Engine Control System - Self-Diagnostics: Diagnosis Pontiac Vibe I

ON-BOARD DIAGNOSTICS

Note. For more information on PCM operation, see THEORY & OPERATION - 1.8L VIBE article.

The Powertrain Control Module (PCM) diagnoses any troubles which may occur in the engine control system when the ignition switch is in the ON position with the engine running. The PCM indicates a malfunction by illuminating the Malfunction Indicator Light (MIL) when a fault occurs in any of the following systems

1. Heated Oxygen Sensor 1 (HO2S 1)
2. Heated Oxygen Sensor 2 (HO2S 2)
3. Engine Coolant Temperature (ECT) Sensor
4. Throttle Position (TP) Sensor (Including CTP Switch)
5. Vehicle Speed Sensor (VSS)
6. Intake Air Temperature (IAT) Sensor
7. Mass Air Flow (MAF) Sensor
8. Camshaft Position (CMP) Sensor
9. Crankshaft Position (CKP) Sensor
10. Knock Sensor (KS) System
11. Evaporative Emission (EVAP) Control System
12. Idle Air Control (IAC) System
13. CMP Actuator Solenoid System
14. Rocker Arm Oil Control system
15. Misfire Detection
16. Fuel-Trim
17. Catalyst Monitor
18. Central Processing Unit (CPU) Of The PCM

When PCM detects a malfunction in one of the above areas, PCM will illuminate or flash the MIL to notify driver of the occurrence of a fault. PCM will store a DTC when PCM illuminates the MIL. PCM will turn OFF the MIL after 3 consecutive ignition cycles without the malfunction occurring. DTC will remain stored in the PCM memory after the MIL is OFF.

SCAN TOOL DATA LIST

Note. A scan tool that displays faulty data should not be used. The scan tool problem should be reported to the manufacturer. The use of a faulty scan tool can result in misdiagnosis and unnecessary parts replacement.

The Engine Scan Tool Data List contains all engine related parameters that are available on the scan tool. The list is arranged in alphabetical order. See appropriate PID VALUE CHARTS article. Use the Engine Scan Tool Data List only after verifying the following

1. The Diagnostic System Check - Engine Controls is completed.
2. No Diagnostic Trouble Codes (DTC) are present.
3. The on-board diagnostics are functioning properly.

Scan tool values from a properly running engine may be used for comparison with the engine you are diagnosing. The engine scan tool data list represents values that would be seen on a normally running engine.

If all values are within the typical range described, diagnose by symptom. See TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.

SCAN TOOL OUTPUT CONTROLS - ENGINE CONTROLS

SCAN TOOL OUTPUT CONTROLS

DIAGNOSTIC STARTING POINT - ENGINE CONTROLS

Begin the system diagnosis with Diagnostic System Check - Engine Controls. The Diagnostic System Check - Engine Controls will provide the following information

1. The identification of control modules which command the system.
2. The ability of control modules to communicate through serial data circuit.
3. The identification of any stored Diagnostic Trouble Codes (DTCs) and the codes statuses.

The use of the Diagnostic System Check - Engine Controls will identify the correct procedure for diagnosing the system and where the procedure is located. See

DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS

DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS

Note. Check for applicable Technical Service Bulletins (TSB) before proceeding. DO NOT perform the following procedure if driveability conditions are not present unless directed from another procedure. DO NOT clear DTCs unless instructed by a diagnostic procedure. If there is a condition with the starting system, refer to appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. Ensure battery is fully charged. Ensure battery cables are clean and tight. Ensure Powertrain Control Module (PCM) grounds are clean, tight, and in the proper location.

Diagnostic Procedures

1. Connect scan tool. Does scan tool power-up? If yes, go to next step. If no, perform SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
2. Turn ignition switch to RUN position, engine OFF. Attempt to establish communication with Powertrain Control Module (PCM). Does the scan tool communicate with PCM? If yes, go to next step. If no, go to SCAN TOOL DOES NOT COMMUNICATE WITH PCM in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
3. Attempt to start engine. Does engine start and idle? If yes, go to next step. If no, go to «ENGINE CRANKS BUT DOES NOT RUN»(ref-152426-S24080731382003032400000) under NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 1.8L VIBE article.
4. Select the DTC display function for the PCM. Does scan tool display any powertrain DTCs? If yes, go to next step. If no, go to step 7 .
5. Using scan tool, save or capture the powertrain DTC information and store information. When complete, go to next step.
6. Does scan tool display DTC P1600? If yes, go to «P0601-P0607, P1600, P1621, P1627, P1680, P1681, P1683 Or P2610: ECU MALFUNCTION»(ref-152429-S07892531672003020400000) under DIAGNOSTIC TESTS. If no, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) .
7. Is customer's concern related to the automatic transmission? If yes, diagnose transmission problems. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If no, go to next step.
8. Is customer's concern with Inspection/Maintenance (I/M) testing? If yes, see «INSPECTION/MAINTENANCE SYSTEM CHECK»(ref-152429-S16683892272003020400000) under DRIVE CYCLES. If no, go to next step.
9. Check for the following symptoms: Hard start. Surges/chuggles. Lack of power, Sluggishness/sponginess. Detonation/spark knock. Hesitation, sag, stumble. Cuts out, misses. Poor fuel economy. Poor fuel fill quality. Rough idle, unstable idle, incorrect idle and stalling. Dieseling, run-on. Backfire. MIL inoperative. MIL always on. Did you find and correct the condition? If yes, system is okay. If no, problem is intermittent. See «INTERMITTENTS»(ref-153013-S39990244982003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.

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). (Scheme 4) The DLC is located under the instrument panel to the left of the steering column. The DLC is used to connect to a scan tool. Some common uses of the scan tool are identifying stored DTCs, clearing the DTCs, performing output control tests and reading the serial data. Follow the instructions supplied by the scan tool manufacturer to read DTCs accurately. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS.

Scheme 4

CLEARING DIAGNOSTIC TROUBLE CODES

Note. Do not clear the DTCs unless directed to do so by the service information provided for each diagnostic procedure. The Freeze Frame data which may help diagnose an intermittent fault will be erased from the memory when the DTCs are cleared.

