan tool, monitor HO2S 1 voltage parameter. If scan tool displays voltage switching to less than 300 millivolts or greater than 600 millivolts, go to next step. If scan tool does not display voltage switching to less than 300 millivolts or greater than 600 millivolts, go to step 5.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Observe HO2S No. 1 parameter on scan tool. If scan tool display remains within 300-600 millivolts, go to next step. If scan tool display does not remain within 300-600 millivolts, see «DIAGNOSTIC AIDS»(ref-99188-S36778415012001062700000).
Disconnect HO2S No. 1 harness connector. Observe HO2S No. 1 parameter on scan tool. If scan tool displays 0-35 millivolts, go to next step. If scan tool does not display 0-35 millivolts, go to step 10.
Using a test light connected to battery voltage, probe HO2S No. 1 harness connector terminal No. 2 (Red wire). see scheme 7 If test light illuminates, go to next step. If test light does not illuminate, go to step 8.
Using DVOM, select DC voltage scale on DVOM. Connect one DVOM lead to battery voltage and the other lead to HO2S No. 1 harness connector terminal No. 2 (Red wire). Observe HO2S No. 1 parameter on scan tool. If scan tool displays 1275 millivolts, go to step 11. If scan tool does not display 1275 millivolts, go to step 9.
Turn ignition off. Check for open in Gray/Yellow wire between HO2S No. 1 and PCM. Repair as necessary. After repairs, go to step 13. If circuit is okay, go to step 12.
Turn ignition off. Check for open or short to ground in Red wire between HO2S No. 1 and PCM. Repair as necessary. After repairs, go to step 13. If circuit is okay, go to step 12.
Turn ignition off. Check for short to voltage in Red wire between HO2S No. 1 and PCM. Repair as necessary. After repairs, go to step 13. If circuit is okay, go to step 12.
Turn ignition off. Replace HO2S No. 1. After replacing sensor, go to step 13.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within conditions for running this DTC. See «CODE ENABLE CRITERIA»(ref-99188-S02280989322001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If not DTCs are displayed, system is okay.

If DTCs other than P0171, P0172, P0300-P0304, P0400, and P0131-P0134 are set, diagnose those DTCs first. Check the following and repair as necessary

Vacuum leaks.
Exhaust leaks.
Fuel pressure. If fuel pressure is too high or low, system can go rich or lean setting DTC.
Check EVAP canister for fuel saturation.
Check for a leaking fuel pressure regulator diaphragm.
Contaminated HO2S No. 1.
Check for a poor electrical connection at PCM.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
If any other DTCs are set other than fuel trim and HO2S DTCs, see «DIAGNOSTIC AIDS»(ref-99188-S21535349872001070200000). If no other DTCs are set, go to next step.
Warm engine to normal operating temperature. Operate engine at greater than 2000 RPM for one minute. Operate vehicle under conditions for setting DTC. See «CODE ENABLE CRITERIA»(ref-99188-S12020634232001101800000). Using scan tool, observe HO2S No. 1 parameter. If scan tool displays voltage switching to less than 300 millivolts or greater than 600 millivolts, go to next step. If scan tool does not display voltage switching to less than 300 millivolts or greater than 600 millivolts, go to step 5.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Observe HO2S No. 1 parameter on scan tool. If scan tool display remains within 300-600 millivolts, go to next step. If scan tool display does not remain within 300-600 millivolts, see «DIAGNOSTIC AIDS»(ref-99188-S21535349872001070200000).
Turn ignition off. Disconnect HO2S 1, bank 1 harness connector. Disconnect PCM harness connector C2. Turn ignition on, with engine off. Using a DVOM, check voltage between ground and HO2S 1 harness connector terminal No. 2 (Red wire). see scheme 7 If voltage reading is zero volts, go to next step. If voltage reading is not zero volts, go to step 10.
Turn ignition off. Reconnect PCM harness connector. Turn ignition on, with engine off. Using a test light connected to battery voltage, probe HO2S harness connector terminal No. 1 (Gray/Yellow wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 8.
Using a DVOM, select DC voltage scale. Connect one DVOM lead to battery voltage and the other lead to HO2S No. 1 harness connector terminal No. 2 (Red wire). Start engine. Observe HO2S No. 1 parameter on scan tool. If scan tool displays 1000 millivolts, go to step 11. If scan tool does not display 1000 millivolts, go to step 9.
Turn ignition off. Check for an open in Gray/Yellow wire between HO2S No. 1 and PCM. Repair as necessary. After repairs, go to step 13. If circuit is okay, go to step 12.
Turn ignition off. Check for open or short to ground in Red wire between HO2S No. 1 and PCM. Repair as necessary. After repairs, go to step 13. If circuit is okay, go to step 12.
Turn ignition off. Check for short to voltage in Red wire between HO2S No. 1 and PCM. Repair as necessary. After repairs, go to step 13. If circuit is okay, go to step 12.
Turn ignition off. Replace HO2S No. 1. After replacing sensor, go to step 13.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn on, with engine off. Using scan tool, clear DTCs. Start engine and operate vehicle within conditions for running the DTC. See «CODE ENABLE CRITERIA»(ref-99188-S12020634232001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs. Diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no DTC are displayed, system is okay.

If DTCs other than P0171, P0172, P0300-P0304, P0400, and P0131-P0134 are set, diagnose those DTCs first. Check the following and repair as necessary

Vacuum leaks.
Exhaust leaks.
Fuel pressure. If fuel pressure is too high or low, system can go rich or lean setting DTC.
Check EVAP canister for fuel saturation.
Check for a leaking fuel pressure regulator diaphragm.
Contaminated HO2S No. 1.
Check for a poor electrical connection at PCM.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Turn ignition off. Disconnect HO2S 1 harness connector. Turn ignition on, with engine off. Using a test light connected to ground, probe HO2S 1 harness connector terminal No. 4 (Black/White wire). see scheme 7 If test light illuminates, go to next step. If test light does not illuminate, go to step 7.
Turn ignition off. Using a DVOM, check resistance between HO2S 1 harness connector terminals No. 3 (Black/White wire) and No. 4 (Gray wire). Resistance should be 4.5-5.7 ohms at 68°F (20°C ) on HO2S with warm-up TWC or 11.7-15.6 ohms at 68°F (20°C ) on HO2S without warm-up TWC. If resistance is as specified, go to next step. If resistance is not as specified, go to step 8.
Connect test light between battery voltage and HO2S harness connector terminal No. 3 (Gray wire). Start engine. If test light illuminates only when engine is running, see «DIAGNOSTIC AIDS»(ref-99188-S00915511042001062700000). If test light does not illuminate when engine is running, go to next step.
Turn ignition off. Reconnect HO2S harness connector. Disconnect PCM harness connector C2. Turn ignition on, with engine off. Check voltage at PCM harness connector C2 terminal No. 4 (Gray wire). see scheme 3or see scheme 4. If voltage reading is greater than 10 volts, go to step 10. If voltage reading is not greater than 10 volts, go to next step.
Turn ignition off. Repair open or short to ground in Gray wire between HO2S 1 and PCM. After repairs, go to step 11.
Turn ignition off. Repair open in Black/White wire between HO2S 1 and fuse block. After repairs, go to step 11.
Check for faulty connection at HO2S 1 harness connector. Repair as necessary. After repairs, go to step 11. If connection is okay, go to next step.
Replace HO2S 1. After replacing sensor, go to step 11.
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within FREEZE FRAME conditions or until HO2S heater diagnostic has run. If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnosed affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no DTC are displayed, system is okay.

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Check harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, check for HO2S heater circuit performance DTCs P0135, P0141, P0155 or P0161. If one or more of these DTCs are present, go to step 7. If these DTCs are not present, go to next step.
Turn ignition off. Disconnect HO2S harness connector. Turn ignition on, with engine off. Using a test light connected ground, probe HO2S harness connector terminal No. 4 (Blue wire). see scheme 7 If test light illuminates, go to next step. If test light does not illuminate, go to step 7.
Turn ignition off. Disconnect HO2S harness connector. Check resistance between HO2S harness connector terminals No. 3 (Gray wire) and No. 4 (Blue wire). If resistance is 3.0-3.6 ohms at 68°F (20°C), go to next step. If resistance is not 3.0-3.6 ohms at 68°F (20°C), go to step 19.
Connect test light between battery voltage and HO2S 1 harness connector terminal No. 3 (Gray wire). Start engine. If test light illuminates only when engine is running, see «DIAGNOSTIC AIDS»(ref-99188-S10426876062001070200000). If test light does not illuminate when engine is running, go to next step.
Turn ignition off. Reconnect HO2S harness connector. Disconnect PCM harness connector C2. Turn ignition on, with engine off. Check voltage at PCM harness connector C2 terminal No. 6 (Gray wire). see scheme 3or see scheme 4. If voltage is greater than 10 volts, go to step 20. If voltage is not greater than 10 volts, go to step 16.
Turn ignition off. Check IG fuse (located in passenger compartment fuse/relay block). If fuse is open, go to step 14. If fuse if okay, go to next step.
Disconnect HO2S relay from wiring harness (relay is located rear of windshield washer reservoir, on left inner fender). Turn ignition on, with engine off. Using a test light connected to ground, probe relay harness connector terminal No. 1 (Blue/White wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 11.
Using test light connected to ground, probe HO2S relay harness connector terminal No. 3 (Black/White wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 13.
Turn ignition off. Using test light connected to battery voltage, probe HO2S relay harness connector terminal No. 4 (Black wire). If test light illuminates, go to step 17. If test light does not illuminate, go to step 12.
Turn ignition off. Repair open in Black/White wire between IG fuse and HO2S relay. After repairs, go to step 22.
Turn ignition off. Check for open or poor connection in Black wire between HO2S relay and ground connector Repair as necessary. After repairs, go to step 22.
Turn ignition off. Repair open in Black/White wire between IG fuse and HO2S relay. After repairs, go to step 22.
Check for short to ground in Black/White wire between IG fuse and HO2S relay. Repair as necessary. After repairs, go to step 22. If circuit is okay, go to next step.
Replace faulty HO2S. After replacing sensor, go to step 22.
Turn ignition off. Repair open or short to ground in Gray wire between HO2S 1 and PCM. After repairs, go to step 22.
Check for open in Blue wire between HO2S relay and HO2S 1 or check for poor connection at HO2S relay and HO2S 1. Repair as necessary. After repairs, go to step 22. If circuit is okay, go to next step.
Replace HO2S relay. After replacing relay, go to step 22.
Replace HO2S. After replacing sensor, go to step 22.
Turn ignition off. Check for faulty connection at HO2S harness connector. Repair as necessary. After repairs, go to step 22. If connection is okay, go to next step.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition off. Remove DOME fuse for 30 seconds (located in passenger compartment fuse/relay block). Reinstall fuse. Reset radio clock time. Start engine and operate vehicle within the conditions for running the DTC or until DTC P0135 or DTC P0155 diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S08568214542001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Turn ignition on, with engine off. Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no DTCs are displayed, system is okay.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Allow engine cool down for 2 minutes. Turn ignition on, with engine off. Using scan tool, observe HO2S No. 2 voltage parameter. Warm engine to normal operating temperature. ECT should be 176°F (80°C). Operate engine at 2000 RPM for an additional 5 minutes, while continuing to observe HO2S No. 2 voltage. If HO2S No. 2 voltage starts at less than 100 millivolts, then increase to greater than 100 millivolts as engine is warmed, go to next step. If HO2S No. 2 voltage does not start at less than 100 millivolts, nor increase to greater than 100 millivolts as engine is warmed, go to step 4.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S04334360642001062700000).
Using DVOM, select millivolt DC scale. Connect one DVOM lead to battery voltage and the other lead to HO2S No. 2 harness connector terminal No. 2 (Red/Green wire). see scheme 7 Observe HO2S No. 2 voltage parameter on scan tool. If scan tool voltage reading is 1275 millivolts, go to next step. If scan tool voltage reading is not 1275 millivolts, go to step 8.
Observe HO2S No. 2 parameter on scan tool. Using a jumper wire connected to ground, jumper HO2S No. 2 harness connector terminal No. 2 (Red/Green wire). If voltage reading is less than 55 millivolts, go to next step. If voltage reading is not less than 55 millivolts, go to step 10.
Turn ignition on, with engine off. Using a test light connected to battery voltage, probe HO2S No. 2 harness connector terminal No. 1 (Gray/Yellow wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 9.
Turn ignition off. Replace HO2S No. 2. After replacing sensor, go to step 11.
Turn ignition off. Check for open or short in Red/Green wire between HO2S 2 and PCM, or check for poor connections at HO2S 2 and PCM connectors. Repair as necessary. After repairs, go to step 11. If circuit or connections are okay, go to step 10.
Turn ignition off. Check for open in Gray/Yellow wire between HO2S 2 and PCM connectors. Repair as necessary. After repairs, go to step 11. If circuit or connections are okay, go to next step.
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for running the DTC. See «CODE ENABLE CRITERIA»(ref-99188-S38409703902001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Turn ignition on, with engine off. Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no DTCs are displayed, system is okay.

Check the following and repair as necessary

Exhaust system for leaks.
Misrouted HO2S No. 2 wiring.
HO2S No. 2 for physical damage.
Shorted HO2S No. 2.
Poor HO2S No. 2 connection at PCM.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, observe HO2S No. 2 voltage display on scan tool. Start and warm engine to normal operating temperature, then operate engine at 2000 RPM for an additional 5 minutes while observing HO2S No. 2 voltage. Allow engine to return to idle. Observe scan tool while briefly accelerating engine several times, then allowing engine to return to idle between each acceleration. If HO2S No. 2 voltage start at greater than 800 millivolts, then decrease to a fluctuating voltage when accelerating engine, go to next step. If HO2S No. 2 voltage does not start at greater than 800 millivolts, then decrease to a fluctuating voltage when accelerating engine, go to step 4.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S37477746932001070200000).
Turn ignition off. Disconnect HO2S 2, bank 1 harness connector. Disconnect PCM harness connector C2. Turn ignition on, with engine off. Connect a DVOM between ground to HO2S 2 harness connector terminal No. 2 (Blue wire). see scheme 7 If voltage reading is zero volts, go to next step. If voltage reading is not zero volts, go to step 10.
Turn ignition off. Reconnect PCM harness connector. Turn ignition on, with engine off. Using a DVOM, check voltage between battery voltage and HO2S No. 2 harness connector terminal No. 2 (Blue wire). Start engine. Observe HO2S No. 2 voltage parameter on scan tool. If voltage reading is 1275 millivolts, go to next step. If voltage reading is not 1275 millivolts, go to step 8.
Turn ignition on, with engine off. Using a test light connected to battery voltage, probe HO2S 2 harness connector terminal No. 1 (Yellow wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 9.
Turn ignition off. Replace HO2S 2. After replacing sensor, go to step 12.
Turn ignition off. Check for open, short to ground, or high circuit resistance in Blue wire between HO2S 2 and PCM. Repair as necessary. After repairs, go to step 12. If circuit is okay, go to step 11.
Turn ignition off. Check for open or faulty connection in Yellow wire between HO2S 2 and ground circuit or PCM. Repair as necessary. After repairs, go to step 12. If connection is okay, go to step 11.
Turn ignition off. Repair short to voltage in Blue wire. After repairs, go to step 12.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for running the DTC. See «CODE ENABLE CRITERIA»(ref-99188-S38409703902001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Turn ignition on, with engine off. Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no DTCs are displayed, system is okay.

Check the following and repair as necessary

Exhaust system for leaks.
Misrouted HO2S No. 2 wiring.
HO2S No. 2 for physical damage.
Shorted HO2S No. 2.
Poor HO2S No. 2 connection at PCM.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Turn ignition off. Disconnect HO2S 2 harness connector. Turn ignition on, with engine off. Using a test light connected to ground, probe HO2S 2 harness connector terminal No. 4 (Black/White wire). see scheme 7 If test light illuminates, go to next step. If test light does not illuminate, go to step 6.
Using a DVOM, check resistance between HO2S 2 harness connector terminals No. 3 (Pink/Green wire) and No. 4 (Black/White wire). If HO2S heater resistance is 11.7-15.6 ohms at 68°F (20°C), go to next step. If HO2S heater resistance is not 11.7-15.6 ohms at 68°F (20°C), go to step 7.
Turn ignition off. Reconnect HO2S harness connector. Disconnect PCM harness connector C1. Turn ignition on, with engine off. Check voltage at PCM harness connector C1 terminal No. 3 (Pink/Green wire). see scheme 3or see scheme 4. If voltage reading is greater than 10 volts, go to step 9. If voltage reading is not greater than 10 volts, go to next step.
Turn ignition off. Repair open or short to ground in Pink/Green wire. After repairs, go to step 10.
Turn ignition off. Repair open in Black/White wire. After repairs, go to step 10.
Turn ignition off. Check for a faulty connection at HO2S 2 harness connector. Repair as necessary. After repairs, go to step 10. If connection is okay, go to next step.
Replace HO2S 2. After replacing sensor, go to step 10.
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the FREEZE FRAME conditions or until HO2S heater diagnostic has run. If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Turn ignition on, with engine off. Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no DTCs are displayed, system is okay.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using a scan tool, check for HO2S heater circuit performance DTCs P0135, P0141, P0155 or P0161. If one or more of these DTCs are set, go to step 7. If these DTCs not set, go to next step.
Turn ignition off. Disconnect HO2S 2 harness connector. Turn ignition on, with engine off. Using a test light connected to ground, probe HO2S 2 harness connector terminal No. 4 (Blue wire). see scheme 7 If test light illuminates, go to next step. If test light does not illuminate, go to step 7.
Turn ignition off. Check resistance between HO2S 2 harness connector terminals No. 3 (White/Black wire) and No. 4 (Blue wire). If resistance 5.0-7.0 ohms at 68°F (20°C), go to next step. If resistance is not 5.0-7.0 ohms at 68°F (20°C), go to step 19.
Reconnect HO2S 2 harness connector. Disconnect PCM harness connector C2. Turn ignition on, with engine off. Using a DVOM, check voltage at PCM harness connector C2 terminal No. 17 (White/Black wire). see scheme 3or see scheme 4. If voltage reading is greater than 10 volts, go to next step. If voltage reading is not greater than 10 volts, go to step 16.
Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions or until this DTC test has run. If DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S18438707152001070200000). If DTC resets, go to step 20.
Turn ignition off. Check HO2S fuse (located above passenger compartment fuse/relay block). If fuse is open, go to step 14. If fuse is okay, go to next step.
Disconnect HO2S 2 relay from wiring harness (relay is located on rear of windshield washer reservoir, on left inner fender). Turn ignition on, with engine off. Using a test light connected to ground, probe HO2S relay terminal No. 1 (Blue/White wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 11.
Using test light connected to ground, probe HO2S relay harness connector terminal No. 3 (Black/White wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 13.
Using test light connected to battery voltage, probe HO2S relay harness connector terminal No. 4 (Black wire). If test light illuminates, go to step 17. If test light does not illuminate, go to step 12.
Turn ignition off. Repair open in Black/White wire between IG fuse and HO2S relay. After repairs, go to step 22.
Turn ignition off. Check for open or poor connection in Black wire between HO2S relay and ground connector. Repair as necessary. After repairs, go to step 22.
Turn ignition off. Repair open in Black/White wire between IG fuse and HO2S relay. After repairs, go to step 22.
Check for short to ground in Blue/White wire between HO2S relay fuse and HO2S relay. Repair as necessary. After repairs, go to step 22. If circuit is okay, go to next step.
Replace faulty HO2S. After replacing sensor, go to step 22.
Turn ignition off. Repair open or short to ground in White/Black wire between HO2S 2 and PCM. After repairs, go to step 22.
Turn ignition off. Check for open or poor connection in Blue wire between HO2S relay terminal No. 2 and HO2S 2. Repair as necessary. After repairs, go to step 22. If circuit or connection is okay, go to next step.
Replace HO2S relay. After replacing relay, go to step 22.
Replace HO2S. After replacing sensor, go to step 22.
Turn ignition off. Check for faulty connection at HO2S harness connector. Repair as necessary. After repairs, go to step 22. If connection is okay, go to next step.
Replace the PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for running this DTC or until DTC diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S00235458792001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Turn ignition on, with engine off. Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no DTCs are displayed, system is okay.

Check HO2S relay resistance. Resistance across terminals No. 3 and 4 should be 79-95 ohms at 68°F (20°C). Resistance across terminals No. 1 and 2 should be infinite. Check for a poor PCM connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Check harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, check for HO2S heater circuit performance DTCs P0135, P0141, P0155 or P0161. If any of these DTCs are set, go to step 7. If these DTCs are not set, go to next step.
Turn ignition off. Disconnect HO2S 2, bank 2 harness connector. Turn ignition on, with engine off. Using a test light connected to ground, probe HO2S 2 harness connector terminal No. 4 (Blue wire). see scheme 7 If test light illuminates, go to next step. If test light does not illuminate, go to step 7.
Turn ignition off. Using a DVOM, check resistance between HO2S 2 harness connector terminals No. 3 (Pink/White wire) and No. 4 (Blue wire). If resistance is 5.0-7.0 ohms at 68°F (20°C), go to next step. If resistance is not 5.0-7.0 ohms at 68°F (20°C), go to step 19.
Reconnect HO2S harness connector. Disconnect PCM harness connector C2. Turn ignition on, with engine off. Check voltage at PCM harness connector C2 terminal No. 16 (Pink/White wire). If voltage reading is greater than 10 volts, go to next step. If voltage reading is not greater than 10 volts, go to step 16.
Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions or until this DTC test has run. If DTC P0141 does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S42407678832001070200000). If DTC P0141 resets, go to step 20.
Turn ignition off. Check HO2S fuse (located above passenger compartment fuse/relay block). If fuse is open, go to step 14. If fuse is okay, go to next step.
Disconnect HO2S relay from wiring harness (relay is located rear of windshield washer reservoir, mounted in left inner fender). Turn ignition on, with engine off. Using a test light connected to ground, probe HO2S relay harness connector terminal No. 1 (Blue/White wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 11.
Using test light connected to ground, probe HO2S relay harness connector terminal No. 3 (Black/White wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 13.
Turn ignition off. Using test light connected to battery voltage, probe HO2S harness connector terminal No. 4 (Black wire). If test light illuminates, go to step 17. If test light does not illuminate, go to step 12.
Turn ignition off. Repair open in Black/White wire between IG fuse and HO2S relay. After repairs, go to step 22.
Check for open or poor connection in Black wire between HO2S relay and ground terminal. Repair as necessary. After repairs, go to step 22.
Turn ignition off. Repair open in Black/White wire between IG fuse and HO2S relay. After repairs, go to step 22.
Check for short to ground in Blue/White wire between HO2S relay and HO2S fuse. Repair as necessary. After repairs, go to step 22. If circuit is okay, go to next step.
Replace faulty HO2S. After replacing sensor, go to step 22.
Turn ignition off. Repair open or short to ground in Pink/White wire between HO2S 2 and PCM. After repairs, go to step 22.
Repair open or short to ground in Pink/White wire between HO2S 2 and PCM. After repairs, go to step 22.
Replace HO2S relay. After replacing relay, go to step 22.
Replace HO2S. After replacing sensor, go to step 22.
Turn ignition off. Check for faulty connection at HO2S harness connector. Repair as necessary. After repairs, go to step 22. If connection is okay, go to next step.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for running this DTC or until DTC diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S35990917912001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Turn ignition on, with engine off. Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no DTCs are displayed, system is okay.

Check HO2S relay resistance. Resistance across terminals No. 3 and 4 should be 79-95 ohms at 68°F (20°C). Resistance across terminals No. 1 and 2 should be infinite. Check for a poor PCM connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside insulation. Check harness connectors for backed-out terminal, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before replacing component.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Start engine. Operate vehicle while loop status indicates CLOSED LOOP. Using scan tool, observe short term fuel trim parameter. If scan tool displays 15 percent, go to next step. If scan tool does not display 15 percent, go to step 4 .
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions Observe total fuel trim parameter on scan tool. If scan tool displays less than 43 percent, go to «DIAGNOSTIC AIDS»(ref-99188-S36206998072001062700000) . If scan tool displays greater than 43 percent, go to next step.
Turn ignition off. Visually and physically check the following items: Vacuum hoses for splits, kinks and improper connections. PCV valve for proper installation. Exhaust system for leaks near HO2S. EVAP control system for proper operation. Repair as necessary. After repairs, go to step 11 . If problem is found, go to next step.
Start and warm engine to normal operating temperature. Using scan tool, observe operation of MAP, ECT and TP sensors at idle. Compare sensor readings with scan tool typical data values. Check vehicle for cause of any erratic readings. Repair as necessary. After repairs, go to step 11 . If no problem is found, go to next step.
Turn ignition off. Install fuel pressure gauge. Start engine. Warm engine to normal operating temperature. Observe fuel pressure at an idle. If fuel pressure is 36-43 psi (2.5-3.0 kg/cm 2 ), go to next step. If fuel pressure is not 36-43 psi (2.5-3.0 kg/cm 2 ), diagnose fuel system as necessary. See FUEL SYSTEMS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
Check fuel for excessive water, alcohol or other contaminates. If fuel is contaminated, go to next step. If fuel is not contaminated, go to step 9 .
Turn ignition off. Replace contaminated fuel. After repairs, go to step 11 .
Check fuel injectors for regular and even fuel discharge, and fuel dispersed in a conical spray pattern. Ensure injector coil resistance is within specification. See FUEL SYSTEM in appropriate BASIC DIAGNOSTIC PROCEDURES article. If problem(s) exists, go to next step. If no problems exist, go to «DIAGNOSTIC AIDS»(ref-99188-S36206998072001062700000) .
Replace faulty fuel injectors. After repairs, go to next step.
Turn ignition off. Remove DOME fuse for 30 seconds (fuse is located in passenger compartment fuse block). Reinstall DOME fuse. Reset radio clock time. Start engine. Operate vehicle within the conditions for running the DTC or until DTC P0171 diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S19767825662001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no DTCs are displayed, system is okay.

Check the following and repair as necessary

Vacuum leaks.
Exhaust leaks.
Correct fuel pressure. Fuel pressure while driving vehicle under different conditions. If fuel pressure is too low, system can go lean setting DTC P0171.
Fuel contamination.
Malfunctioning MAF sensor.
Damaged wiring harness.
Contaminated HO2S.
HO2S No. 1 for water intrusion.
Poor HO2S No. 1 and MAF sensor connections at PCM.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Start and warm engine to normal operating temperature. Operate vehicle until scan tool indicates CLOSED LOOP. Observe short term FT parameter on scan tool. If scan tool displays less than 15 percent, go to next step. If scan tool does not display less than 15 percent, go to step 4 .
Turn ignition on, with engine off. Using scan tool, clear DTC information function. Operate vehicle within FREEZE FRAME conditions that set DTC. Observe the total fuel trim parameter on scan tool. If scan tool displays less than 33 percent, see «DIAGNOSTIC AIDS»(ref-99188-S03636568092001070200000) . If scan tool does not display less than 33 percent, go to next step.
Turn ignition off. Visually and physically check for any splits, kinks, and improper connections in vacuum hoses. Check for proper PCV valve operation. Check for exhaust system leaks near the HO2S. Check for correct operation of EVAP control system. Repair as necessary. If a problem is found, go to step 11 . If no problem is found, go to next step.
Start and warm engine to normal operating temperatures. Operate engine at idle. Using scan tool, observe operation of MAP, ECT and TP sensors. Compare the observed sensor readings with the typical scan tool data values. See appropriate PIDS VALUE CHARTS article. Repair as necessary. After repairs, go to step 11 . If no problem is found, go to next step.
Turn ignition off. Install Fuel Pressure Gage (J-34730-1A). Start engine. Observe fuel pressure with engine idling at normal operating temperatures. If fuel pressure is 39-45 psi (270-310 kPa), go to next step. If fuel pressure is not 39-45 psi (270-310 kPa), diagnose fuel system.
Turn ignition off. Check fuel for excessive water, alcohol or other contaminants. If contamination is found, go to next step. If no contamination is found, go to step 9 .
Replace any contaminated fuel. After replacing fuel, go to step 11 .
Check fuel injectors for even and normal discharge. Fuel should be dispersed in a conical spray pattern. Check fuel injector resistance. See appropriate SYSTEM & COMPONENT TESTING article. If no problem is found, see «DIAGNOSTIC AIDS»(ref-99188-S03636568092001070200000) . If problem is found, go to next step.
Replace faulty fuel injectors. After repairs, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for running this DTC or until DTC diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S27211731822001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Turn ignition on, with engine off. Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no DTCs are displayed, system is okay.

Check the following and repair as necessary

Vacuum leaks.
Exhaust leaks.
Correct fuel pressure. Check fuel pressure while driving vehicle under different conditions. If fuel pressure is too low, system can go lean setting DTC.
Fuel contamination.
Malfunctioning MAF sensor.
Damaged wiring harness.
Contaminated HO2S.
HO2S No. 1 for water intrusion.
Poor HO2S No. 1 and MAF sensor connections at PCM.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Operate vehicle while loop status indicates CLOSED LOOP on scan tool. Observe short term fuel trim parameter on scan tool. If scan tool displays greater than -11 percent, go to next step. If scan tool displays less than -11 percent, go to step 4 .
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Observe total fuel trim parameter on scan tool. If scan tool displays -30 percent or greater, go to «DIAGNOSTIC AIDS»(ref-99188-S03019088482001062700000) . If scan tool does not display -30 percent or greater, go to next step.
Visually and physically check air intake system for restrictions. Repair as necessary. After repairs, go to step 10 . If no problems exist, go to next step.
Turn ignition off. Install fuel pressure gauge. Start engine. Warm engine to normal operating temperature. Observe fuel pressure at an idle. If fuel pressure is 36-43 psi (2.5-3.0 kg/cm 2 ), go to next step. If fuel pressure is not 36-43 psi (2.5-3.0 kg/cm 2 ), diagnose fuel system as necessary. See FUEL SYSTEMS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
Check EVAP system for possible over purging of fuel vapors. Repair as necessary. After repairs, go to step 10 . If no problems exist, go to next step.
Turn ignition off. Remove HO2S No. 1. Check HO2S No. 1 for damage or contamination. Replace as necessary. After repairs, go to step 10 . If HO2S No. 1 is not damaged or contaminated, go to next step.
Check fuel injectors for regular and even fuel discharge, fuel leaking from ball valve of injector, and fuel dispersed in a conical spray pattern. Ensure injector coil resistance is within specification. See FUEL SYSTEMS in appropriate BASIC DIAGNOSTIC PROCEDURES article. If problem(s) exists, go to next step. If no problems exist, go to «DIAGNOSTIC AIDS»(ref-99188-S03019088482001062700000) .
Replace faulty fuel injectors. After repairs, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the conditions for running the DTC. See «CODE ENABLE CRITERIA»(ref-99188-S38933150612001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Turn ignition on, with engine off. Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no DTCs are displayed, system is okay.