The PCM will begin to count the warm-up cycles when the fault that caused the DTC to be stored into memory has been corrected. The DTC will automatically be cleared from the PCM memory when the PCM has counted 40 consecutive warm-up cycles with no further faults detected.

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. To clear DTCs, use the scan tools CLEAR DTC Information function. Follow the instructions supplied by the scan tool manufacturer.

Conditions for Clearing MIL/DTC - Type "A" or Type "B"

1. The control module turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC Last Test Failed clears when the diagnostic runs and passes.
3. Use a scan tool to clear the MIL and the DTC.

Conditions for Clearing DTC - Type "C"

1. A last test failed, or current DTC, clears when the diagnostic runs and passes.
2. Use a scan tool to clear the DTC.

SCAN TOOL USAGE

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

Scan tool 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. Many DTC related repairs will instruct the technician to clear DTC information. This procedure will reset ALL I/M System Status indicators to NO, and require performing the I/M Complete System Set Procedure.

1. Perform powertrain diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM. Repair any DTCs or driveability concerns that would prevent I/M System Status tests from completing. Did you find and repair a DTC or driveability concern? If yes, go to step 3 . If no, go to next step.
2. Review any service bulletins for software updates that may prevent I/M readiness. Perform any reprogramming or repairs indicated by the service bulletins. Was a repair service required? If yes, see «INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE»(ref-152429-S37971947542003020400000) . If no, go next step.
3. Using scan tool, observe I/M SYSTEM STATUS display. Is more than one test indicating a NO status? If yes, see «INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE»(ref-152429-S37971947542003020400000) . If no, go to appropriate INSPECTION/MAINTENANCE SYSTEM SET procedure for the indicated system.

Diagnostic Aids

I/M SYSTEM STATUS display provides an indication of when the control module has completed the required tests. This does not necessarily mean the test has passed, only that a decision was made. If the diagnostic fails, a DTC will indicate the failure. If a failure indication is present for a DTC associated with one of the I/M regulated systems, it may prevent other required tests from running. For example, a DTC for the control circuit of the relay controlling an AIR pump may not be listed in the Inspection/Maintenance System DTCs because it is a continuous test. If this DTC is set, the ACTIVE TESTS for the AIR system may not run.

The I/M System Status information may be useful for a technician to determine if diagnostics have run when verifying repairs.

Conditions For Running

Ensure vehicle meets the following conditions before performing procedure

1. Barometric pressure is greater than 22 in. Hg (75 kPa).
2. Engine coolant temperature is less than 75°F (24°C).
3. Battery voltage is 10.5-18 volts.
4. Fuel level is 25-75 percent.

1. Did you perform the Inspection/Maintenance (I/M) system check? If yes, go to next step. If no, see «INSPECTION/MAINTENANCE SYSTEM CHECK»(ref-152429-S16683892272003020400000) .
2. Ensure that the vehicle is within the Conditions for Running. See «CONDITIONS FOR RUNNING»(ref-152429-S00502122242003020400000) . Turn OFF all accessories, e.g., A/C, blower fan, etc. Set vehicle parking brake. Verify transmission is in Park (A/T) or Neutral (M/T). Start engine and allow engine to idle. Idle engine until an operating temperature of at least 158°F (70°C) is reached. This may be up to 8-10 minutes depending on the start up coolant temperature. Once the engine is started, DO NOT turn OFF the engine for the remainder of the procedure until the test is complete. When complete, go to next step.
3. For the next group of tests to run, vehicle must operate in the following conditions: Acceleration at part throttle to 45-55 MPH (56-90 km/h). Speed maintained for 4 minutes or until I/M System Status indicator updates to YES. When complete, go to next step.
4. Important: For this test to run, the vehicle must operate in the following conditions: Deceleration to zero MPH. Engine idling for 2 minutes while service brake depressed, automatic transmission in Drive and manual transmission in Neutral with clutch pedal depressed. When complete, go to next step.
5. For the next group of tests to run, vehicle must operate in the following conditions: Acceleration at part throttle to 45-55 MPH (56-90 km/h). Speed maintained for 4 minutes or until I/M System Status indicator updates to YES. When complete, go to next step.
6. With a scan tool, observe I/M SYSTEM STATUS display. Did all of I/M system status indicators update to YES? If yes, go to next step. If no, go to I/M SYSTEM SET procedure for the indicated systems.
7. Using scan tool, observe emission related DTC portion of I/M SYSTEM STATUS display. Does the scan tool indicate any emission related DTCs set? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

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

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

1. Barometric pressure is greater than 75 kPa.
2. Engine coolant temperature is 158°F (70°C).
3. Battery voltage is 10.5-16.0 volts.

1. Did you perform the Inspection/Maintenance (I/M) system check? If yes, go to next step. If no, go to «INSPECTION/MAINTENANCE SYSTEM CHECK»(ref-152429-S16683892272003020400000) .
2. Ensure vehicle is within conditions for running. See «CONDITIONS FOR RUNNING»(ref-152429-S34499496422003020400000) . Turn OFF all accessories, e.g., A/C, blower fan, etc. Start and idle the engine. Important: For this test to run, vehicle must operate in the following conditions: Idle engine for one minute after reaching operating temperature of 158°F (70°C). Acceleration at part throttle to 35-55 MPH (56-90 km/h) with this speed maintained for 2-3 minutes or until I/M system status updates to YES. Using scan tool, observe I/M system status display. Did the catalyst system status update to YES? If yes, go to step 5 . If no, go to next step.
3. Using scan tool, observe DTC information. Does scan tool indicate any failed DTCs? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, go to next step.
4. Operate vehicle within Conditions for Running the DTC. See «CONDITIONS FOR RUNNING»(ref-152429-S34499496422003020400000) . Repeat procedure until scan tool indicates the diagnostic test has run. Using scan tool, observe I/M System Status display. Did the Catalyst System Status update to YES? If yes, go next step. If no, see «DIAGNOSTIC AIDS»(ref-152429-S37567827172003020400000) .
5. Using scan tool, observe emission related DTC portion of I/M system status display. Does scan tool indicate any emission related DTCs? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

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

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

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

I/M system status will update only when an emission related DTC fails the second time, or when all tests pass.

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

If a diagnostic test is difficult to run, maintain necessary enable conditions until system status updates to YES.

Note. This is for non scan tool Service Bay Test equipped vehicles.