If DTCs other than P0171, P0172, P0300-P0304 and P0400 are set, diagnose those DTCs first. Check the following and repair as necessary

Restriction in inlet air passage.
Correct fuel pressure. Fuel pressure while driving vehicle under different conditions. If fuel pressure is too high, system can go rich setting DTC P0172.
Malfunctioning MAF sensor.
Damaged wiring harness.
Contaminated HO2S.
HO2S No. 1 for water intrusion.
Poor HO2S No. 1 and MAF sensor connections at PCM.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Start and operate engine to normal operating temperature. Operate vehicle until scan tool indicates closed-loop operation. Observe the short term FT parameter on scan tool. If scan tool displays less than 15 percent, go to next step. If scan tool does not display less than 15 percent, go to step 4 .
Turn ignition on, with engine off. Clear DTCs. Operate vehicle within FREEZE FRAME conditions. Observe the total fuel trim parameter on scan tool. If scan tool displays less than 33 percent, problem is intermittent. If scan tool does not display less than 33 percent, go to next step.
Turn ignition off. Visually and physically check for splits, kinks, and improper connections in vacuum hoses. Check PCV for proper operation. Check for any exhaust system leaks near the HO2S. Check for correct operation of EVAP control system. Repair as necessary. After repairs, go to step 11 . If no problem is found, go to next step.
Start and operate engine to normal operating temperatures. Observe operation of MAP, ECT and TP sensors. Compare the observed sensor readings with the typical scan tool data values. See appropriate PIDS VALUE CHARTS article. Check cause of any errant sensor readings. Repair as necessary. After repairs, go to step 11 . If no problem is found, go to next step.
Turn ignition off. Install Fuel Pressure Gage (J-34730-1A). Start engine. Observe fuel pressure with engine idling at normal operating temperatures. If fuel pressure is 39-50 psi (270-310 kPa), go to next step. If fuel pressure is not 39-50 psi (270-310 kPa), diagnose fuel system.
Check fuel for excessive water, alcohol, or other contaminants. If fuel is contaminated, go to next step. If no problem is found, go to step 9 .
Replace any contaminated fuel. After replacing fuel, go to step 11 .
Check fuel injectors for normal and even discharge. Fuel should be dispersed in a conical spray pattern. Check injector resistance. See appropriate SYSTEM & COMPONENT TESTING article. If no problem is found, check for intermittent connections in injector circuit. If a problem is found, go to next step.
Replace any faulty fuel injectors. After repairs, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for running this DTC or until DTC P0174 diagnostic test has run. Recheck DTCs. If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Turn ignition on, with engine off. Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no DTCs are displayed, system is okay.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Start and warm engine to normal operating temperature. Operate vehicle until scan tool indicates closed-loop. Observe short term FT parameter on scan tool. If scan tool displays greater than 11 percent, go to next step. If scan tool does not display greater than 11 percent, go to step 4 .
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within the FREEZE FRAME conditions. Observe the total fuel trim parameter on scan tool. If scan tool displays less than 33 percent, check for restriction in inlet air passage, correct fuel pressure, malfunctioning MAF sensor, or damaged wiring harness. If scan tool does not display less than 33 percent, go to next step.
Turn ignition off. Visually/physically inspect air filter and air filter assembly for restrictions. Repair as necessary. After repairs, go to step 10 . If no problem is found, go to next step.
Install Fuel Pressure Gage (J-34730-1A). Start engine. Observe fuel pressure with engine idling at normal operating temperatures. If fuel pressure is 36-43 psi (250-300 kPa), go to next step. If fuel pressure is not 36-43 psi (250-300 kPa), diagnose fuel system.
Check EVAP control system for possible over purging of fuel vapors. Repair as necessary. After repairs, go to step 10 . If no problem is found, go to next step.
Remove HO2S bank 1 sensor 1. Visually inspect sensor for damage or contamination. Repair cause of contamination before replacing a contaminated HO2S. Replace sensor if any damage or contamination is evident. After replacing sensor, go to step 10 . If sensor is okay, go to next step.
Check fuel injectors for normal or even discharge. Ensure that fuel does not leak from the ball valve of injector. Ensure fuel is dispersed in a conical spray pattern. Check injector resistance. If no problem is found, check for restriction in inlet air passage, correct fuel pressure, malfunctioning MAF sensor, or damaged wiring harness. If a problem is found, go to next step.
Replace any faulty fuel injectors. After replacing injector(s), go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for running the DTC or until this DTC test has run. See «CODE ENABLE CRITERIA»(ref-99188-S26295180842001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Turn ignition on, with engine off. Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no DTCs are displayed, system is okay.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Start engine and observe for a misfire at idle. If a misfire is present, go to step 4 . If a misfire is not present, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If this DTC resets, go to next step. If this DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S10175217452001062700000) .
Turn ignition off. Visually and physically check the following items: Improperly operating or leaking PCV valve. Incorrect PCV valve. Vacuum leak at intake manifold or gasket. Vacuum leak at a cracked, split or worn vacuum hose. Repair as necessary. After repairs, go to step 18 . If no problem(s) exists, go to next step.
Disconnect fuel injector harness connectors. Remove No. 1 ignition coil. Install a spark tester to No. 1 ignition coil spark plug boot. Crank engine while observing spark tester. Repeat procedure on all ignition coils. If any ignition coil indicates a weak spark, go to next step. If spark is okay on all ignition coils, go to step 9 .
Check ignition coils and spark plug wires for cracks, terminal corrosion, carbon tracking and moisture. Repair as necessary. After repairs, go to step 18 . If ignition coils and spark plug wires are okay, go to next step.
Turn ignition off. Swap ignition coils. Replace the suspected faulty ignition coil with a functioning ignition coil. Install Spark Tester (J-26792) and test for spark, as performed in step 4 . If test indicates a crisp Blue spark while cranking engine, go to next step. If test does not indicate a crisp Blue spark while cranking engine, diagnose Electronic Ignition (EI) system. See NO START DIAGNOSIS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
Replace the faulty ignition coil. After replacing ignition coil, go to step 18 . If no problem is found, go to next step.
Remove spark plugs. Visually and physically inspect each spark plugs for correct performance and condition. Replace as necessary. After replacing spark plugs, go to step 12 . If spark plugs were okay, go to next step.
Turn ignition off. Disconnect fuel injector harness connectors. Install Injector Test Light (J-34730-2B) into each of the fuel injector harness connectors one at time. Observe injector test light for each injector while cranking engine. If injector test light flashes for each fuel injector while cranking engine, go to next step. If injector test light does not flash for each fuel injector while cranking engine, diagnose fuel injector circuit. See FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article.
Check fuel injectors for proper operation. See FUEL INJECTOR BALANCE TEST under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. If a faulty fuel injector is found and replaced, go to step 18 . If no problem is found, go to step 14 .
If a spark plug was replaced due to rich fueling condition or wet fuel fouling, see BASIC FUEL SYSTEM CHECKS (GASOLINE) in appropriate BASIC DIAGNOSTIC PROCEDURES article. If sparks plugs were okay, go to next step.
If a spark plug is replaced because of fuel, oil or coolant fouling, go to step 15 . If a spark plug is not replaced because of fuel, oil or coolant fouling, go to step 18 .
Check EGR valve for excessive flow or sticking open. Repair as necessary. After repairs, go to step 18 . If EGR valve is okay, go to next step.
Check engine for the following mechanical problems: Worn or faulty camshaft. Leaky or sticky valves. Excessive valve deposits. Broken or leaky piston rings. Weak valve springs. Incorrect valve timing. Intake (vacuum) leaks. Leaking head gasket. Loose or broken motor mounts. Repair as necessary. After repairs, go to step 18 . If no problem exists, go to next step.
Remove CMP sensor (sensor is located on rear of cylinder head). Check CMP sensor for damage, foreign material on sensor (magnet) surface, and water or corrosion at connector terminals. Repair as necessary. After repairs, go to step 18 . If CMP sensor is okay, go to next step.
Check CMP sensor signal rotor in CMP sensor housing for damaged teeth, foreign material, and correct installation. Repair as necessary. After repairs, go to step 18 . If CMP sensor signal rotor is okay, see «DIAGNOSTIC AIDS»(ref-99188-S10175217452001062700000) .
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for running the DTC or until this DTC test has run. See «CODE ENABLE CRITERIA»(ref-99188-S12641739162001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Turn ignition on, with engine off. Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no DTCs are displayed, system is okay.

If DTCs other than P0300-P0304 are set, diagnose those DTCs first. Check the following and repair as necessary

Engine overheating.
Vacuum leaks.
EGR system for proper operation.
PCV system for proper operation.
Malfunctioning fuel injectors. Fuel injector resistance should be 13-16 ohms at 68°F (20°C).
Fuel pressure.
Ignition system for proper operation.
Engine mechanical malfunction.
Damaged wiring harness.
Defective crankshaft timing belt pulley.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Start engine. If a misfire is present at idle, go to step 4 . If misfire is not present, go next step.
Turn ignition on, with engine off. Using scan tool, clear scan tool information. Operate vehicle within FREEZE FRAME data. If DTC P0301-P0304 resets, go to next step. If DTC P0301-P0304 does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S23846987032001062700000) .
Turn ignition off. Perform a visual and a physical inspection for incorrectly operating or leaking PCV valve, incorrect PCV valve, vacuum leak at intake manifold or gasket, vacuum leak at a cracked, split, or worn vacuum hose. Repair as necessary. After repairs, go to step 15 . If no problem is found, go to next step.
Remove ignition coil of suspect cylinder. Connect harness connector to ignition coil. Install Spark Tester (J-26792) at the end of spark plug boot of ignition coil. Crank engine while observing spark tester. If a crisp Blue spark is present while cranking engine, go to step 8 . If a weak spark is present, go to next step.
Visually and physically inspect ignition coil boot for carbon tracking, insulation damage or corroded terminals. Replace ignition coil boot as necessary. After repairs, go to step 15 . If no problem is found, go to next step.
Perform a visual and a physical inspection of ignition coil for cracks, moisture, faulty connections, carbon tracking or corrosion. Replace ignition coil and boot as necessary. After repairs, go to step 15 . If no problem is found, diagnose ignition system.
Remove spark plug from misfiring cylinder. Visually and physically inspect spark plug for a faulty condition. Replace as necessary. After replacing spark plug, go to step 11 . If spark plug is okay, go to next step.
Disconnect fuel injector of each misfiring cylinder. Install Injector Test Light (J-34730-2B) into fuel injector harness connector of misfiring cylinder. Observing test light while cranking engine. Repeat test for each misfiring cylinder. If fuel injector test light flash for every test while cranking engine, go to next step. If test light did not flash on every test, diagnose fuel injector circuit. See FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article.
Test all suspect fuel injectors for proper operation. Replace any faulty fuel injectors, then go to step 15 . If injectors are okay, go to step 12 .
If spark plug was replaced due to fuel, oil or coolant fouling, go to next step. If spark plug was replaced due to other reasons, go to step 15 .
Check for engine mechanical concerns that could affect misfiring cylinder such as worn or faulty camshaft, leaking or sticking valves, excessive valve deposits, broken or leaking piston rings, weak valve springs, incorrect valve timing, intake leaks, leaking head gasket, or loose or broken motor mount. Repair as necessary. After repairs, go to step 15 . If no problem is found, go to next step.
Remove Camshaft Position (CMP) sensor (located behind cylinder head). Visually inspect CMP sensor for physical damage, foreign material on sensor (magnet) surface, water or corrosion at harness terminals. Repair as necessary. After repairs, go to step 15 . If no problem is found, go to next step.
Visually inspect CMP sensor signal rotor in camshaft sensor housing for damaged teeth, foreign material or incorrect installation. Repair as necessary. After repairs, go to next step. If no problem is found, see «DIAGNOSTIC AIDS»(ref-99188-S23846987032001062700000) .
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the conditions for running the DTCs. See «CODE ENABLE CRITERIA»(ref-99188-S01472157622001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are displayed, system is okay.

If DTCs other than P0300-P0304 are set, diagnose those DTCs first. Check the following and repair as necessary

Engine overheating.
Vacuum leaks.
EGR system for proper operation.
PCV system for proper operation.
Malfunctioning fuel injectors. Fuel injector resistance should be 13-16 ohms at 68°F (20°C).
Fuel pressure.
Ignition system for proper operation.
Engine mechanical malfunction.
Damaged wiring harness.
Defective crankshaft timing belt pulley.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Start engine. If misfire is present at idle, go to step 4 . If a misfire is not present, go to next step.
Turn ignition on, with engine off. Clear scan tool information. Operate vehicle within FREEZE FRAME data. If DTC P0301-P0306 is set, go to next step. If DTC P0301-P0306 is not set, see «DIAGNOSTIC AIDS»(ref-99188-S24161068242001070200000) .
Turn ignition off. Perform visual and a physical inspection for incorrectly operating or leaking PCV valve. Check for incorrect PCV valve, vacuum leak at intake manifold or gasket, vacuum leak at a cracked, split or worn vacuum hose. Repair as necessary. After repairs, go to step 15 . If no problem is found, go to next step.
Remove ignition coil of suspect cylinder. Connect harness connector to ignition coil. Install Spark Tester (J-26792) at the end of spark plug boot of ignition coil. Crank engine while observing spark tester. If spark tester indicates a crisp Blue spark while cranking engine, go to step 8 . If a weak spark is noted, go to next step.
Inspect ignition coil boot for carbon tracking, insulation damage, corroded terminals. Replace ignition coil boot as necessary. After repairs, go to step 15 . If no problem is found, go to next step.
Perform a visual and a physical inspection of ignition coil for cracks, moisture, faulty connections, carbon tracking or corrosion. Replace ignition coil and boot as necessary. After repairs, go to step 15 . If no problem is found, diagnose electronic ignition system.
Remove spark plug from misfiring cylinder. Visually and physically inspect spark plug for faulty condition. Replace as necessary. After replacing spark plug, go to step 11 . If spark plug is okay, go to next step.
Disconnect fuel injector of each misfiring cylinder. Install Injector Test Light (J-34730-2B) to fuel injector harness connector of a misfiring cylinder. Test fuel injector circuit by observing test light while cranking engine. Repeat action in step 3 and the test in step 4 for each misfiring cylinder. If fuel injector test light flashes for every test while cranking the engine, go to next step. If fuel injector test light does not flash for every test while cranking the engine, diagnose fuel injector circuit.
Test all suspect fuel injectors for proper operation. See appropriate SYSTEM & COMPONENT TESTING article. If any faulty fuel injector(s) were found and replaced, go to step 15 . If injector(s) are okay, go to step 12 .
If a spark plug was replaced because of fuel, oil or coolant fouling, go to next step. If a spark plug was replaced due to other fault, go to step 15 .
Check for engine mechanical concerns that could affect a misfiring cylinder. Check for worn or faulty camshaft, leaking or sticking valves, excessive valve deposits, broken or leaking piston rings, weak valve springs, incorrect valve timing, intake (vacuum) leaks, leaking head gasket, or loose or broken motor mount. Repair as necessary. After repairs, go to step 15 . If no problem is found, go to next step.
Remove CMP sensor. Inspect CMP sensor for physical damage, foreign material on sensor (magnet) surface, or water/corrosion at harness terminals. Repair as necessary. After repairs, go to step 15 . If no problem is found, go to next step.
Visually inspect CMP sensor signal rotor in camshaft sensor housing for damaged teeth or foreign material. Repair as necessary. After repairs, go to next step. If no problem is found, see «DIAGNOSTIC AIDS»(ref-99188-S24161068242001070200000) .
Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the conditions for running the DTCs. If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are displayed, system is okay.

If DTCs other than P0300-P0306 are set, diagnose those DTCs first. Check the following and repair as necessary

Engine overheating.
Vacuum leaks.
EGR system for proper operation.
PCV system for proper operation.
Malfunctioning fuel injectors.
Fuel pressure.
Ignition system for proper operation.
Engine mechanical malfunction.
Damaged wiring harness.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Recheck DTCs. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S10256011702001062900000).
Turn ignition off. Disconnect KS harness connector. Using a DVOM connected to ground, probe KS harness connector terminal. Turn ignition on, with engine off. If voltage reading is 4-5 volts, go to next step. If voltage reading is not 4-5 volts, go to step 6.
Turn ignition off. Reconnect KS harness connector. Using DVOM connected to ground, backprobe KS signal circuit at PCM harness connector terminal No. C2 terminal No. 3 (Black wire). see scheme 3or see scheme 4. Start engine. Monitor output of KS signal with engine running. If voltage reading is 0.90-3.98 volts, see «DIAGNOSTIC AIDS»(ref-99188-S10256011702001062900000). If voltage reading is not 0.90-3.98 volts, go to next step.
Turn ignition off. Replace knock sensor. After replacing sensor, go to step 8.
Turn ignition off. Check for short in Black wire between KS and PCM. Ensure terminal connection at sensor is good. Repair as necessary. Repair as necessary. After repairs, go to step 8. If circuit is okay, go to next step.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Remove DOME fuse for 30 seconds (fuse is located on passenger compartment fuse/relay block). Reinstall fuse. Reset radio clock time. Start and operate vehicle within the conditions for running the DTC or until DTC P0327 diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S16777511212001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no other DTCs are displayed, system is okay.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, clear DTC. Operate vehicle within FREEZE FRAME conditions. Recheck DTCs. If DTC resets, go to next step. If DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S27009611532001062900000) .
Turn ignition off. Disconnect KS harness connector. Using a DVOM connected to ground, probe KS sensor harness connector terminal (Black wire). Turn ignition on, with engine off. If voltage reading is 4-5 volts, go to next step. If voltage reading is not 4-5 volts, go to step 6 .
Turn ignition off. Reconnect KS harness connector. Using DVOM connected to ground, backprobe PCM harness connector C2 terminal No. 3 (Black wire). Start engine. Monitor output of KS signal with engine running. If voltage reading is 0.90-3.98 volts, see «DIAGNOSTIC AIDS»(ref-99188-S10256011702001062900000) . If voltage reading is not 0.90-3.98 volts, go to next step.
Turn ignition off. Replace knock sensor. After replacing sensor, go to step 8 .
Turn ignition off. Check for open in Black wire between KS and PCM. Ensure terminal connection at sensor is good. Repair as necessary. After repairs, go to step 8 . If circuit is okay, go to next step.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within the conditions for running the DTC. See «CODE ENABLE CRITERIA»(ref-99188-S16777511212001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are displayed, system is okay.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If this DTC resets, go to next step. If this DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S32902405162001062700000).
Turn ignition off. Disconnect CKP sensor harness connector (sensor is located near crankshaft pulley). Using DVOM, check resistance between CKP sensor harness connector terminals No. 2 (Orange/Blue wire) and No. 3 (White/Blue wire). see scheme 8 If resistance is 484-656 ohms at 68°F (20°C), go to next step. If resistance is not 484-656 ohms at 68°F (20°C), go to step 6.
Turn ignition off. Disconnect PCM harness connector C4 on 2.0L or C2 on 2.5L. Check for open or short in Orange/Blue or White/Blues wires between CKP sensor and PCM. Repair as necessary. After repairs, go to step 8. If circuits are okay, go to next step.
Check for poor connections at PCM and CKP sensor. Repair as necessary. After repairs, go to step 8. If connections are okay, go to next step 7.
Turn ignition off. Replace CKP sensor. After replacing sensor, go to step 8.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition off. On 2.0L, clear DTCs by removing DOME fuse for 30 seconds. Reinstall fuse and reset radio clock time. On 2.5L, turn ignition on with engine off and clear DTCs using scan tool. Turn ignition off for 30 seconds. On all models, start engine and operate vehicle within the conditions for running the DTC or until DTC P0335 diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S02802620482001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no other DTCs are displayed, system is okay.

CKP sensor performance may be affected by temperature. Check CKP sensor operation and internal resistance at various temperatures. Check for water intrusion in CKP sensor wiring harness boots. Check CKP sensor signal rotor for foreign material or damaged teeth. If DTC sets while driving but checks out okay, check for an inadequate CKP sensor circuit shielding. Ensure CKP sensor circuit is properly shielded and drain wire is properly grounded.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If this DTC resets, go to next step. If this DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S21954780602001062700000).
Turn ignition off. Disconnect CMP sensor harness connector. Turn ignition on, with engine off. Using DVOM, check voltage between ground and CMP sensor harness connector terminal No. 1 (Blue/Black wire) on 2.0L or terminal No. 2 (Blue/Black wire) on 2.5L. see scheme 2 If battery voltage is present, go to next step. If battery voltage is not present, go to step 7.
Using a test light connected to battery voltage, probe CMP sensor harness connector terminal No. 3 (Purple/Red wire) on 2.0L or terminal No. 1 (Gray/Yellow wire) on 2.5L. If test light illuminates, go to next step. If test light does not illuminate, go to step 8.
Using DVOM, check voltage at CMP sensor harness connector terminal No. 2 (Yellow/Blue wire) on 2.0L or terminal No. 4 (Yellow/Blue wire) on 2.5L. If voltage reading is 5 volts, go to next step. If voltage reading is not 5 volts, go to step 9.
Turn ignition off. Check for poor connections at PCM and CMP sensor. Check if DTC P1500 is set. Repair as necessary. After repairs, go to step 13. If connections are okay and DTC P1500 is not set, go to step 10.
Turn ignition off. Repair open in Blue/Black wire between main relay and CMP sensor. After repairs, go to step 13.
Turn ignition off. Check for open in Purple/Red wire on 2.0L or Gray/Yellow wire on 2.5L between ground and CMP sensor. Check for faulty ground connection. Repair as necessary. After repairs, go to step 13. If circuit and connection are okay, go to step 12.
Turn ignition off. Check for open in Yellow/Blue wire on 2.0L or Yellow/Blue or Yellow/Green wires on 2.5L between CMP sensor and PCM. Repair as necessary. After repairs, go to step 13. If circuit is okay, go to step 12.
Remove CMP sensor and housing. Check for CMP sensor signal rotor not rotating, signal rotor missing teeth or damaged teeth, and foreign material on CMP sensor. Repair as necessary. After repairs, go to step 13. If CMP sensor is okay, go to next step.
Replace CKP sensor. After replacing sensor, go to step 13.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
On 2.0L, clear DTCs by removing DOME fuse for 30 seconds. Reinstall fuse and reset radio clock time. On 2.5L, turn ignition on with engine off and clear DTCs using scan tool. Turn ignition off for 30 seconds. On all models, start engine and operate vehicle within the conditions for running the DTC or until this DTC diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S33443650482001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no other DTCs are displayed, system is okay.

If CMP sensor circuitry is okay, check CMP sensor signal rotor for proper alignment or damage.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, check for DTCs. If DTC P0403 is also set, go to «DTC P0403»(ref-99188-S42095692192001062700000). If DTC P0403 is not set, go to next step.
Start and warm engine to normal operating temperatures. If engine runs rough or if idle is unstable, go to step 12. If engine does not run rough or if idle is not unstable, go to next step.
Using scan tool, clear DTCs. Start engine. Using scan tool, gradually command EGR valve to open 100 percent. If engine runs rough or stalls, go to step 10. If engine does not run rough or does not stall, go to next step.
Using a test light connected to ground, backprobe EGR valve harness connector terminals No. 1 (Light Green wire) and No. 4 (Light Green/Red wire). see scheme 9 If test light illuminates on both circuits, continue to backprobe both EGR control circuits while commanding EGR valve to open at 5 percent using scan tool. Test light should illuminate and then turn off when EGR valve is commanded open. If test light operates as commanded, go to next step. If test light does not operate as commanded, go to step 7.
Using test light connected to ground, backprobe EGR valve harness connector terminals No. 3 (Light Green/White) and No. 6 (Light Green/Yellow wire). Test light should not illuminate on both circuits. Continue to backprobe both EGR control circuits while commanding the EGR valve open at 5 percent using scan tool. Test light should illuminate when EGR valve is commanded open. If test light operates as commanded, go to step 8. If test light does not operate as commanded, go to next step.
Turn ignition off. Disconnect EGR valve harness connector. Using a DVOM, check resistance between EGR valve terminals No. 1 and 2; terminals No. 2 and 3; terminals No. 5 and 6; terminals No. 4 and 5. see scheme 9 Resistance should be 20-24 ohms at 68°F (20°C). Check resistance between EGR valve body and EGR valve terminals No. 2 and 5. Resistance should be infinite. If resistance readings are as specified, go to step 9. If resistance readings are not as specified, go to step 17.
Turn ignition off. Remove EGR valve. Check all EGR passages for any obstruction or blockage. Check EGR valve for physical damage or carbon deposits. Repair or replace as necessary. After repairs, go to step 19. If no problem is found, go to step 17.
Disconnect EGR valve harness connector. Turn ignition on, with engine off. Connect a test light between ground and EGR valve harness connector terminal No. 2 (Blue/Black wire), then to terminal No. 5 (Blue/Black wire). see scheme 9 If test light illuminated on both circuits, go to step 16. If test light did not illuminate on both circuits, go to step 15.
Turn ignition off. Check vehicle for any condition that can affect accuracy of MAP sensor, such as a malfunctioning or incorrectly calibrated MAP sensor, faulty manifold vacuum supply to sensor or an engine performance concern that can affect engine manifold vacuum readings. Repair as necessary. After repairs, go to step 19. If no problem is found, go to next step.
Fault is not present. Check for any stored and undiagnosed DTCs and diagnose as necessary. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no DTCs are displayed, see «DIAGNOSTIC AIDS»(ref-99188-S01174271932001062700000).
With engine running, disconnect EGR valve harness connector. If engine performance improves when connector is disconnected, go to step 14. If engine performance does not improve when connector is disconnected, go to next step.
Turn ignition off. Remove EGR valve. Check EGR valve for sticking open or leaking EGR valve and gasket Repair or replace as necessary. After repairs, go to step 19.
Turn ignition off. Check for short to ground in EGR coil control circuits to PCM. Repair as necessary. After repairs, go to step 19. If circuits are okay, go to step 18.
Turn ignition off. Repair ignition positive voltage supply to EGR valve. After repairs, go to step 19.
Turn ignition off. Check for open or short in EGR coil control circuits between EGR valve and PCM. Repair as necessary. After repairs, go to step 19. If circuits are okay, go to step 18.
Replace EGR valve. After replacing EGR valve, go to step 19.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition off. Clear DTCs by removing DOME fuse for 30 seconds. Reinstall fuse and reset radio clock time. Start engine and operate vehicle within the conditions for running the DTC or until this DTC diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S23724356352001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no other DTCs are displayed, system is okay.

Normal engine operating temperature is specified as 176°F (80°C) or greater. This DTC is most likely to set during a combination of highway and city driving. Operate vehicle in stop and go situations with short trips on the highway to validate this DTC. Check the following and repair as necessary

EGR valve stuck closed, stuck open or binding.
Incorrect PCM for vehicle.
Check for a poor electrical connection at PCM.

DTC may set when expected change in MAP is greater than or less than expected value, during operation of EGR by-pass valve. Check for the following conditions that may affect accuracy of MAP sensor readings

Retarded ignition timing.
Restricted exhaust system.
Faulty MAP sensor.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Start and warm engine to normal operating temperature. If engine runs rough or idle is unstable, go to step 11. If engine idle is okay, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Start engine. Using scan tool, gradually command EGR valve open to 100 percent. If engine runs rough or stalls, go to step 9. If engine does not ran rough or does not stall, go to next step.
Using a test light connected to ground, backprobe EGR valve harness connector terminals No. 1 (Light Green wire) and No. 4 (Light Green/Yellow wire). see scheme 9 Test light should illuminate on both circuits. Continue to backprobe both EGR control circuits with test light. Observe test light on each circuit while commanding EGR valve open to 5 percent value with scan tool. Test light should illuminate and then turn off when EGR valve is commanded open. If test light activates as specified, go to next step. If test light does not activate as specified, go to step 6.
Using test light connected to ground, backprobe EGR valve harness connector terminals No. 3 (Light Green wire) and No. 6 (Light Green/Red wire). Test light should not illuminate on either circuit. Continue to backprobe both EGR control circuits with test light. Observe test light on each circuit while commanding EGR valve open to 5 percent with scan tool. Test light should illuminate when EGR valve is commanded open. If test light illuminates as specified, go to step 7. If test light does not illuminate as specified, go to next step.
Turn ignition off. Disconnect EGR valve harness connector. Using a DVOM, check EGR valve coil windings resistance between pins No. 1 and 2; pins No. 2 and 3; pins No. 5 and 6; pins No. 4 and 5. Resistance should be 20-24 ohms. Check resistance between pin No. 2 and EGR valve assembly, and between pin No. 5 and EGR assembly. Resistance should be infinite. If resistance is as specified, go to step 8. If resistance is not as specified, go to step 16.
Turn ignition off. Remove EGR valve. Check EGR passages for any obstruction or blockage. Check EGR valve for physical damage or carbon deposits. Repair as necessary. After repairs, go to step 18. If no problem is found, go to step 16.
Disconnect EGR valve harness connector. Turn ignition on, with engine off. Connect a test light between ground and EGR harness connector terminal No. 2 (Blue/Black wire), then to terminal No. 5 (Blue/Black wire). see scheme 9 If test light illuminates on both circuits, go to step 15. If test light does not illuminate on both circuits, go to step 14.
Turn ignition off. Check vehicle for any condition that can affect accuracy of MAP sensor. Check for malfunctioning or incorrectly calibrated MAP sensor, or faulty manifold vacuum supply to MAP sensor. Check engine performance concern that can affect engine manifold vacuum readings. Repair as necessary. After repairs, go to step 18. If no problem is found, go to next step.
Fault is not present. If any undiagnosed DTCs are stored, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no other DTCs are stored, see «DIAGNOSTIC AIDS»(ref-99188-S24416558372001070200000).
With engine running, disconnect EGR valve harness connector. If engine performance improves when EGR valve is disconnected, go to step 13. If engine performance does not improve, go to next step.
Remove EGR valve. Check EGR valve for sticking in open position and gasket for leaks. Repair or replace as necessary. After repairs, go to step 18.
Check EGR coil control circuits for open short to ground. Repair as necessary. After repairs, go to step 18. If circuits are okay, go to step 17.
Turn ignition off. Repair Blue/Black wire between main relay and EGR valve. After repairs, go to step 18.
Turn ignition off. Check for open or short in EGR coil control circuits that did not turn test light on and off in steps 4 or 5. Repair as necessary. After repairs, go to step 18. If circuit are okay, go to step 17.
Replace EGR valve. After replacing EGR valve, go to step 18.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for running the DTC or until this DTC diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S15190586672001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no other DTCs are displayed, system is okay.

EGR valve stuck closed, stuck open or binding.
Incorrect PCM for vehicle.
Check for a poor electrical connection at PCM.

Retarded ignition timing.
Restricted exhaust system.
Faulty MAP sensor.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Turn ignition off. Disconnect EGR valve harness connector. Turn ignition on, with engine off. Connect a test light between ground and EGR valve harness connector terminal No. 2 (Blue/Black wire). see scheme 9 Connect test light between ground and EGR valve harness connector terminal No. 5 (Blue/Black wire). If test light illuminates at both terminals, go to next step. If test light does not illuminate at both terminals, go to step 7.
Turn ignition off. Using DVOM, check resistance between the following terminals at EGR valve assembly. Terminals No. 1 (Light Green wire) and No. 2 (Blue/Black wire). Terminals No. 3 (Light Green/White wire) and No. 2 (Blue/Black wire). Terminals No. 4 (Light Green/Red wire) and No. 5 (Blue/Black wire). Terminals No. 6 (Light Green/Yellow wire) and No. 5 (Blue/Black wire). Resistance should be 20-24 ohms at 68°F (20°C). Check resistance between EGR valve body and harness connector terminal No. 2 (Blue/Black wire) and No. 5 (Blue/Black wire). Resistance should be infinite. If resistance is as specified at all terminals, go to next step. If resistance is not as specified at any of the terminals, go to step 9.
Reconnect EGR valve harness connector. Start engine. Warm engine to normal operating temperature. Using scan tool, clear DTCs. Using scan tool, gradually command EGR valve open to 100 percent. If engine runs rough or stalls, go to «DIAGNOSTIC AIDS»(ref-99188-S28862261332001062700000). If engine does not run rough or stall, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Start and operate engine for one minute or until the MIL illuminates. Recheck for DTCs. If this DTC resets, go to step 8. If this DTC does not reset, go to step 11.
Check for open or short in circuits between EGR valve and PCM. Repair as necessary. After repairs, go to step 11. If circuits are okay, go to step 10.
Turn ignition off. Repair open in Blue/Black wires between main relay and EGR valve. After repairs, go to step 11.
Check for open or short in circuits between EGR valve and PCM. Repair as necessary. After repairs, go to step 11. If circuits are okay, go to step 10.
Replace EGR valve. After replacing EGR valve, go to step 11.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition off. Remove DOME fuse for 30 seconds. Reinstall fuse. Reset radio clock time. Start engine and operate vehicle within the conditions for running the DTC or until DTC P0403 diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S41919754902001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no other DTCs are displayed, system is okay.

Normal engine operating temperature is specified as 176°F (80°C) or greater. Check the following and repair as necessary

Incorrect PCM for vehicle.
Check for a poor electrical connection at PCM.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Check if any HO2S related DTCs are set. If DTC P0131, P0132, P0133, P0134, P0135, P0136 or P0141 is set, diagnose affected DTCs first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If DTC P0131, P0132, P0133, P0134, P0135, P0136 or P0141 is not set, go to next step.
Warm engine to normal operating temperature. Ensure engine is operating in closed-loop. Operate engine at 2500-3000 RPM for 3 minutes. Using scan tool, monitor HO2S No. 1 and No. 2 signal voltage. If HO2S No. 2 signal is as active as HO2S No. 1 signal, go to step 5 . If HO2S No. 2 signal is not as active as HO2S No. 1 signal, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If this DTC resets, go to next step. If this DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S06987765642001062700000) .
Turn ignition off. Check TWC for physical damage (discoloration, holes, dents, internal rattles, etc.). If damage exists, go to step 8 . If no damage exists, go to next step.
Check exhaust system for leaks, damage, and loose or missing hardware. Repair as necessary. After repairs, go to step 9 . If exhaust system is okay, go to next step.
Check HO2S No. 2 for pigtail and wiring harness contacting exhaust pipe, looseness or road damage. Repair as necessary. After repairs, go to step 9 . If HO2S No. 2 is okay, go to next step.
Replace TWC. After repairs, go to step 10 .
Start engine. Warm engine to normal operating temperature. Ensure engine is operating in closed-loop. Operate engine at 2500-3000 RPM for 3 minutes. Using scan tool, monitor HO2S No. 1 and No. 2 signal voltage. If HO2S No. 2 signal is as active as HO2S No. 1 signal, go to «DIAGNOSTIC AIDS»(ref-99188-S06987765642001062700000) . If HO2S No. 2 signal is not as active as HO2S No. 1 signal, go to next step.
Turn ignition off. Remove DOME fuse for 30 seconds. Reinstall fuse. Reset radio clock time. Start engine and operate vehicle within the conditions for running the DTC or until DTC P0420 diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S07758786822001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are displayed, system is okay.