1. Barometric pressure is greater than 75 kPa.
2. Engine coolant temperature is less than 158°F (70°C) after engine warm-up.
3. Fuel level is 25-75 percent.
4. Battery voltage is 10.5-16.0 volts.
5. Vehicle has been driven for at least 20 minutes.
6. Test will initiate only after a cold start. Engine coolant temperature is 50-95°F (10-35°C) and ECT and Intake Air Temperature (IAT) are near the same temperature.

1. Did you perform the Inspection/Maintenance (I/M) system check? If yes, go to next step. If no, go to «INSPECTION/MAINTENANCE SYSTEM CHECK»(ref-152429-S16683892272003020400000) .
2. Ensure vehicle is within «CONDITIONS FOR RUNNING»(ref-152429-S22211826922003020400000) . Turn OFF all accessories, e.g., A/C, blower fan, etc. Start and idle engine. Idle engine until engine reaches operating temperature of at least 70°C (158°F). This may be up to 8-10 minutes depending on start up coolant temperature. Acceleration at part throttle to 30-50 MPH (48-80 km/h) and cruise for 3 minutes after engine reaches operating temperature. Deceleration to zero MPH. Engine idling for one minute while the following criteria is maintained: Service brake depressed. Automatic transmission in Drive. Manual transmission in Neutral with clutch pedal depressed. Accelerate at part throttle to 40-45 MPH (64-72 km/h) and maintain this speed for one minute. Using scan tool, observe I/M SYSTEM STATUS display. Did EVAP system status update to YES? If yes, go to step 5 . If no, go to next step.
3. Using scan tool, observe DTC Information. Does scan tool indicate any failed DTCs? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, go to next step.
4. See «INSPECTION/MAINTENANCE SYSTEM DTCS»(ref-152429-S33380700592003020400000) to determine which DTCs are required to run to complete this test. Operate vehicle within conditions for running DTC. See «CONDITIONS FOR RUNNING»(ref-152429-S22211826922003020400000) . Repeat procedure until scan tool indicates the diagnostic test has run. Using scan tool, observe I/M SYSTEM STATUS display. Did EVAP system status update to YES? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(ref-152429-S35592656262003020400000) .
5. Using scan tool, observe EMISSION RELATED DTC portion of I/M SYSTEM STATUS display. Does scan tool indicate any emission related DTCs set? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

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

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

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

The I/M system status will update only when an emission related DTC fails the second time, or when all tests pass.

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

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

1. Engine coolant temperature is more than 158°F (70°C).
2. Engine operating in closed-loop.
3. Battery voltage is 10.5-16.0 volts.

1. Did you perform the Inspection/Maintenance (I/M) system check? If yes, go to next step. If no, go to «INSPECTION/MAINTENANCE SYSTEM CHECK»(ref-152429-S16683892272003020400000) .
2. Ensure vehicle is within conditions for running. See «CONDITIONS FOR RUNNING»(ref-152429-S24203190532003020400000) . Turn OFF all accessories, e.g., A/C, blower fan, etc. Start and idle engine. For this test to run, vehicle must operate in the following conditions: Accelerate engine to 30-50 MPH (48-80 km/h) and cruise for 3 minutes after engine reaches operating temperature. Deceleration to zero MPH. Idle engine for 2 minutes While the following criteria is maintained: Service brake is depressed. Automatic transmission in Drive. Manual transmission in Neutral with the clutch pedal depressed. Accelerate at part throttle to 30-50 MPH (48-80 km/h) with this speed maintained for 30 seconds. Using scan tool, review I/M SYSTEM STATUS display. Did HO2S/O2S system status update to YES? If yes, go to step 5 . If no, go to next step.
3. Using scan tool, observe DTC Information. If scan tool indicates any failed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If scan tool does not indicate any failed DTCs, go to next step.
4. Operate vehicle within conditions for running DTC. See «CONDITIONS FOR RUNNING»(ref-152429-S24203190532003020400000) . Repeat procedure until scan tool indicates the diagnostic test has run. With a scan tool, observe I/M SYSTEM STATUS display. Did HO2S/O2S system status update to YES? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(ref-152429-S38368729592003020400000) .
5. Using scan tool, observe emission related DTC portion of the I/M system status display. Does scan tool indicate any emission related DTCs set? If yes, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

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

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

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

I/M system status will update only when an emission related DTC fails the second time, or when all tests pass.

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

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

1. Engine is running.
2. Battery voltage is 10.5-16.0 volts.
3. Intake Air Temperature (IAT) is less than 90°F (32°C).
4. Test will always initiate after a cold start. The control module considers the engine to be cold if engine coolant temperature is below 75°F (24°C).

1. Did you perform the Inspection/Maintenance (I/M) system check? If yes, go to next step. If no, go to «INSPECTION/MAINTENANCE SYSTEM CHECK»(ref-152429-S16683892272003020400000) .
2. Start and idle engine. Ensure vehicle is within conditions for running specified in supporting text. See «CONDITIONS FOR RUNNING»(ref-152429-S14837094872003020400000) . Set vehicle parking brake. Verify transmission is in Park for automatic transmissions and Neutral for manual transmissions. Turn OFF all accessories, e.g., A/C, blower fan, etc. Start engine and let idle. Idle engine until engine reaches operating temperature of at least 158°F (70°C). This may be up to 8-10 minutes depending on start up coolant temperature. For the remaining portion of this test to run, vehicle must operate in the following conditions: Acceleration at part throttle to 30-50 MPH (48-80 km/h). Speed maintained for 2 minutes or until I/M system status indicator updates to YES. Did the HO2S heater system status update to YES? If yes, go to step 5 . If no, go to next step.
3. Using scan tool, observe DTC information. Does scan tool indicate any failed DTCs? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, go next step. NOTE: Refer to «INSPECTION/MAINTENANCE SYSTEM DTCS»(ref-152429-S33380700592003020400000) to determine which DTCs are required to run to complete this test.
4. Refer to «INSPECTION/MAINTENANCE SYSTEM DTCS»(ref-152429-S33380700592003020400000) to determine which DTCs are required to run to complete this test. Operate vehicle within conditions for running DTC. See «CONDITIONS FOR RUNNING»(ref-152429-S14837094872003020400000) . Repeat procedure until scan tool indicates diagnostic test has run. With a scan tool, observe I/M SYSTEM STATUS display. Did HO2S heater system status update to YES? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(ref-152429-S38368729592003020400000) .
5. Using scan tool, observe emission related DTC portion of I/M system status display. Does scan tool indicate any emission related DTCs set? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

HO2S heater tests will normally run within 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 the 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 from initiating. Oxygen sensor heaters are operated by the engine control module. The control module has the ability to monitor current required by the heaters and does this on a continuous basis.

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

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

I/M system status will update only when an emission related DTC fails the second time, or when all tests pass.

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

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

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).

DIAGNOSTIC TROUBLE CODE DEFINITIONS

Scheme 5

Scheme 6

Scheme 7

Scheme 8

Scheme 9

Scheme 10

Scheme 11

Scheme 12

Scheme 13

Scheme 14

Scheme 15

Scheme 16

Scheme 17

Scheme 18

Scheme 19

Scheme 20

Scheme 21

Scheme 22

Scheme 23

Scheme 24

Scheme 25

Scheme 26

Scheme 27

Scheme 28

Scheme 29

Scheme 30

Scheme 31

Scheme 32

Scheme 33

Scheme 34

Scheme 35

Scheme 36

Scheme 37

Scheme 38

Scheme 39

Scheme 40

Scheme 41

Scheme 42

Scheme 43

Scheme 44

Scheme 45

Scheme 46

Scheme 47

Scheme 48

Scheme 49

Scheme 50

Scheme 51

Scheme 52

Scheme 53

Scheme 54

Scheme 55

Circuit Description

There should always be a steady Malfunction Indicator Light (MIL) when ignition switch is in RUN position, engine not running. System voltage is applied to the indicator bulb and Powertrain Control Module (PCM) provides a path to ground. Once engine starts, PCM turns the MIL OFF. When an engine control system malfunction occurs, PCM turns ON the MIL and a diagnostic trouble code is stored in memory.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) .
2. Connect scan tool. Turn ignition switch to RUN position, engine OFF. Does scan tool display any engine data? If yes, go to next step. If no, go to SCAN TOOL DOES NOT COMMUNICATE WITH PCM in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
3. Observe Instrument Panel Cluster (IPC) assembly operation. Do all other IPC functions operate normally? If yes, go to next step. If no, go to appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT.
4. Turn ignition switch to OFF position. Disconnect PCM White 34-pin harness connector (with MIL control circuit). Turn ignition switch to RUN position, engine OFF. Probe MIL control circuit on harness side using a 3-amp fuse jumper wire to ground. Does MIL illuminate? If yes, go to step 9 . If no, go to next step.
5. Did the fuse in the jumper wire open? If yes, go to next step. If no, go to step 7 .
6. Repair short to voltage in MIL control circuit. After repair, go to step 10 .
7. Backprobe MIL control circuit at IPC assembly with a 3-amp fuse jumper wire to ground. Does the MIL illuminate? If yes, go to next step. If no, go to appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT.
8. Repair open in the MIL control circuit. After repair, go to step 10 .
9. Replace PCM. After repair, go to next step.
10. Turn ignition switch to RUN position, engine OFF. Is MIL illuminated? If yes, go to next step. If no, go to next step 2 .
11. Use scan tool to clear DTCs. Turn ignition OFF for 30 seconds. Start engine. Observe MIL operation. Is MIL illuminated? If yes, go to «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM. If no, system is okay at this time.

An intermittent malfunction may be caused by a faulty electrical connection in MIL circuit. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.

There should be a steady Malfunction Indicator Light (MIL) when ignition switch is in RUN position, prior to starting the engine. Battery ignition voltage is supplied to MIL. Powertrain Control Module (PCM) will illuminate MIL by grounding the control circuit at the PCM. A steady MIL with the engine running suggests a short to ground in the MIL control circuit, or a Diagnostic Trouble Code (DTC) is stored.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition switch to OFF position. Disconnect PCM White 34-pin harness connector (with MIL control circuit). Turn ignition switch to RUN position, engine OFF. Is MIL illuminated? If yes, go to next step. If yes, go to step 4 .
3. Repair short to ground in MIL control circuit between PCM and IPC assembly. After repair, go to step 5 .
4. Replace PCM. After repair, go to next step.
5. Start engine and observe the MIL. Does MIL turn OFF approximately 1 to 2 seconds after engine is started? If yes, go to next step. If no, go to step 2 .
6. Using scan tool, the stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Check for the following conditions

1. Check for a shorted MIL control circuit between PCM and IPC assembly.
2. A shorted IPC assembly board may cause MIL to stay illuminated.

An intermittent malfunction may be caused by a faulty electrical connection. See

INTERMITTENTS

in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.

DIAGNOSTIC TESTS

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

Conditions For Running DTC

Ignition switch is in RUN position or engine is running.

Conditions For Setting DTC

1. An open or a short is detected in MAF sensor signal circuit when engine speed is less than 4000 RPM.
2. Condition is present for at least 3 seconds.

Or

1. An open or a short is detected in MAF sensor signal circuit when engine speed is at least 3000 RPM.
2. Condition is present for at least 3 seconds.
3. Condition is present on 2 consecutive ignition cycles.

Action Taken When DTC Sets

1. PCM illuminates Malfunction Indicator Light (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with fault active.
2. PCM records operating conditions at the time the diagnostic fails. This information will be stored in the freeze frame buffer.
3. PCM enters FAIL-SAFE FUNCTION and operates with ignition timing fixed at 5 degrees Before Top Dead Center (BTDC).