Check the following and repair as necessary

Exhaust gas leaks.
HO2S No. 1 and No. 2 malfunctions.
Damaged wiring harness.

TWC failure may be caused by the following conditions

Engine misfire.
Retarded ignition timing.
Inadequate secondary ignition voltage.
Excessive engine oil or engine coolant consumption.
Rich engine fueling.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Check for any HO2S related DTCs and diagnose affected DTCs first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . After repairs or if no HO2S DTCs are set, go to next step.
Start and warm engine to normal operating temperature. Ensure engine is operating in closed-loop. Operate engine at 2500-3000 RPM for 3 minutes. Using scan tool, monitor fuel control HO2S and catalyst monitor HO2S signals of suspect converter. If scan tool indicates that signals are active, go to step 5 . If scan tool does not indicate that signals are active, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If this DTC resets, go to next step. If this DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S00338842062001070200000) .
Turn ignition off. Visually and physically inspect the 3-way catalytic converter for any dents, severe discoloration caused by excessive temperatures, holes or internal rattle caused by damaged catalyst. Replace as necessary. After replacing catalytic converter, go to step 8 . If catalytic converter is okay, go to next step.
Visually and physically inspect exhaust system for any leaks, damage or loose or missing hardware. Repair as necessary. After repairs, go to step 9 . If no problem is found, go to next step.
Visually and physically inspect catalyst monitor HO2S of suspect converter for pigtail and wiring harness making contact with exhaust pipe, loose HO2S, or any road damage. Repair as necessary. After repairs, go to step 9 . If no problem is found, go to next step.
Replace TWC. After replacing converter, go to step 10 .
Start and warm engine to normal operating temperature. Ensure engine is operating in closed-loop. Operate engine at 2500-3000 RPM for 3 minutes. Monitor fuel control HO2S and catalyst monitor HO2S signals of suspect converter on scan tool. If scan tool indicates that signals are active, see «DIAGNOSTIC AIDS»(ref-99188-S00338842062001070200000) . If scan tool does not indicate that signals are active, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within conditions for running DTC. See «CODE ENABLE CRITERIA»(ref-99188-S18392962122001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Turn ignition on, with engine off. Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are displayed, system is okay.

Check the following and repair as necessary

Exhaust gas leaks.
HO2S No. 1 and No. 2 malfunctions.
Damaged wiring harness.

TWC failure may be caused by the following conditions

Engine misfire.
Retarded ignition timing.
Inadequate secondary ignition voltage.
Excessive engine oil or engine coolant consumption.
Rich engine fueling.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
If other EVAP DTCs are set except DTC P0440 or P0455, see «DIAGNOSTIC AIDS»(ref-99188-S35612009672001062700000) . If no other EVAP DTCs are set, go to next step.
Using scan tool, observe Fuel Tank Pressure (FTP) sensor parameter. Remove fuel filler cap. If FTP sensor parameter is within 0.0-0.5 in. H2O (0.0-0.9 mm Hg) with fuel filler cap removed, go to next step. If FTP sensor parameter is not within 0.0-0.5 in. H2O (0.0-0.9 mm Hg) with fuel filler cap removed, go to «DTC P0450»(ref-99188-S03272130892001062700000) .
Turn ignition off. Visually inspect the entire EVAP control system for loose hose connections, damaged or deteriorated hoses, clogged hoses, missing or damaged components, or loose or incorrect fuel filler cap. Repair as necessary. After repairs, go to step 16 . If no problem is found, go to next step.
Check EVAP canister purge valve for no manifold vacuum from intake manifold vacuum port, leaking or damaged vacuum hoses, or restricted vacuum hoses or passages. Repair as necessary. After repairs, go to step 30 . If no problem is found, go to next step.
Turn ignition on, with engine off. Disconnect vacuum hoses to EVAP canister purge valve from intake manifold and from EVAP canister. Blow air into vacuum hose that was disconnected from EVAP canister. Air should not pass through the EVAP canister purge valve and exit from intake manifold hose. Using scan tool, command EVAP canister purge valve on and adjust the duty cycle to 100 percent. Blow air into the vacuum hose that was disconnected from EVAP canister. Air should pass through EVAP canister purge valve and exit from intake manifold hose. If EVAP canister purge valve passes both inspections, go to step 9 . If EVAP canister purge valve does not pass both inspections, go to next step.
Turn ignition on, with engine off. Using a test light connected to ground, probe EVAP canister purge valve harness connector terminal No. 1 (Blue/Black wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 20 .
Using test light connected to battery voltage, probe EVAP canister purge valve harness connector terminal No. 2 (Green/Black wire). Using scan tool, command EVAP canister purge valve on. Adjust duty cycle from zero to 100 percent while monitoring test light. If test light flashes and then stay illuminated as the duty cycle reaches 100 percent, go to step 28 . If test light does not flash or stay illuminated as duty cycle reaches 100 percent, go to step 27 .
Turn ignition off. Remove EVAP canister vent solenoid. Blow air into EVAP canister vent solenoid port, located on side that was connected to EVAP canister air filter. If air passes through to other side of vent valve, go to next step. If air does not pass through to other side of vent valve, go to step 25 .
Using scan tool, command EVAP canister vent solenoid on. Blow air into EVAP canister vent solenoid port, located on side that was connected to EVAP canister air filter. If air does not pass through the vent solenoid, go to next step. If air passes through the vent solenoid, go to step 12 .
Continue to blow air into EVAP canister vent solenoid. Command EVAP canister vent solenoid off with scan tool. If air passes through the EVAP canister vent solenoid when scan tool commanded vent valve off, go to step 14 . If does not pass through EVAP canister vent solenoid when scan tool commanded vent solenoid off, go to step 21 .
Turn ignition off. Disconnect EVAP canister vent solenoid harness connector. Turn ignition on, with engine off. Using a test light connected to ground, probe EVAP canister vent solenoid harness terminal No. 1 (Blue/Black wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 20 .
Using scan tool, command EVAP canister vent solenoid on. Using test light connected to battery voltage, probe EVAP canister vent solenoid harness connector terminal No. 2 (Purple/Red wire). If test light illuminates, go to step 25 . If test light does not illuminate, go to step 23 .
Turn ignition on, with engine off. Remove fuel cap and install gas cap adapter. Connect EVAP Pressure/Purge Diagnostic Station (J-41413) to gas cap adapter. Command EVAP canister vent solenoid on with scan tool. Pressurize EVAP system to 15 in. H2O (28 mm Hg) using EVAP pressure/purge diagnostic station. Monitor pressure using gauge on diagnostic station. Turn the rotary switch on EVAP pressure/purge diagnostic station to HOLD position and observe EVAP pressure gauge. If pressure decrease to less than 10 in. H2O (18.6 mm Hg) within 2 minutes, go to next step. If pressure does not decrease to less than 10 in. H2O (18.6 mm Hg) within 2 minutes, go to step 17 .
Continuously attempt to pressurize EVAP system to 30 in. H2O (56 mm Hg). Locate any leaks in the EVAP system using the Ultrasonic Leak Detector (J-41416). Partially lower fuel tank in order to examine the top tank connections. If leaks are found, go to next step. If no leaks are found, go to step 17 .
Turn ignition off. Repair or replace any leaking or faulty EVAP control system components. After repairs, go to step 30 .
Disconnect the vacuum/vapor hoses from EVAP canister. Blow air into the tank port of EVAP canister. There should be no restriction of air flow through the canister and out the purge pipe and air port. If EVAP canister passed the test, go to next step. If EVAP canister did not pass the test, go to step 22 . CAUTION: DO NOT breathe air through the EVAP component tubes or hoses. Fuel vapors inside EVAP components may cause personal injury.
Turn ignition off. Remove Fuel Tank Pressure (FTP) control valve. Connect a vacuum hose to canister side port of FTP control valve. Blow air into hose on FTP control valve. If air flows through the valve to the tank port side, go to next step. If air does not flow, go to step 26 . NOTE: FTP control valve allows vapor to flow from fuel tank to canister when fuel tank pressure is greater than canister pressure by more than 0.5 psi (3.5 kPa).
Move vacuum hose to fuel tank port of FTP control valve. Blow hard into hose connected to tank port side of FTP control valve. Air should flow easily through the valve and out of canister port. If FTP control valve passes this test, go to step 24 . If FTP control valve does not pass this test, go to step 26 .
Turn ignition off. Repair open in Blue/Black wire. After repairs, go to step 30 .
Turn ignition off. Check for short to ground in Purple/Red wire between EVAP canister vent solenoid and PCM. Repair as necessary. After repairs, go to step 30 . If circuit is okay, go to step 29 .
Replace EVAP canister. After replacing EVAP canister, go to step 30 .
Turn ignition off. Check for open in Purple/Red wire between EVAP canister vent solenoid and PCM. Repair as necessary. After repairs, go to step 30 . If circuit is okay, go to step 29 .
Check EVAP canister filter and hoses for restrictions or blockage. Repair as necessary. After repairs, go to step 30 . If no problem is found, see «DIAGNOSTIC AIDS»(ref-99188-S35612009672001062700000) .
Turn ignition off. Replace EVAP canister vent solenoid. After replacing vent solenoid, go to step 30 .
Replace FTP control valve. After replacing control valve, go to step 30 .
Turn ignition off. Check for open or short in Green/Black wire between EVAP canister purge valve and PCM. Repair as necessary. After repairs, go to step 30 . If circuit is okay, go to step 29 .
Turn ignition off. Replace EVAP canister purge valve. After replacing purge valve, go to step 30 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the FREEZE FRAME conditions that set the DTC or until DTC P0440 diagnostic test has run. If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are displayed, system is okay.

DTC is most likely to set during city driving. Avoid operating vehicle for long periods of time on the highway to validate DTC. Check the following and repair as necessary

Cracked or punctured EVAP canister.
Damaged or disconnect source vacuum line, EVAP purge line, vent hose or fuel tank vapor line.
Faulty or erratic fuel level sensor.
Faulty or erratic fuel tank pressure sensor.
Faulty EVAP canister purge valve.
Faulty EVAP canister vent solenoid.
Faulty EVAP tank pressure control solenoid vacuum valve.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
If other EVAP DTCs are set except DTC P0455, see «DIAGNOSTIC AIDS»(ref-99188-S33152283592001062900000) . If no other EVAP DTCs are set, go to next step.
Turn ignition off. Visually inspect entire EVAP control system for any loose hose connections, damaged or deteriorated hoses, clogged hoses, missing or damaged components, faulty terminal connections on any related components, or a loose or faulty fuel cap. Repair as necessary. After repairs, go to step 21 . If no problem is found, go to next step. CAUTION: DO NOT breathe the air through the EVAP component tubes or hoses. Fuel vapors inside EVAP components may cause personal injury.
Remove Fuel Tank Pressure (FTP) control valve. Blow air through the valve from canister port. If air flows through valve to tank port side, go to next step. If air does not flow through valve to tank port side, go to step 29 . NOTE: FTP control valve will not allow air to flow from tank side port to canister side port until pressure on the tank port side is greater than 0.5 psi (3.5 kPa).
Blow hard through valve from tank port side. Air should flow through valve to the canister port. Apply 15 in. Hg (51 kPa) of vacuum to vacuum port of FTP control valve using a vacuum pump. With vacuum applied, blow gently through the tank side port. Air should flow easily through to the canister port. If FTP control valve passes both checks, go to next step. If FTP control valve does not pass both checks, go to step 29 .
Turn ignition on, with engine off. Using scan tool, command EVAP tank pressure control solenoid valve on. Disconnect vacuum hoses from EVAP tank pressure control solenoid valve. Blow air through EVAP fuel tank pressure control solenoid valve side of EVAP tank pressure control solenoid valve. If air passes through the valve and out the manifold vacuum side, go to next step. If air does not pass through the valve and out the manifold vacuum side, go to step 8 .
Turn ignition off. Check vacuum hoses and intake manifold port for any restrictions or leaks. Repair as necessary. After repairs, go to step 35 . If no problem is found, go to step 10 .
Turn ignition off. Disconnect EVAP tank pressure control solenoid valve harness connector. Turn ignition on, with engine off. Using a test light connected to ground, probe harness side of EVAP tank pressure control solenoid valve connector terminal No. 1 (Blue/Black wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 23 .
Connect test light to battery voltage and probe the harness side EVAP tank pressure control solenoid valve connector terminal No. 2 (Green/White wire). Using scan tool, command EVAP tank pressure control solenoid valve off. Test light should not illuminate. Command EVAP tank pressure control solenoid valve on. If test light illuminates, go to step 33 . If test light does not illuminate, go to step 32 .
Check EVAP canister purge valve for vacuum from intake manifold vacuum port, leaks, damaged vacuum hoses or restricted vacuum hoses or passages. Repair as necessary. After repairs, go to step 35 . If no problem is found, go to next step.
Turn ignition on, with engine off. Disconnect vacuum hoses to EVAP canister purge valve from intake manifold and EVAP canister. Blow air into vacuum hose that was disconnected from EVAP canister. Air should not pass through EVAP canister purge valve and exit from intake manifold hose. Using scan tool, command EVAP canister purge valve on and adjust the duty cycle to 100 percent. Blow air into vacuum hose that was disconnected from EVAP canister. Air should pass through EVAP canister purge valve and exit from intake manifold hose. If EVAP canister purge valve passes both inspections, go to step 14 . If EVAP canister purge valve does not pass both inspections, go to next step.
Using a test light connected to ground, probe ignition positive voltage circuit at EVAP canister purge valve harness connector terminal No. 1 (Blue/Black wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 23 .
Connect test light to battery voltage and probe EVAP canister purge valve harness connector terminal No. 2 (Green/Black wire). Using scan tool, command EVAP canister purge valve on. Adjust duty cycle from 0-100 percent while monitoring test light. If test light flash and then illuminate fully as duty cycle reaches 100 percent, go to step 31 . If test light does not flash, go to step 30 .
Turn ignition off. Remove canister hose from EVAP canister vent solenoid. Using a vacuum pump, apply 15 in. Hg (51 kPa) to canister side of EVAP canister vent solenoid. If valve holds vacuum, go to step 27 . If valve does not hold vacuum, go to next step.
Turn ignition on, with engine off. Using scan tool, command EVAP canister vent solenoid on. Apply 15 in. Hg (51 kPa) of vacuum to canister side of EVAP canister vent solenoid. If EVAP canister vent solenoid holds the vacuum, go to next step. If EVAP canister vent solenoid does not hold the vacuum, go to step 17 .
While EVAP canister vent solenoid is still holding vacuum, use scan tool to command EVAP canister vent solenoid off. If vacuum decreases to zero, go to step 19 . If vacuum does not decrease to zero, go to step 24 .
Turn ignition off. Disconnect EVAP canister vent solenoid harness connector. Turn ignition on, with engine off. Using test light connected to ground, probe EVAP canister vent solenoid harness connector terminal No. 1 (Blue/Black wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 23 .
Using scan tool, command EVAP canister vent solenoid on. Using test light connected to battery voltage, probe EVAP canister vent solenoid harness connector terminal No. 2 (Purple/Red wire). If test light illuminates, go to step 28 . If test light does not illuminate, go to step 26 .
Remove fuel cap and install gas cap adapter. Connect EVAP Pressure/Purge Diagnostic Station (J-41413) to gas cap adapter. Apply vacuum to pressure control valve vacuum port. Using scan tool, command EVAP canister vent solenoid on. Using diagnostic station, pressurize EVAP system to 15 in. H2O (28 mm Hg). Monitor pressure using gauge on diagnostic station. Turn rotary switch on diagnostic station to HOLD position and observe EVAP pressure gauge. If pressure decreases to less than 10 in. H2O (18.6 mm Hg) within 2 minutes, go to next step. If pressure does not decrease to less than 10 in. H2O (18.6 mm Hg), go to step 22 .
Continuously attempt to pressurize EVAP system to locate any leaks in EVAP system using the Ultrasonic Leak Detector (J-41416). Partially lower fuel tank in order to examine top tank connections. If leaks are found, go to next step. If no leaks are found, go to step 22 .
Turn ignition off. Replace any leaking or faulty EVAP control system components. After repairs, go to step 35 .
Disconnect vacuum hoses from EVAP canister and block vent valve port. Connect vacuum pump to tank port and attempt to obtain 10 in. H2O (18.6 mm Hg) of vacuum pressure. Pressure should bleed through the canister and out the purge port with no restrictions. If vacuum gauge indicates any pressure, go to step 25 . If vacuum gauge does not indicate any pressure, see «DIAGNOSTIC AIDS»(ref-99188-S33152283592001062900000) .
Turn ignition off. Repair open in Blue/Black wire to main relay. After repairs, go to step 35 .
Turn ignition off. Check for short to ground in Purple/Red wire between EVAP canister vent solenoid and PCM. Repair as necessary. After repairs, go to step 35 . If circuit is okay, go to step 34 .
Turn ignition off. Replace EVAP canister. After replacing canister, go to step 35 .
Turn ignition off. Check for open in Purple/Red wire. Repair as necessary. After repairs, go to step 35 . If circuit is okay, go to step 34 .
Check vacuum hoses of EVAP canister vent solenoid for restrictions. Repair as necessary. After repairs, go to step 35 . If vacuum hoses are okay, go to next step.
Turn ignition off. Replace EVAP canister vent solenoid. After replacing vent solenoid, go to step 35 .
Replace FTP control valve. After replacing control valve, go to step 35 .
Turn ignition off. Check for open or short in Green/Black wire. Repair as necessary. After repairs, go to step 35 . If circuit is okay, go to step 34 .
Turn ignition off. Replace EVAP canister purge valve. After replacing purge valve, go to step 35 .
Turn ignition off. Check for open or short in Green/Black wire. Repair as necessary. After repairs, go to step 35 . If circuit is okay, go to step 34 .
Turn ignition off. Replace EVAP tank pressure control solenoid valve. After replacing EVAP tank pressure control solenoid valve, go to step 35 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine an operate vehicle within the conditions for running the DTC or until DTC P0440 diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S22358808982001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are displayed, system is okay.