Conditions For Clearing MIL/DTC

1. MIL turns OFF after 3 consecutively passing cycles without a fault present.
2. A History DTC will clear after 40 consecutive warm-up cycles without a fault.
3. Perform scan tool CLEAR DTC INFORMATION function to clear DTC.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Select MAF sensor parameter on scan tool. Is MAF sensor value more than or equal to 185.0 g/s? If yes, go to step 7 . If no, go to next step.
3. Observe MAF sensor parameters on scan tool. Is MAF sensor less than or equal to 0.45 g/s? If yes, go to step 5 . If no, go to next step.
4. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions specified. Does a DTC P0100 set? If yes, go to step 2 . If no, see «INTERMITTENTS»(ref-153013-S39990244982003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.
5. Turn ignition OFF. Disconnect MAF sensor 5-pin harness connector. Turn ignition switch to RUN position, engine OFF. Using a test light connected to ground, probe ignition positive voltage circuit. Is the test light illuminated? If yes, go to next step. If no, go to step 10 .
6. Turn ignition OFF. Connect MAF sensor 5-pin harness connector. Turn ignition switch to RUN position, engine OFF. Backprobe MAF signal high circuit at the PCM with a DMM connected to ground. Is MAF signal high voltage 0.5-3.0 volts? If yes, go to step 11 . If no, go to step 12 .
7. Turn ignition OFF. Disconnect MAF sensor 5-pin harness connector. Turn ignition switch to RUN position, engine OFF. Connect a test light between battery voltage and MAF signal low circuit. Does the test light illuminate? If yes, go to next step. If no, go to step 9 .
8. Measure MAF signal high circuit voltage at MAF sensor harness connector using a DMM connected to ground. Is MAF signal high circuit voltage more than 0.2 volt? If yes, go to step 13 . If no, go to step 15 .
9. Check for an open in MAF sensor signal low circuit. Repair as necessary. Did you find and correct a condition? If yes, go to step 18 . If no, go to step 14 .
10. Repair open in MAF sensor ignition positive voltage circuit. After you complete the repair, go to step 18 .
11. Remove MAF sensor from air cleaner housing. Continue to backprobe MAF signal high circuit at PCM using DMM. Observe voltage on MAF signal high circuit while blowing gently into MAF sensor orifice. Did the signal high circuit voltage increase when blowing air into the sensor orifice? If yes, go to step 14 . If no, go to step 15 .
12. Check for an open or a short to ground in MAF signal high circuit. Repair as necessary. Did you find and correct a condition? If yes, go to step 18 . If no, go to step 17 .
13. Check for a short to voltage in MAF signal high circuit. Repair as necessary. Did you find and correct a condition? If yes, go to step 18 . If no, go to step 17 .
14. Check for an intermittent or a poor electrical connection at PCM. Repair as necessary. Did you find and correct a condition? If yes, go to step 18 . If no, go to step 17 .
15. Check for an intermittent or a poor electrical connection at MAF sensor. Repair as necessary. Did you find and correct a condition? If yes, go to step 18 . If no, go to next step.
16. Replace MAF sensor. After repair, go to step 18 .
17. Replace PCM. After repair, go to step 18 .
18. Use scan tool to clear DTCs. Turn ignition OFF for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING THE DTC»(ref-152429-S37849176192003020400000) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
19. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that you have not diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

1. Engine is running.
2. ECT is at least 158°F (70°C).

1. Engine speed is 900 RPM or less.
2. Throttle valve is closed.
3. MAF sensor output is more than 2.2 volts.
4. Condition is present for at least 10 seconds.

Or

1. TP sensor input is at least 0.1 volt.
2. MAF sensor output is less than 1.0 volt.
3. Condition is present for at least 6 seconds.

1. PCM illuminates the Malfunction Indicator Light (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with fault active.
2. PCM records operating conditions at the time the diagnostic fails. Information will be stored in the freeze frame buffer.

1. MIL turns OFF after 3 consecutively passing cycles without a fault present.
2. A History DTC will clear after 40 consecutive warm-up cycles without a fault.
3. Perform scan tool CLEAR DTC INFORMATION function.

1. Perform diagnostic system check - engine controls. If yes, go to next step. If no, go to «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Check for any other DTCs. Repair any other DTCs first. Are there any other DTCs set? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, go to next step.
3. Check for any of the following conditions: Any objects blocking MAF sensor inlet. Any intake manifold vacuum leaks. Any throttle body vacuum leaks. A faulty, missing, or incorrectly installed PCV valve. Repair as necessary. Was a repair necessary? If yes, go to step 7 . If no, go to next step.
4. Turn ignition switch to RUN position, engine OFF. Using scan tool, place control module into CHECK MODE. See «SERVICE BAY TESTS»(ref-152429-S19809249722003021000000) under SELF-DIAGNOSTIC SYSTEM. Operate vehicle within freeze frame conditions. Is DTC P0101 set? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(ref-152429-S06247686142003020400000) .
5. Check for the following conditions: Check for poor connections in MAF sensor circuits. Check for high resistance in MAF sensor electrical circuits. Check for at least 11 volts on ignition positive voltage circuit. Repair as necessary. Was a repair necessary? If yes, go to step 7 . If no, go to next step.
6. Replace MAF sensor. After repair, go to next step.
7. Use scan tool to clear DTCs. Turn ignition OFF for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S03480060742003020400000) . Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
8. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that you have not diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Check for any of the following conditions

1. Excessive deposits on throttle plate or throttle bore.
2. A sticking or binding throttle plate.
3. A misrouted wiring harness. Check MAF sensor harness to ensure harness is not routed too close to high voltage wires such as spark plug leads.
4. A damaged wiring harness. Check wiring harness for damage. If harness appears to be okay, observe scan tool while moving connectors and wiring harnesses related to MAF sensor. A change in the display will indicate location of the fault.
5. Observe Heated Oxygen (HO2S) voltage and fuel trim readings using a scan tool. If HO2S voltage is fixed low, while fuel trim is constantly high, check MAF sensor signal circuit for resistance. High circuit resistance can cause the sensor to read a lower volume of air than actual, resulting in a lean fueling condition.
6. A plugged intake air duct or a dirty air filter element. A Wide Open Throttle (WOT) acceleration from a stop should cause MAF parameter displayed on a scan tool to increase from about 2-3.5 g/s at idle to about 90-100 g/s or more at the time of the 1-2 shift. If detected airflow is significantly smaller, check for a restriction or blockage in the intake air system.

An intermittent malfunction may be caused by a fault in MAF sensor circuit. Check wiring harness and components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.

If DTC P0101 cannot be duplicated, information included in freeze frame data can be useful in determining vehicle operating conditions when the DTC was first set.

Ignition switch is in RUN position.

Temperature input is -40°F (-40°C) for at least 0.5 second or temperature input is 284°F (140°C) for at least 0.5 second.

1. PCM illuminates the Malfunction Indicator Light (MIL).
2. PCM records operating conditions at the time the diagnostic fails. This information is stored in freeze frame buffer.
3. PCM enters FAIL SAFE FUNCTION in which intake air temperature will default to 68°F (20°C).