DTC is most likely to set during city driving. Avoid operating vehicle for long periods of time on the highway to validate DTC. Check the following and repair as necessary

Cracked or punctured EVAP canister.
Damaged or disconnect source vacuum line, EVAP purge line, vent hose or fuel tank vapor line.
Faulty or erratic fuel level sensor.
Faulty or erratic fuel tank pressure sensor.
Faulty EVAP canister purge valve.
Faulty EVAP canister vent solenoid.
Faulty EVAP tank pressure control solenoid valve.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, clear DTCs. Start engine. Operate engine for one minute and check for DTCs. Is there a current or pending DTC P0443 set, go to next step. If there is no current or pending DTC P0443, see «DIAGNOSTIC AIDS»(ref-99188-S35867827382001062700000) .
Turn ignition off. Disconnect EVAP canister purge valve harness connector. Using a DVOM, check resistance of EVAP canister purge valve. If resistance is 28-36 ohms at 68°F (20°C), go to next step. If resistance is not 28-36 ohms at 68°F (20°C), go to step 8 .
Turn ignition on, with engine off. Using test light connected to ground, probe EVAP canister purge valve harness connector terminal No. 1 (Blue/Black wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 7 .
Reconnect EVAP canister purge valve harness connector. Using test light connected to battery voltage, backprobe EVAP canister purge valve harness connector terminal No. 2 (Green/Black wire). Using scan tool, command EVAP canister purge valve on. Adjust duty cycle from zero to 100 percent while observing test light. If test light flashes, then stay on when 100 percent duty cycle is reached, go to step 8 . If test light does not flash or stay on when 100 percent duty cycle is reached, go to next step.
Turn ignition off. Check for open or short in Green/Black wire between EVAP canister purge valve and PCM. Repair as necessary. After repairs, go to step 10 . If circuit is okay, go to step 9 .
Turn ignition off. Repair open in Blue/Black wire between EVAP canister purge valve and main relay. After repairs, go to step 10 .
Replace EVAP canister purge valve. After replacing purge valve, go to step 10 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine an operate vehicle within the conditions for running the DTC or until DTC P0443 diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S13866326022001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are displayed, system is okay.

If both DTCs P0440 and P0443 are set, most likely cause is an inoperable EVAP canister purge valve. Check EVAP canister purge valve for poor connections and erratic operation. DTC P0443 is most likely to set during city driving. Avoid operating vehicle on the highway to validate DTC P0443. Check the following and repair as necessary

Cracked or punctured EVAP canister.
Damaged or disconnect source vacuum line, EVAP purge line, vent hose or fuel tank vapor line.
Plugged, restricted, leaking or damaged EVAP canister.
Damaged wiring harness.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Turn ignition off. Remove fuel filler cap. Turn ignition on, with engine off. Observe FTP sensor parameter on scan tool. If scan tool displays 0.0-0.5 in. H 2 O (0.0-0.9 mm Hg), go to step 11. If scan tool does not display 0.0-0.5 in. H 2 O (0.0-0.9 mm Hg), go to next step.
Turn ignition off. Remove fuel tank. Remove FTP sensor from fuel tank. Visually inspect FTP sensor air vent hole and air pressure inlet passage for blockage. If blockage exists, go to step 13. If blockage does not exist, go to next step.
Disconnect FTP sensor harness connector. Turn ignition on, with engine off. Using DVOM, check voltage at FTP sensor harness connector terminal No. 3 (Gray/Yellow wire). see scheme 10 If voltage reading is 5 volts, go to step 6. If voltage reading is not 5 volts, go to next step.
Turn ignition off. Check for open in Gray/Yellow wire between FTP sensor and PCM. Repair as necessary. After repairs, go to step 18. If circuit is okay, go to step 14.
Using a test light connected to battery voltage, probe FTP sensor harness connector terminal No. 1 (Gray/Yellow wire). If test light illuminates, go to step 8. If test light does not illuminate, go to next step.
Check for open in Gray/Yellow wire between FTP sensor and PCM. Repair as necessary. After repairs, go to step 18. If circuit is okay, go to step 14.
Using a DVOM, select DC voltage scale. Reconnect FTP sensor harness connector. Using DVOM connected to ground, backprobe FTP sensor harness connector terminal No. 1 (Brown/Red wire). If voltage reading is 2.5-2.7 volts, leave DVOM connected and go to next step. If voltage reading is not 2.5-2.7 volts, go to step 15.
Apply a small amount of vacuum to FTP sensor while observing DVOM. If voltage drops, go to next step. If voltage does not drop, go to step 16.
Check for open in Brown/Red wire on 2.0L or Red/Green wire on 2.5L between FTP sensor and PCM. Repair as necessary. After repairs, go to step 18. If circuit is okay, go to step 14.
Remove FTP control valve. Blow air through valve from canister port (some resistance should be present). If air escapes from fuel tank port, go to next step. If air does not escape from tank port, go to step 17.
Blow hard through fuel tank port of FTP control valve. Air should escape from canister port. Apply 15 in. Hg of vacuum to vacuum port of fuel tank pressure control valve. With vacuum applied, blow gently through fuel tank port. Air should escape easily through canister port. If fuel tank pressure control valve operates as described, see «DIAGNOSTIC AIDS»(ref-99188-S34516393282001062700000). If fuel tank pressure control valve does not operate as described, go to step 17.
Clean FTP sensor air passages. After repairs, go to step 18.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to step 18.
Check for short in Brown/Red wire between FTP sensor and PCM. Repair as necessary. After repairs, go to step 18. If circuit is okay, go to next step.
Replace FTP sensor. After replacing FTP sensor, go to step 18.
Replace FTP control valve. After replacing FTP control valve, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine an operate vehicle within the conditions for running the DTC or until DTC P0450 diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S40590917632001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no other DTCs are displayed, system is okay.

Check and repair plugged sensor air vent hole. If multiple DTCs are set, reference voltage circuit may be open or shorted, or ground circuit may be open.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Turn ignition off. Remove fuel filler cap. Turn ignition on, with engine off. Using scan tool, select FTP sensor parameter. If pressure is within 0.0-0.5 in. H2O (0.0-0.9 mm Hg), go to step 11 . If pressure is not within 0.0-0.5 in. H2O (0.0-0.9 mm Hg), go to next step.
Turn ignition off. Remove fuel tank. Remove FTP sensor from fuel tank. Check sensor air vent hole and air pressure inlet passage for clogging. If any problem is found, go to step 13 . If no problem is found, go to next step.
Disconnect FTP sensor harness connector. Turn ignition on, with engine off. Using a DVOM, check voltage on FTP sensor harness connector terminal No. 3 (Gray/Red wire). If voltage reading is 5 volts, go to step 6 . If voltage reading is not 5 volts, go to next step.
Turn ignition off. Check for open in Gray/Red wire between FTP sensor and PCM. Repair as necessary. After repairs, go to step 18 . If circuit is okay, go to step 14 .
Using a test light connected to battery voltage, probe FTP sensor harness connector terminal No. 2 (Gray/Yellow wire). If test light illuminates, go to step 8 . If test light does not illuminate, go to next step.
Turn ignition off. Check for open in Gray/Yellow wire between FTP sensor and PCM. Repair as necessary. After repairs, go to step 18 . If circuit is okay, go to step 14 .
Reconnect FTP sensor harness connector. Using a DVOM connected to ground, backprobe FTP sensor harness connector terminal No. 1 (Brown/Red wire). If voltage reading is 2.5-2.7 volts, go to next step. If voltage reading is not 2.5-2.7 volts, go to step 15 .
Apply a small amount of vacuum to FTP sensor while observing DVOM. If voltage decreases when vacuum is applied, go to next step. If voltage does not decrease when vacuum is applied, go to step 16 .
Check for open in Brown/Red wire between sensor and PCM. Repair as necessary. After repairs, go to step 18 . If circuit is okay, go to step 14 .
Remove FTP control valve. Connect a vacuum hose to canister side port of FTP control valve. Blow air into hose on FTP control valve (some resistance should be present). If air flows through the valve to the tank port side, go to next step. If does not flow through the valve to the tank port side, go to step 17 .
Connect a hose to fuel tank port of FTP control valve. From the tank side port, blow hard through the valve. Air should flow through the valve out of the canister port. If FTP control valve passes this test, see «DIAGNOSTIC AIDS»(ref-99188-S19427834352001062900000) . If FTP control valve does not pass this test, go to step 17 .
Clean sensor orifice. After cleaning orifice, go to step 18 .
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to step 18 .
Turn ignition off. Check for short in Brown/Red wire between FTP sensor and PCM. Repair as necessary. After repairs, go to step 18 . If circuit is okay, go to next step.
Turn ignition off. Replace FTP sensor. After replacing sensor, go to step 18 .
Turn ignition off. Replace FTP control valve. After replacing control valve, go to next step.
Clear DTCs. On 2.0L, turn ignition off. Remove DOME fuse for 30 seconds. Reinstall fuse. Reset radio clock time. On 2.5L, turn ignition on with engine off. Use scan tool to clear DTCs. Turn ignition off for 30 seconds. On all models, start engine and operate vehicle within the conditions for running the DTC or until DTC P0451 diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S06387352112001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are displayed, system is okay.

Check for a skewed fuel tank pressure sensor. Compare voltage readings with a known-good sensor. Check for a plugged sensor air vent hole and clean if necessary.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Check harness connectors for backed-out terminal, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Retrieve DTCs. If DTC P0443, P0440, P0445 or P0450 is also set, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If DTC P0443, P0440, P0445 or P0450 is not set, go to next step.
Turn ignition off. Remove fuel filler cap. Turn ignition on, with engine off. Observe FTP sensor parameter on scan tool. If scan tool displays 0.0-0.5 in. H2O (0.0-0.9 mm Hg), go to step 12 . If scan tool does not display 0.0-0.5 in. H2O (0.0-0.9 mm Hg), go to next step.
Turn ignition off. Remove fuel tank. Remove FTP sensor from fuel tank. Visually inspect FTP sensor air vent hole and air pressure inlet passage for blockage. If blockage exists, go to step 21 . If blockage does not exist, go to next step.
Turn ignition on, with engine off. Disconnect FTP sensor harness connector. Using DVOM, check voltage at FTP sensor harness connector terminal No. 3 (Gray/Red wire). If voltage reading is 5 volts, go to step 7 . If voltage reading is not 5 volts, go to next step.
Turn ignition off. Check for open or short in Gray/Red wire between FTP sensor and PCM. Repair as necessary. After repairs, go to step 29 . If circuit is okay, go to step 25 .
Using a test light connected to battery voltage, probe FTP sensor harness connector terminal No. 2 (Gray/Yellow wire). If test light illuminates, go to step 9 . If test light does not illuminate, go to next step.
Turn ignition off. Check for open in Gray/Yellow wire between FTP sensor and PCM. Repair as necessary. After repairs, go to step 29 . If circuit is okay, go to step 25 .
Using a DVOM, select DC voltage scale. Reconnect FTP sensor harness connector. Using DVOM connected to ground, backprobe FTP sensor harness connector terminal No. 1 (Brown/Red wire). If voltage reading is 2.0-2.5 volts, leave DVOM connected and go to next step. If voltage reading is not 2.0-2.5 volts, go to step 26 .
Apply a small amount of vacuum to FTP sensor while observing DVOM. If voltage drops, go to next step. If voltage does not drop, go to step 27 .
Check for open in Brown/Red wire between FTP sensor and PCM. Repair as necessary. After repairs, go to step 29 . If circuit is okay, go to step 25 .
Remove FTP control valve. Blow air through valve from canister port (some resistance should be present). If air escapes from fuel tank port, go to next step. If air does not escape from tank port, go to step 28 .
Blow hard through fuel tank port of FTP control valve. Air should escape from canister port. Apply 15 in. Hg of vacuum to vacuum port of FTP control valve. With vacuum applied, blow gently through fuel tank port. Air should escape easily through canister port. If FTP control valve operates as described, go to next step. If FTP control valve does not operate as described, go to step 28 .
Turn ignition off. Disconnect vacuum hose from EVAP canister vent solenoid canister port. Apply 15 in. Hg of vacuum to EVAP canister vent solenoid canister port. If solenoid holds vacuum, go to step 22 . If solenoid does not hold vacuum, go to next step.
Turn ignition on, with engine off. Using scan tool, command EVAP canister vent solenoid on. Apply 15 in. Hg of vacuum to EVAP canister vent solenoid canister port. If solenoid holds vacuum, go to next step. If solenoid does not hold vacuum, go to step 17 .
While EVAP canister vent solenoid is holding vacuum, use scan tool to command solenoid off. If vacuum is released, see «DIAGNOSTIC AIDS»(ref-99188-S14498921012001062700000) . If vacuum is not released, go to step 24 .
Turn ignition off. Disconnect EVAP canister vent solenoid harness connector. Turn ignition on, with engine off. Using a test light connected to ground, probe EVAP canister vent solenoid harness connector terminal No. 1 (Blue/Black wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 19 .
Using scan tool, command EVAP canister vent solenoid on. Using a test light connected to battery voltage, probe EVAP canister vent solenoid harness connector terminal No. 2 (Purple/Red wire). If test light illuminates, go to step 23 . If test light does not illuminate, go to step 20 .
Turn ignition off. Repair open or short in Blue/Black wire between main relay and EVAP canister vent solenoid. After repairs, go to step 29 .
Turn ignition off. Check for open in Purple/Red wire between EVAP canister vent solenoid and PCM. Repair as necessary. After repairs, go to step 29 . If circuit is okay, go to step 25 .
Clean FTP sensor air passage. After repairs, go to step 29 .
Check EVAP canister vent solenoid vacuum hoses for restriction. Repair as necessary. After repairs, go to step 29 . If vacuum hoses are okay, go to next step.
Turn ignition off. Replace EVAP canister vent solenoid. After replacing solenoid, go to step 29 .
Check for short to ground in Purple/Red wire between EVAP canister vent solenoid and PCM. Repair as necessary. After repairs, go to step 29 . If circuit is okay, go to next step.
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to step 29 .
Turn ignition off. Check for a short in Brown/Red wire between FTP sensor and PCM. Repair as necessary. After repairs, go to step 29 . If circuit is okay, go to next step.
Turn ignition off. Replace FTP sensor. After replacing sensor, go to step 29 .
Replace FTP control valve. After replacing fuel tank pressure control valve, go to next step.
Turn ignition on, with engine off. Using scan too, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for running the DTC. See «CODE ENABLE CRITERIA»(ref-99188-S18148782402001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are displayed, system is okay.