1. MIL turns OFF after 3 consecutively passing trips without a fault present.
2. A History DTC clears after 40 consecutive warm-up cycles without a fault.
3. Use scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Select IAT sensor parameter on the scan tool. Is IAT sensor value more than or equal to 284°F (140°C)? If yes, go to step 5 . If no, go to next step.
3. Select IAT sensor parameter on scan tool. Is IAT sensor value less than or at -40°F (-40°C)? If yes, go to step 7 . If no, go to next step.
4. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within freeze frame conditions as specified. Does DTC P0110 set? If yes, go to step 2 . If no, go to «DIAGNOSTIC AIDS»(ref-152429-S20017747562003020400000) .
5. Turn ignition switch to RUN position, engine OFF. Disconnect MAF sensor 5-pin harness connector. Observe MAF sensor parameter on the scan tool. Is IAT sensor value equal to -40°F (-40°C)? If yes, go to step 13 . If no, go to next step.
6. Turn ignition switch to OFF position. Check IAT sensor input circuit for a short to ground. Ensure input circuit is not shorted to the sensor ground circuit. Repair as necessary. Is the action complete? If yes, go to step 15 . If no, go to step 14 .
7. Disconnect MAF sensor 5-pin harness connector. Jump IAT input circuit and sensor ground circuit together at IAT sensor harness connector. Observe IAT sensor parameter on scan tool. Is IAT sensor value more than or equal to 284°F (140°C)? If yes, go to step 9 . If no, go to next step.
8. Jump IAT sensor input circuit to ground at MAF sensor harness connector. Observe IAT sensor parameter on scan tool. Is IAT sensor value more than or equal to 284°F (140°C)? If yes, go to step 10 . If no, go to step 11 .
9. Check for faulty electrical connections at MAF sensor. Repair as necessary. Was a repair necessary? If yes, go to step 15 . If no, go to step 12 .
10. Turn ignition OFF. Check IAT sensor ground circuit for an open. Repair as necessary. Was a repair necessary? If yes, go to step 15 . If no, go to step 12 .
11. Turn ignition OFF. Check IAT sensor input circuit for an open or a short. Repair as necessary. Was a repair necessary? If yes, go to step 15 . If no, go to next step.
12. Check for faulty IAT circuit terminal connections at PCM. Repair as necessary. Was a repair necessary? If yes, go to step 15 . If no, go to step 14 .
13. Replace MAF sensor. After repair, go to step 15 .
14. Replace PCM. After repair, go to step 15 .
15. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S42411307842003020400000) . Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
16. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Use the Temperature vs. Resistance table to evaluate the possibility of a shifted IAT sensor. See TEMPERATURE VS. RESISTANCE table. A shifted sensor could result in a DTC P0110.

An intermittent malfunction may be caused by a fault in IAT sensor electrical circuit. Check wiring harness and components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. If a DTC P0110 cannot be duplicated, information included in freeze frame data can be useful in determining vehicle operating conditions when DTC was first set.

TEMPERATURE VS. RESISTANCE

1. Engine is running.

Temperature input is -40°F (-40°C) for at least 0.5 second or temperature input is 284°F (140°C) for at least 0.5 second.

1. PCM illuminates Malfunction Indicator Light (MIL).
2. PCM records operating conditions at the time the diagnostic fails. This information is stored in freeze frame buffer.
3. PCM enters FAIL SAFE FUNCTION in which coolant temperature will default to 176°F (80°C).

1. MIL turns OFF after 3 consecutively passing trips without a fault present.
2. A History DTC clears after 40 consecutive warm-up cycles without a fault.
3. Use scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Select ECT sensor parameter on scan tool. Is ECT sensor value more than or equal to 284°F (140°C)? If yes, go to step 5 . If no, go to next step.
3. Select ECT sensor parameter on scan tool. Is ECT sensor value less than or equal to -40°F (-40°C)? If yes, go to step 7 . If no, go to next step.
4. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S06968009492003020400000) . Does the DTC run and pass? If yes, go to step 2 . If no, go to «DIAGNOSTIC AIDS»(ref-152429-S19712527202003020400000) .
5. Turn ignition switch to RUN position, engine OFF. Disconnect ECT sensor 2-pin harness connector. Select ECT sensor parameter on the scan tool. Is ECT sensor value equal to -40°F (-40°C)? If yes, go to step 13 . If no, go to next step.
6. Turn ignition OFF. Disconnect PCM White 34-pin harness connector. Check ECT sensor input circuit for a short to ground. Ensure input circuit is not shorted to the sensor ground circuit. Repair as necessary. Was a repair necessary? If yes, go to step 15 . If no, go to step 14 .
7. Disconnect ECT sensor 2-pin harness connector. Jump ECT input circuit and sensor ground circuit together at ECT sensor harness connector. Select ECT sensor parameter on scan tool. Is ECT sensor value more than or equal to 284°F (140°C)? If yes, go to step 10 . If no, go to step 11 .
8. Jump the ECT input circuit at ECT sensor harness connector to chassis ground. Select ECT sensor parameter on scan tool. Is ECT sensor value more than or equal to 284°F (140°C)? If yes, go to step 10 . If no, go to step 11 .
9. Check for faulty electrical connections at ECT sensor. Repair as necessary. Was a repair necessary? If yes, go to step 15 . If no, go to step 13 .
10. Turn ignition OFF. Disconnect PCM White 34-pin harness connector. Check ECT sensor ground circuit for an open. Repair as necessary. Was a repair necessary? If yes, go to step 15 . If no, go to step 12 .
11. Turn ignition OFF. Disconnect PCM 34-pin harness connector. Check ECT sensor input circuit for an open. Repair as necessary. Was a repair necessary? If yes, go to step 15 . If no, go to step 12 .
12. Check for a faulty ECT circuit terminal connection at PCM. Repair as necessary. Was a repair necessary? If yes, go to step 15 . If no, go to step 14 .
13. Replace ECT sensor. After repair, go to step 15 .
14. Replace PCM. After repair, go to step 15 .
15. Using scan tool, clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S06968009492003020400000) . Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
16. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

1. If DTCs P0105, P0110, P0115, and P0120 are also set, malfunction may be a faulty sensor ground circuit.
2. Check for a faulty electrical connection to PCM.
3. Check for proper operation of the engine cooling system and verify correct coolant level.
4. Use the Temperature vs. Resistance table to evaluate possibility of a shifted ECT sensor. A shifted sensor could result in a DTC P0115. See «TEMPERATURE VS. RESISTANCE»(ref-152429-S40771357512003021200000) table.