Check the following and repair as necessary

Shifted (incorrectly calibrated) FTP sensor may cause DTC P0451 to set.
Plugged sensor air vent hole.
If DTCs P0108, P0113, P0118, P0123 and P0450 are set together, check for an open ground circuit.
If DTCs P0107, P0122 and P0450 are set together, check for an open reference circuit.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
If any EVAP DTCs are set other than DTC P0440 or P0455, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other EVAP DTCs are set, go to next step.
Using scan tool, observe Fuel Tank Pressure (FTP) sensor parameter. Remove fuel filler cap. If FTP sensor parameter is 0.0-0.5 in. H2O (0.0-0.9 mm Hg) with fuel filler cap removed, go to next step. If FTP sensor parameter is not 0.0-0.5 in. H2O (0.0-0.9 mm Hg) with fuel filler cap removed, go to «DTC P0450»(ref-99188-S03272130892001062700000) .
Turn ignition off. Visually inspect the entire EVAP control system for loose hose connections, damaged or deteriorated hoses, clogged hoses, missing or damaged components, or loose or incorrect fuel filler cap. If a problem is found, go to step 16 . If no problem is found, go to next step.
Turn ignition on, with engine off. Remove fuel cap and install gas cap adapter. Connect EVAP Pressure/Purge Diagnostic Station (J-41413) to gas cap adapter. Using scan tool, command EVAP canister vent valve on. Pressurize EVAP system to 15 in. H2O (28 mm Hg) using the diagnostic station. Monitor pressure using gauge on diagnostic station. Turn rotary switch on diagnostic station to HOLD position and observe EVAP pressure gauge. If pressure decreases to less than 10 in. H2O (18.6 mm Hg) within 2 minutes, go to next step. If pressure does not decreases to less than 10 in. H2O (18.6 mm Hg) within 2 minutes, go to step 8 .
Continuously attempt to pressurize EVAP system to 30 in. H2O (56 mm Hg). Using an Ultrasonic Leak Detector (J-41416), locate any leaks in EVAP system. Partially lower fuel tank in order to examine the top tank connections. If any leaks were found, go to next step. If no leaks were found, go to step 8 .
Repair or replace any leaking or faulty EVAP control system components. After repairs, go to step 30 .
Turn ignition off. Check EVAP canister purge valve for manifold vacuum from intake manifold vacuum port, leaking or damaged vacuum hoses, or restricted vacuum hoses or passages. Repair as necessary. After repairs, go to step 30 . If no problem is found, go to next step.
Turn ignition on, with engine off. Disconnect vacuum hoses to EVAP canister purge valve from intake manifold and from EVAP canister. Blow air into vacuum hose that was disconnected from EVAP canister. Air should not pass through EVAP canister purge valve and exit from intake manifold hose. Using scan tool, command EVAP canister purge valve on and adjust duty cycle to 100 percent. Blow air into vacuum hose that was disconnected from EVAP canister. Air should pass through EVAP canister purge valve and exit from intake manifold hose. If EVAP canister purge valve passes both inspections, go to step 12 . If EVAP canister purge valve does not pass both inspections, go to next step.
Using test light connected to ground, probe EVAP canister purge valve harness connector terminal No. 1 (Blue/Black wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 20 .
Connect test light to battery voltage and probe EVAP canister purge valve harness connector terminal No. 2 (Green/Black wire). Using scan tool, command EVAP canister purge valve on. Adjust duty cycle from 0 to 100 percent while monitoring test light. If test light flashes and then stay on as duty cycle reaches 100 percent, go to step 28 . If test light does not flash and then stay on as duty cycle reaches 100 percent, go to step 27 .
Turn ignition off. Remove EVAP canister vent valve. Blow air into EVAP canister vent valve port, located on side that was connected to EVAP canister air filter. If air passes through to other side of EVAP canister vent valve, go to next step. If air does not pass through to other side of EVAP canister vent valve, go to step 25 .
Turn ignition on, with engine off. Using scan tool, command EVAP canister vent valve on. Blow air into EVAP canister vent valve port, located on side that was connected to EVAP canister air filter. If air does not pass through the EVAP canister vent valve, go to next step. If air passes through the EVAP canister vent valve, go to step 15 .
Continue to blow air into EVAP canister vent valve. Using scan tool, command EVAP canister vent valve off. If air passes through EVAP canister vent valve when scan tool commanded the vent valve off, go to step 17 . If air does not pass through EVAP canister vent valve when scan tool commanded the vent valve off, go to step 21 .
Turn ignition off. Disconnect EVAP canister vent valve harness connector. Turn ignition on, with engine off. Using test light connected to ground, probe EVAP canister vent solenoid harness connector terminal No. 1 (Blue/Black wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 20 .
Turn ignition off. Using scan tool, command EVAP canister vent solenoid on. Using test light connected to battery voltage, probe EVAP canister vent solenoid harness connector terminal No. 2 (Purple/Red wire). If test light illuminates, go to step 25 . If test light does not illuminate, go to step 23 .
Disconnect EVAP canister vacuum/vapor hoses. Blow air into tank port of EVAP canister. There should be no restriction of air flow through the canister and out the purge pipe and air port. If EVAP canister passes this test, go to next step. If EVAP canister does not pass this test, go to step 22 .
Remove FTP control valve. Connect a vacuum hose to canister side port of FTP control valve, some resistance should be felt, but air should flow steadily. Blow air into hose on FTP control valve. If air flows through the valve to the tank port side, go to next step. If air does not flow through the valve to the tank port side, go to step 26 .
Move the vacuum hose to fuel tank port of FTP control valve. Blow hard into hose connected to tank port side of FTP control valve. Air should flow easily through the valve and out of canister port. If FTP control valve passes this test, go to step 24 . If FTP control valve does not pass this test, go to step 26 .
Turn ignition off. Repair open in Blue/Black wire. After repairs, go to step 30 .
Turn ignition off. Check for short to ground in Purple/Red wire between EVAP canister vent solenoid and PCM. Repair as necessary. After repairs, go to step 30 . If circuit is okay, go to step 29 .
Turn ignition off. Replace EVAP canister. After replacing EVAP canister, go to step 30 .
Turn ignition off. Check for open in Purple/Red wire . Repair as necessary. After repairs, go to step 30 . If circuit is okay, go to step 29 .
Check EVAP canister air filter and hoses for restrictions or blockage. Repair as necessary. After repairs, go to step 30 . If no problem is found, see «DIAGNOSTIC AIDS»(ref-99188-S41264861592001063000000) .
Replace EVAP canister vent solenoid. After replacing vent solenoid, go to step 30 .
Turn ignition off. Replace FTP control valve. After replacing control valve, go to step 30 .
Turn ignition off. Check for open or short in Green/Black wire between EVAP canister purge valve and PCM. Repair as necessary. After repairs, go to step 30 . If circuit is okay, go to step 29 .
Turn ignition off. Replace EVAP canister purge valve. After replacing canister purge valve, go to step 30 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within FREEZE FRAME conditions that set DTC. If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are displayed, system is okay.

An incorrect type fuel filler cap, a cracked or punctured EVAP canister, damaged or disconnected source vacuum line, EVAP purge line, vent hose, fuel tank vapor line, faulty or erratic fuel tank pressure sensor can cause DTC to set.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
If any other EVAP DTCs are set except P0440, affected diagnose DTCs. If no other EVAP DTCs are set, go to next step.
Turn ignition off. Visually inspect entire EVAP control system for loose hose connections, damaged or deteriorated hoses, clogged hoses, missing or damaged components, poor wiring harness connections, or loose or faulty fuel filler cap. If a problem is found, go to step 21 . If no problems is found, go to next step.
Remove FTP control valve. Blow air through valve from canister port (some resistance should be present). If air escapes from fuel tank port, go to next step. If air does not escape from fuel tank port, go to step 29 .
Blow hard through fuel tank port of FTP control valve. Air should escape from canister port. Apply 15 in. Hg of vacuum to vacuum port of FTP control valve. With vacuum applied, blow gently through fuel tank port. Air should escape easily through canister port. If FTP control valve operates as described, go to next step. If FTP control valve does not operate as described, go to step 29 .
Turn ignition on, with engine off. Using scan tool, command EVAP tank pressure control solenoid vacuum valve on. Disconnect vacuum hoses from EVAP tank pressure control solenoid vacuum valve. Blow air through FTP control valve port of EVAP tank pressure control solenoid vacuum valve. If air escapes from vacuum port, go to next step. If air does not escape from vacuum port, go to step 8 .
Turn ignition off. Check vacuum hoses and intake manifold port for leaks, cracks or blockage. Repair as necessary. After repairs, go to step 35 . If vacuum hoses and intake manifold port are okay, go to step 10 .
Turn ignition off. Disconnect EVAP tank pressure control solenoid valve vacuum valve harness connector. Turn ignition on, with engine off. Using a test light connected to ground, probe EVAP tank pressure control solenoid valve harness connector terminal No. 1 (Blue/Black wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 23 .
Using a test light connected to battery voltage, probe EVAP tank pressure control solenoid valve harness connector terminal No. 2 (Green/White wire). Using scan tool, command EVAP tank pressure control solenoid vacuum valve on and off, while observing test light. Test light should illuminate when EVAP pressure control solenoid vacuum valve is on, and should not illuminate when off. If test light illuminates as described, go to step 33 . If test light does not illuminate as described, go to step 32 .
Check EVAP canister purge valve for manifold vacuum at intake manifold vacuum port, leaking or damaged vacuum hoses, or clogged or restricted vacuum hoses or passages. Repair as necessary. After repairs, go to step 35 . If no problem is found, go to next step.
Disconnect EVAP canister purge valve vacuum hoses from intake manifold and EVAP canister. Blow air into vacuum hose that was disconnect from EVAP canister. Air should not escape from disconnected intake manifold vacuum hose. Using scan tool, command EVAP canister purge valve on and adjust duty cycle to 100 percent. Blow air into vacuum hose that was disconnected from EVAP canister. Air should now escape from disconnected intake manifold vacuum hose. If EVAP canister purge valve operated as described, go to step 14 . If EVAP canister purge valve does not operate as described, go to next step.
Using a test light connected to ground, probe EVAP canister purge valve harness connector terminal No. 1 (Blue/Black wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 23 .
Using a test light connected to battery voltage, probe EVAP canister purge valve harness connector terminal No. 2 (Green/Black wire). Using scan tool, command EVAP canister purge valve on and adjust duty cycle from zero to 100 percent, while observing test light. If test light flashes, and then illuminates steady when 100 percent duty cycle is reached, go to step 31 . If test light does not flash, and then illuminate steady when 100 percent duty cycle is reached, go to step 30 .
Turn ignition off. Remove EVAP canister vacuum hose from EVAP canister vent solenoid. Apply 15 in. Hg of vacuum to EVAP canister side of EVAP canister vent solenoid. If solenoid holds vacuum, go to step 27 . If solenoid does not hold vacuum, go to next step.
Turn ignition on, with engine off. Using scan tool, command EVAP canister vent solenoid on. Apply 15 in. Hg of vacuum to EVAP canister side of EVAP canister vent solenoid. If solenoid holds vacuum, go to next step. If solenoid does not hold vacuum, go to step 17 .
With vacuum still applied, use scan tool to command EVAP canister vent solenoid off. If vacuum is released, go to step 19 . If vacuum is not released, go to step 24 .
Turn ignition off. Disconnect EVAP canister vent solenoid harness connector. Turn ignition on, with engine off. Using a test light connected to ground, probe EVAP canister vent solenoid harness connector terminal No. 1 (Blue/Black wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 23 .
Using scan tool, command EVAP canister vent solenoid on. Using a test light connected to battery voltage, probe EVAP canister vent solenoid harness connector terminal No. 2 (Purple/Red wire). If test light illuminates, go to step 28 . If test light does not illuminate, go to step 26 .
Remove fuel filler cap and install Gas Cap Adapter (J-41415-30). Connect Pressure/Purge Diagnostic Station (J-41413-EVAP) to gas cap adapter. Apply 15 in. Hg of vacuum to EVAP tank pressure control solenoid valve vacuum port. Using scan tool, command EVAP canister vent solenoid on. Using EVAP pressure/purge diagnostic station, pressurize fuel tank to 15 in. H2O (28 mm Hg). Turn rotary switch on EVAP pressure/purge diagnostic station to HOLD position and observe EVAP pressure gauge. If EVAP pressure gauge decreases to 10 in. H2O (18.6 mm Hg) or less within 2 minutes, go to next step. If EVAP pressure gauge does not decrease to 10 in. H2O (18.6 mm Hg) or less within 2 minutes, go to step 22 .
With condition met in previous step, continue to pressurize fuel tank to 30 in. H2O (56 mm Hg). With tank pressurized, check EVAP system for leaks using Ultrasonic Leak Detector (J-41416). If leaks exist, go to next step. If no leaks exist, go to step 22 .
Repair leaks and/or replace any faulty components as necessary. After repairs, go to step 35 .
Disconnect vacuum hoses from EVAP canister and plug EVAP canister vent solenoid port. Connect vacuum pump to EVAP canister tank port. Attempt to obtain 10 in. H2O (18.6 mm Hg) of vacuum. If EVAP canister holds vacuum, go to step 25 . If EVAP canister does not hold vacuum, see «DIAGNOSTIC AIDS»(ref-99188-S37864706532001062700000) .
Turn ignition off. Repair open in Blue/Black wire between main relay and EVAP component. After repairs, go to step 35 .
Turn ignition off. Check for short to ground in Purple/Red wire between PCM and EVAP canister vent solenoid. Repair as necessary. After repairs, go to step 35 . If circuit is okay, go to step 34 .
Turn ignition off. Replace EVAP canister. After replacing EVAP canister, go to step 35 .
Turn ignition off. Check for open in Purple/Red wire between PCM and EVAP canister vent solenoid. Repair as necessary. After repairs, go to step 35 . If circuit is okay, go to step 34 .
Check EVAP canister vent solenoid vacuum hoses for restriction. Repair as necessary. After repairs, go to step 35 . If vacuum hoses are okay, go to next step.
Turn ignition off. Replace EVAP canister vent solenoid. After replacing canister vent solenoid, go to step 35 .
Replace FTP pressure control valve. After replacing FTP control valve, go to step 35 .
Turn ignition off. Check for open or short in Green/Black wire between PCM and EVAP canister purge valve. Repair as necessary. After repairs, go to step 35 . If circuit is okay, go to step 34 .
Turn ignition off. Replace EVAP canister purge valve. After replacing EVAP canister purge valve, go to step 35 .
Turn ignition off. Check for open or short in Green/White wire between PCM and EVAP tank pressure control solenoid valve. Repair as necessary. After repairs, go to step 35 . If circuit is okay, go to step 34 .
Turn ignition off. Replace EVAP tank pressure control solenoid valve. After replacing EVAP tank pressure control solenoid valve, go to step 35 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within FREEZE FRAME conditions that set DTC. If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are displayed, system is okay.

DTC is most likely to set during city driving. Avoid operating vehicle for long periods of time on the highway to validate DTC. Check for loose or missing fuel filler cap, cracked or punctured EVAP canister, damaged or disconnect source vacuum line, EVAP purge line, vent hose or fuel tank vapor line, faulty or erratic fuel tank pressure sensor. Repair as necessary.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Turn ignition off. Check for stuck or binding throttle valve, accelerator cable, or accelerator pedal. Check for vacuum or intake air leaks. Check for EGR or EVAP system malfunction. Check for faulty or Incorrect TP sensor, ECT sensor, or MAF sensor input. Repair as necessary. After repairs, go to step 5. If no problem is found, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Start and operate engine for one minute. Recheck for DTCs. If a current or pending DTC P0505 is set, go to step 7. If no current or pending DTC is set, go to next step.
Warm engine to normal operating temperature. Using scan tool, select RPM CONTROL under IAC system in SPECIAL FUNCTIONS menu. Command IAC valve to increase and decrease engine speed. If engine speed increases and decreases when commanded by scan tool, go to next step. If engine speed does not increase or decrease when commanded by scan tool, go to step 7.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions or until DTC P0505 diagnostic test has run. If DTC P0505 resets, go to step 7. If DTC P0505 does not reset, go to next step.
Start engine. Turn off all accessories. Warm engine to normal operating temperature. Observe engine speed and IAC duty cycle parameters on scan tool. If engine speed is within 700-800 RPM in Park or Neutral, and IAC duty cycle is at 10-30 percent, system is okay. If engine speed is not within 700-800 RPM in Park or Neutral, and IAC duty cycle is not at 10-30 percent, diagnose idle problem. See appropriate TROUBLE SHOOTING - NO CODES article.
Turn ignition off. Disconnect IAC valve harness connector. Turn ignition on, with engine off. Using a test light connected to ground, probe both IAC valve harness connector terminals No. 2 (Blue/Black wire) and No. 5 (Blue/Black wire). see scheme 11 If test light illuminated on both circuits, go to next step. If test light did not illuminate on both circuits, go to step 11.
Disconnect IAC valve harness connector. Using DVOM, check resistance of IAC valve coil windings. Check between IAC valve terminals No. 1 and 2, terminals No. 2 and 3, terminals No. 5 and 6, and terminals No. 4 and 5. If resistance is 35-43 ohms at 68°F (20°C), go to next step. If resistance is not 35-43 ohms at 68°F (20°C), go to step 14.
Turn ignition off. Reconnect IAC valve harness connector. Disconnect PCM harness connector C4. Turn ignition on, with engine off. On 2.0L, check voltage at PCM harness connector C4 terminals No. 3 (Light Green/Black wire), No. 10 (Purple/Yellow wire), No. 11 (Gray/Blue wire) and No. 12 (Purple/Black wire). On 2.5L, check voltage at PCM harness connector C4 terminals No. 14 (Purple/Black wire), No. 15 (Light Green/Black wire), No. 24 (Purple/Yellow wire) and No. 25 (Gray/Blue wire). see scheme 3or see scheme 4. If voltage reading of each IAC coil control circuit is greater than 12 volts, go to next step. If voltage reading of each IAC coil control circuit is not greater than 12 volts, go to step 12.
Turn ignition off. Reconnect PCM harness connector. Start and warm engine to normal operating temperature. On 2.0L, using a DVOM connected to ground, backprobe PCM harness connector C4 terminals No. 3 (Light Green/Black wire), No. 10 (Purple/Yellow wire), No. 11 (Gray/Blue wire), and No. 12 (Purple/Black wire). see scheme 3 On 2.5L, using a DVOM connected to ground, backprobe PCM harness connector C4 terminals No. 14 (Purple/Black wire), No. 15 (Light Green/Black wire), No. 24 (Purple/Yellow wire), and No. 25 (Gray/Blue wire). see scheme 3 Observe voltage display on DVOM for each control circuit while increasing and decreasing engine speed using scan tool in RPM control function mode. If voltage of each IAC coil control circuit is switching from high to low while increasing and decreasing engine speed, go to step 13. If voltage of each IAC coil control circuit is not switching from high to low while increasing and decreasing engine speed, go to step 15.
Turn ignition off. Repair high resistance or open Blue/Black wire. After repairs, go to step 16.
Turn ignition off. Repair short to ground, open circuit, or high resistance in any IAC valve circuit that did not measure at least 12 volts. After repairs, go to step 16.
Remove IAC valve. Check idle air bypass passage for restrictions or blockage. After repairs, go to step 16. If passages are okay, go to next step.
Replace IAC valve. After replacing IAC valve, go to step 16.
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within conditions for running the DTC. See «CODE ENABLE CRITERIA»(ref-99188-S09354237082001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no other DTCs are displayed, system is okay.