An intermittent malfunction may be caused by a fault in ECT sensor electrical circuit. Check wiring harness and components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Repair any electrical circuit faults found.

If DTC P0115 cannot be duplicated, information included in freeze frame data can be useful in determining vehicle operating conditions when DTC first set.

Note. No conditions were specified by manufacturer.

1. Engine coolant temperature is less than 20°F (-7°C) at engine start up.
2. ECT sensor value is 68°F (20°C) or less after engine has been running for 20 minutes or more.

Or

1. Engine coolant temperature is 20-50°F (-7 to 10°C) at engine start up.
2. ECT sensor value is 68°F (20°C) or less after engine has been running for 5 minutes or more.

1. PCM illuminates the Malfunction Indicator Light (MIL) after 2 consecutive ignition cycles in which diagnostic runs with fault active.
2. PCM records operating conditions at the time the diagnostic fails. This information is stored in freeze frame buffer.

1. Malfunction Indicator Light (MIL) turns OFF after 3 consecutively passing trips without a fault present.
2. A History DTC clears after 40 consecutive warm-up cycles without a fault.
3. Clear MIL and DTC with a scan tool.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Check for DTC P0115 with a scan tool. Is DTC P0115 set? If yes, go to «DTC P0115: ECT SENSOR CIRCUIT»(ref-152429-S24935653322003020400000) . If no, go to next step.
3. Measure actual coolant temperature. Turn ignition switch to RUN position, engine OFF. Observe ECT sensor parameter on scan tool. Is ECT sensor value displayed near actual coolant temperature? If yes, go to step 11 . If no, go to next step.
4. Turn ignition OFF. Disconnect ECT sensor harness connector. Observe ECT sensor parameter on scan tool. Does engine coolant temperature equal -40°F (-40°C)? If yes, go to next step. If no, go to step 8 .
5. Disconnect ECT sensor 2-pin harness connector. Jump ECT sensor input circuit and ground circuit together at ECT sensor harness connector. Observe ECT sensor parameter on scan tool. Does engine coolant temperature equal 284°F (140°C)? If yes, go to step 13 . If no, go to next step.
6. Jump ECT sensor input circuit to chassis ground. Observe ECT sensor parameter on scan tool. Does engine coolant temperature equal 284°F (140°C)? If yes, go to next step. If no, go to step 8 .
7. Repair open or high resistance in ECT sensor ground circuit. Is the action complete? If yes, go to step 14 . If no, go to step 9 .
8. Turn ignition OFF. Disconnect PCM White 34-pin harness connector C1. Check ECT sensor input circuit for a short or a high electrical resistance. Repair as necessary. Was a repair necessary? If yes, go to step 14 . If no, go to next step.
9. Check for a faulty connection at PCM and ECT harness connectors. Repair as necessary. Was a repair necessary? If yes, go to step 14 . If no, go to next step.
10. Replace PCM. After repair, go to step 14 .
11. Check engine cooling system for any of the following conditions: A faulty thermostat. A low engine coolant level. The correct coolant solution. Any faulty cooling system operation. Repair as necessary. See appropriate SPECIFICATIONS & DRIVE BELT ROUTING article under COOLING SYSTEM (MECHANICAL). Was a repair necessary? If yes, go to step 14 . If no, go to next step.
12. Use scan tool to clear DTCs. Place vehicle into CHECK MODE, using scan tool. See «SERVICE BAY TESTS»(ref-152429-S19809249722003021000000) under SELF-DIAGNOSTIC SYSTEM. Operate vehicle within freeze frame conditions as specified. Does DTC P0116 set? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(ref-152429-S24282279642003020400000) .
13. Replace ECT sensor. After repair, go to next step.
14. Use scan tool to clear DTCs and road test vehicle within freeze frame conditions that set the DTC. Review scan tool data and check for DTCs. Repair is complete if no DTCs are stored. Are any DTCs displayed on scan tool? If yes, go to next step. If no, go to step 2 .
15. With a scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Check for the following conditions

1. If DTCs P0105, P0110, P0115, and P0120 are also set, the malfunction may be in a sensor ground circuit.
2. If DTCs P0115 and P0116 are both set the ECT sensor circuit may be open or shorted. Perform the DTC P0115 diagnostic procedure first.
3. Check for proper operation of engines cooling system, including correct coolant level.
4. A faulty thermostat that stays open slightly can cause DTC P0116 to set in cold weather when vehicle is started and let sit while warming up. Replace any suspect thermostat.
5. Use Temperature vs. Resistance table to evaluate the possibility of a shifted ECT sensor. A shifted sensor could result in DTC P0116. See «TEMPERATURE VS. RESISTANCE»(ref-152429-S40771357512003021200000) table.
6. Check for a faulty electrical connection to PCM.

An intermittent malfunction may be caused by a fault in ECT sensor electrical circuit. Check wiring harness and components for an intermittent condition. See

INTERMITTENTS

in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Repair any electrical circuit faults that were found. If DTC P0116 cannot be duplicated, information included in freeze frame data can be useful in determining the vehicle operating conditions when the DTC was first set.

The ignition switch is in RUN position.

1. TP sensor input to PCM is less than 0.1 volt for more than 5 seconds or TP sensor input to PCM is more than 4.9 volts for more than 5 seconds.
2. Above condition is met for more than 5 seconds.