Check and repair the following as necessary

Binding, leaking or damaged throttle valve.
Air leak into intake air supply.
Restricted air intake system. Check for collapsed air intake duct, restricted air filter element, or foreign objects blocking air intake system.
Throttle body for excessive carbon deposits in IAC air passage or on IAC pintle.
Throttle body for excessive carbon deposits in throttle bore or on throttle plate of throttle body assembly.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, clear DTCs. Turn ignition off to initialize PCM. Start engine. Road test vehicle. Recheck for DTCs. If this DTC resets, go to next step. If this DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S38405406022001062700000) .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within conditions for running the DTC. See «CODE ENABLE CRITERIA»(ref-99188-S24929834132001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are displayed, system is okay.

Check PCM for water contamination. Water in PCM can cause damage and corrosion to circuit boards and to internal components. Repair source of water intrusion before installing a new PCM.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, clear DTCs. Turn ignition off to initialize PCM. Start engine. Road test vehicle. Recheck for DTCs. If this DTC resets, go to next step. If this DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S38405406022001062700000) .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within conditions for setting the DTC. See «CODE ENABLE CRITERIA»(ref-99188-S11317678532001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are displayed, system is okay.

Check PCM for water contamination. Water in PCM can cause damage and corrosion to circuit boards and to internal components. Repair source of water intrusion before installing a new PCM.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Apply parking brake. Using scan tool, monitor transmission range switch status with transmission in Park. If scan tool shows that transmission is in Park, go to next step. If scan tool does not show than transmission is in Park, go to step 9 .
Shift transmission to Reverse position. Monitor transmission range switch status on scan tool with transmission in Reverse. If scan tool shows that transmission is in Reverse, go to next step. If scan tool does not show transmission is in Reverse, go to step 9 .
Shift transmission to Neutral position. Monitor transmission range switch status on scan tool with transmission in Neutral. If scan tool shows that transmission is in Neutral, go to next step. If scan tool does not show that transmission is in Neutral, go to step 9 .
Shift transmission to Drive position. Monitor transmission range switch status on scan tool with transmission in Drive. If scan tool shows that transmission is in Drive, go to next step. If scan tool does not show that transmission is in Drive, go to step 9 .
Shift transmission to 2nd gear position. Monitor transmission range switch status on scan tool with transmission in 2nd gear. If scan tool shows that transmission is in 2nd gear, go to next step. If scan tool does not show that transmission is in 2nd gear, go to step 9 .
Shift transmission to Low position. Monitor transmission range switch status on scan tool with transmission in Low. If scan tool shows that transmission is in Low, go to next step. If scan tool does not show that transmission is in Low, go to step 9 .
Problem is intermittent. Check for out of adjustment transmission range switch or switch malfunction. Check for faulty electrical circuits. If a problem is found, repair as necessary. After repairs or if no problem is found, go to step 14 .
Turn ignition switch to LOCK position. Disconnect PCM harness connector C3. Turn ignition switch on. Shift transmission to the gear position that failed. Check voltage at PCM harness connector terminal that failed the functional test. If voltage reading is 10-14 volts, go to next step. If voltage reading is not 10-14 volts, go to step 11 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition switch to LOCK position. Disconnect transmission range switch harness connector. Check resistance between the failed PCM harness connector terminals and corresponding transmission range switch harness connector terminals. If resistance is within 2 ohms, go to next step. If resistance is not within 2 ohms, go to step 13 .
Check transmission range switch for proper alignment. If alignment is okay, replace transmission range switch. After replacing range switch, go to step 14 .
Repair open or high resistance in circuit between transmission range switch and PCM. After repairs, go to next step.
Turn ignition switch to LOCK position. Reconnect any disconnected connector(s). Clear DTCs. Operate vehicle within FREEZE FRAME conditions that set DTC. Check for DTCs. If no DTCs are stored, go to next step. If any DTCs are stored, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are displayed, system is okay.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Start and warm engine to normal operating temperature. Operate engine at idle. Using DVOM, backprobe PCM harness connector C2 terminal No. 8 (Red/White wire) on 2.0L, or terminal No. 13 (Red/White wire) on 2.5L. see scheme 3 If voltage reading is 0.2-4.6 volts, go to next step. If voltage reading is not 0.2-4.6 volts, go to step 4.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If this DTC resets, go to next step. If this DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S00692674212001062700000).
Turn ignition off. Disconnect MAP sensor harness connector. Turn ignition on, with engine off. Using DVOM, check voltage at MAP sensor harness connector terminal No. 3 (White/Red wire on 2.0L or Gray/Red wire on 2.5L). If voltage reading is 5 volts, go to next step. If voltage reading is not 5 volts, go to step 8.
Using a test light connected to battery voltage, probe MAP sensor harness connector terminal No. 2 (Blue/White wire on 2.0L or Gray/Yellow wire on 2.5L). If test light illuminates, go to next step. If test light does not illuminate, go to step 9.
Turn ignition off. Check for open or short in Red/White wire between MAP sensor and PCM. Repair as necessary. After repairs, go to step 12. If circuit is okay, go to next step.
Reconnect MAP sensor harness connector. Turn ignition on, with engine off. Using DVOM, backprobe PCM harness connector C2 terminal No. 8 (Red/White wire) on 2.0L or terminal No. 13 (Red/White wire) on 2.5L. see scheme 3or see scheme 4. While observing DVOM, apply a small amount of vacuum to pressure passage at MAP sensor. If voltage drops, go to step 11. If voltage does not drop, go to step 10.
Turn ignition off. Check for open or short in MAP sensor in White/Red wire on 2.0L or Gray/Red wire on 2.5L between MAP sensor and PCM. Repair as necessary. After repairs, go to step 12. If circuit is okay, go to step 11.
Turn ignition off. Check for open or poor connection in Blue/White wire on 2.0L or Gray/Yellow wire on 2.5L between MAP sensor and PCM. Repair as necessary. After repairs, go to step 12. If circuit and connection are okay, go to step 11.
Turn ignition off. Replace MAP sensor. After replacing MAP sensor, go to step 12.
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for running the DTC. See «CODE ENABLE CRITERIA»(ref-99188-S37356429422001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no other DTCs are displayed, system is okay.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
If DTC P0461 or DTC P0463 is present, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If DTC P0461 or DTC P0463 is not present, go to next step.
Using scan tool, clear DTCs. Operate engine for one minute. If a current or pending DTC P1410 is set, go to next step. If there is no current or pending DTC P1410, see «DIAGNOSTIC AIDS»(ref-99188-S41142686852001062700000) .
Turn ignition off. Disconnect EVAP tank pressure control solenoid valve harness connector. Using DVOM, check resistance of EVAP tank pressure control solenoid valve. If resistance is 28-36 ohms at 68°F (20°C), go to next step. If resistance is not 28-36 ohms at 68°F (20°C), go to step 9 .
Turn ignition on, with engine off. Using a test light connected to ground, probe EVAP tank pressure control solenoid valve harness connector terminal No. 1 (Blue/Black wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 8 .
Using a test light connected to battery voltage, probe EVAP tank pressure control solenoid valve harness connector terminal No. 2 (Green/White wire). Using scan tool, command EVAP tank pressure control solenoid valve on. Observe test light. If test light illuminates when EVAP tank pressure control solenoid valve is commanded on, go to step 9 . If test light does not illuminate when EVAP tank pressure control solenoid valve is commanded on, go to next step.
Turn ignition off. Check for open or short to ground in Green/White wire. Repair as necessary. After repairs, go to step 11 . If circuit is okay, go to step 10 .
Turn ignition off. Repair open in Blue/Black wire. After repairs, go to step 11 .
Turn ignition off. Replace EVAP tank pressure control solenoid valve. After replacing solenoid valve, go to step 11 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for setting the DTC. See «CODE ENABLE CRITERIA»(ref-99188-S21139224552001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are displayed, system is okay.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If this DTC resets, go to next step. If this DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S28997145252001062700000) .
Turn ignition off. Check for short to ground in 5-volt reference circuit to MAP, TP and FTP sensors. Repair as necessary. After repairs, go to step 5 . If circuit is okay, go to next step.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for running the DTC. See «CODE ENABLE CRITERIA»(ref-99188-S28540533272001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are displayed, system is okay.

Barometric pressure varies depending on weather conditions and altitude.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Check DTCs. If DTC P1408 is set, diagnose DTC. Go to «DTC P1408»(ref-99188-S18638637132001062700000) . If DTC P1408 is not set, go to next step.
Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions. Retrieve DTCs. If this DTC resets, go to next step. If this DTC does not reset, see «DIAGNOSTIC AIDS»(ref-99188-S11700910712001062700000) .
Observe MAP sensor parameter on scan tool. If scan tool displays 100 kPa, go to next step. If scan tool does not display 100 kPa, see «DIAGNOSTIC AIDS»(ref-99188-S11700910712001062700000) .
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for running the DTC. See «CODE ENABLE CRITERIA»(ref-99188-S39176732172001101800000) . If DTC runs and passes, go to next step. If DTC resets, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000) . If no other DTCs are displayed, system is okay.

A malfunctioning or skewed MAP sensor may cause DTC P1451 to set. Barometric pressure varies depending on weather conditions and altitude.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Using scan tool, clear DTCs. Start engine and operate for 3 or more minutes. Observe MIL. If MIL is not illuminated, turn ignition off. Restart engine and operate for an additional 3 or more minutes. If DTC P1500 is set, go to next step. If DTC P1500 is not set, see «DIAGNOSTIC AIDS»(ref-99188-S17935636982001062700000).
Turn ignition off. Disconnect PCM harness connector C2 on 2.0L or C4 on 2.5L. Turn ignition on, with engine off. Place transmission in Neutral. Using DVOM, check voltage at PCM harness connector C2 terminal No. 18 (Black/Yellow wire) on 2.0L or connector C4 terminal No. 26 (Black/Yellow wire) on 2.5L. see scheme 3or see scheme 4. Fully depress clutch pedal. Crank engine and observe voltage on DVOM. If voltage reading is zero volts with ignition on and 6-12 volts with engine cranking, go to step 5. If voltage reading is not zero volts with ignition on and 6-12 volts with engine cranking, go to next step.
Turn ignition off. Repair open or short in Black/Yellow wire. After repairs, go to step 7.
Turn ignition off. Check for poor connections at PCM. Repair as necessary. After repairs, go to step 7. If connections are okay, go to next step.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for running the DTC. See «CODE ENABLE CRITERIA»(ref-99188-S10465083772001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no other DTCs are displayed, system is okay.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Start engine. Disconnect IAT sensor harness connector. Operate engine for at least one minute. Ensure MIL is illuminated. Reconnect IAT sensor harness connector. Turn ignition off. Wait one minute. Turn ignition on, with engine off. Using scan tool, check for DTCs. If DTC P0113 is set, see «DIAGNOSTIC AIDS»(ref-99188-S14164340562001062700000). If DTC P0113 is not set, go to next step.
Turn ignition off. Disconnect PCM harness connector C1. Using DVOM, check voltage between a known-good ground and PCM harness connector C1 terminal No. 2 (White wire). see scheme 3 If voltage reading is about battery voltage, go to step 5. If voltage reading is not about battery voltage, go to next step.
Turn ignition off. Check for open or short in White wire between PCM and fuse block. Repair as necessary. After repairs, go to step 7. If circuit is okay, see «DIAGNOSTIC AIDS»(ref-99188-S14164340562001062700000).
Check for poor connections at PCM. Repair as necessary. After repairs, go to step 7. If connections are okay, go to next step.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition off. Remove DOME fuse for 30 seconds (fuse is located in passenger compartment fuse block). Reinstall DOME fuse. Reset radio clock time. Start engine. Operate vehicle within the conditions for running the DTC or until DTC P01510 diagnostic test has run. See «CODE ENABLE CRITERIA»(ref-99188-S13344858382001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no other DTCs are displayed, system is okay.

PCM will indicate DTC P1510 as long as ignition is on. When ignition is turned off, PCM will lose memory of DTC P1510 and DTC will not be stored. Check for any blown fuses and replace as necessary.

Perform diagnostic system check. See «POWERTRAIN DIAGNOSTIC SYSTEM CHECK»(ref-99188-S42685789212001070200000) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
Start engine. Disconnect IAT sensor harness connector. Operate engine for at least one minute or until DTC P0113 sets. Reconnect IAT sensor harness connector. Turn ignition off. Wait for at least one minute. Turn ignition on, with engine off. Using scan tool, check for DTCs. If DTC P0113 is set, see «DIAGNOSTIC AIDS»(ref-99188-S40222325422001070200000). If DTC P0113 is not set, go to next step.
Turn ignition off. Using a DVOM connected to ground, backprobe PCM harness connector C1 terminal No. 35 (White wire). see scheme 4 If voltage reading is about battery voltage, go to step 5. If voltage reading is not about battery voltage, go to next step.
Check for open or short in White wire between PCM and fuse block No. 2. Repair as necessary. After repairs, go to step 7. If circuit is okay, see «DIAGNOSTIC AIDS»(ref-99188-S40222325422001070200000).
Check for poor connections at PCM. Repair as necessary. After repairs, go to step 7. If connections are okay, go to next step.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(ref-99188-S30982861452001070200000) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for running the DTC. See «CODE ENABLE CRITERIA»(ref-99188-S25569615582001101800000). If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-99188-S14830162302001070200000). If no other DTCs are displayed, system is okay.

PCM will indicate DTC P1510 as long as ignition is on. When ignition is turned off, PCM will lose memory of DTC P1510 and DTC will not be stored. Check for any blown fuses and replace as necessary.

Engine Control System Self-Diagnostics - 2.0L & 2.5L: Diagnosis Chevrolet Tracker II

ON-BOARD DIAGNOSTICS

Intermittent Trouble Code Determination

DIAGNOSTIC PROCEDURE

RETRIEVING DIAGNOSTIC TROUBLE CODES

Scheme 1

POWERTRAIN DIAGNOSTIC SYSTEM CHECK

CLEARING DIAGNOSTIC TROUBLE CODES

Scan Tool

SCAN TOOL USAGE

Diagnostic Procedures

Conditions For Running DTC

Diagnostic Aids

DIAGNOSTIC TROUBLE CODE DEFINITIONS

DIAGNOSTIC TESTS

More articles — Engine Control System Self-Diagnostics - 2.0L & 2.5L

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