1. PCM illuminates Malfunction Indicator Light (MIL).
2. PCM stores conditions that were present when DTC set as freeze frame data.
3. TP sensor angle will default to zero percent.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run, and fault condition is no longer present.
2. A DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. With throttle closed, select TP sensor parameter on scan tool. Is TP sensor percentage 7-11 percent? If yes, go to next step. If no, go to step 4 .
3. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within freeze frame conditions as specified. Does DTC P0120 set? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(ref-152429-S06321123882003020400000) .
4. Is a DTC P0110 or DTC P0115 also set? If yes, go to step 13 . If no, go to next step.
5. Observe TP sensor parameter with throttle closed. Is TP sensor percentage near 99 percent? If yes, go to step 10 . If no, go to next step.
6. Observe TP sensor parameter with throttle closed. Is TP sensor percentage less than 2 percent? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(ref-152429-S06321123882003020400000) .
7. Disconnect TP sensor harness connector. Jump 5-volt reference circuit and TP sensor input circuit together at TP sensor harness connector. Select TP sensor on scan tool. Is TP sensor percentage more than 90 percent? If yes, go to step 16 . If no, go to next step.
8. Connect a test light between battery voltage and TP sensor input circuit at TP sensor harness connector. Observe TP sensor on scan tool. Is TP sensor percentage more than 90 percent? If yes, go to next step. If no, go to step 14 .
9. Check TP sensor 5-volt reference circuit for an open. Repair as necessary. Did you find and repair a condition? If yes, go to step 20 . If no, go to step 18 .
10. Disconnect TP sensor harness connector. Observe TP sensor parameter on scan tool. Is TP sensor percentage at zero percent? If yes, go to next step. If no, go to step 12 .
11. Connect a test light between battery voltage and TP sensor ground circuit. Did test light illuminate? If yes, go to step 17 . If no, go to step 15 .
12. Check for a short to voltage in TP sensor input circuit. Repair as necessary. Did you find and repair a condition? If yes, go to step 20 . If no, go to step 19 .
13. Check for an open in TP sensor ground circuit between splice S108 and PCM. Repair as necessary. Did you find and repair a condition? If yes, go to step 20 . If no, go to step 18 .
14. Check TP sensor input circuit for an open or a short to ground. Repair circuit as necessary. Did you find and repair a condition? If yes, go to step 20 . If no, go to step 18 .
15. Repair open in TP sensor ground circuit between sensor and splice S108. After repair, go to step 20 .
16. Check for an intermittent or a poor electrical connection at TP sensor. Repair as necessary. Did you find and repair a condition? If yes, go to step 20 . If no, go to next step.
17. Replace TP sensor. After repair, go to step 20 .
18. Check for an intermittent or a poor electrical connection at PCM. Repair as necessary. Did you find and repair a condition? If yes, go to step 20 . If no, go to next step.
19. Replace PCM. After repair, go to step 20 .
20. With a scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that you have not diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no DTCs are present, system is okay at this time.

1. If DTCs P0110, P0115, and P0120 are also set, malfunction may be in the sensor ground circuit.
2. On a good TP sensor, scan tool will typically display a TP angle of 8-10 percent at idle, and 76-77 percent at Wide Open Throttle (WOT).
3. An intermittent malfunction may be caused by fault in the TP sensor electrical circuit. Check wiring harness and components for an intermittent condition. See «INTERMITTENTS»(ref-153013-S39990244982003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.
4. Repair any electrical circuit faults found.
5. Information included in freeze frame data can be useful in determining vehicle operating conditions when DTC first set.

1. Engine speed is increasing.
2. Engine is operating in Closed Loop.

1. Vehicle speed has exceeded 19 mph (30 km/h), and output value of TP sensor is out of applicable range.

1. PCM illuminates Malfunction Indicator Light (MIL) during second key cycle in which the Diagnostic Trouble Code (DTC) sets.
2. PCM stores the conditions which were present when DTC set as freeze frame data.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
2. A DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition switch to RUN position, engine OFF. Install scan tool. Select TP ANGLE parameter. Monitor scan tool while depressing accelerator pedal, repeat procedure several times. Does TP angle value increase steadily when accelerator pedal is depressed and decrease steadily when pedal is released, within specified range? If yes, go to next step. If no, go to step 4 .
3. Use scan tool to clear DTCs. Place vehicle into CHECK MODE operation, using scan tool. See «SERVICE BAY TESTS»(ref-152429-S19809249722003021000000) under SELF-DIAGNOSTIC SYSTEM. Operate vehicle within freeze frame conditions as specified. Does DTC P0121 set? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(ref-152429-S00208255432003020400000) .
4. Connect DVOM between TP sensor reference voltage circuit on harness side and ground. Turn ignition switch to RUN position, engine OFF. Is TP sensor voltage at zero volts? If yes, go to next step. If no, go to step 6 .
5. Connect a test light between reference voltage circuit and ground. Turn ignition switch to RUN position, engine OFF. Does test light illuminate at least dimly? If yes, go to step 7 . If no, go to step 9 .
6. Check for the following conditions: A short to voltage in TP sensor input circuit. Proper mating of TP sensor harness connectors. Repair as necessary. After repair, go to step 12 .
7. Connect a test light between TP sensor input circuit and TP sensor reference voltage circuit at harness connector. Monitor TP angle on scan tool. Is TP sensor percentage more than 90 percent? If yes, go to step 10 . If no, go to next step.
8. Check for the following conditions: High resistance in TP sensor ground circuit between sensor and splice S206. High resistance in TP sensor input circuit between TP sensor and PCM. Repair as necessary. Was a repair necessary? If yes, go to step 12 . If no, go to step 11 .
9. Locate and repair high resistance in reference voltage circuit of TP sensor. After repair, go to step 12 .
10. Replace TP sensor. After repair, go to step 12 .
11. Replace PCM. After repair, go to next step.
12. Use scan tool to clear DTCs. Turn ignition OFF for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S26896539502003020400000) Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
13. With a scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that you have not diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Check throttle valve linkage and lever assembly for free and normal movement. Binding or misalignment of throttle valve can affect TP sensor input. Ensure throttle lever has not been bent or tampered with. Ensure throttle valve opens fully, and lever contacts throttle stop.

On a good TP sensor, scan tool will typically display a TP angle of 8-10 percent at idle, and 76-77 percent at Wide Open Throttle (WOT). An intermittent malfunction may be caused by fault in TP sensor electrical circuit. Check wiring harness and components for an intermittent condition. Repair any electrical circuit faults that were found. Information included in freeze frame data can be useful in determining vehicle operating conditions when DTC first set.

1. Engine coolant temperature (ECT) is at least 158°F (70°C).
2. Engine has been running for at least 180 seconds.
3. Engine speed is at least 1500 RPM.
4. Vehicle speed is 25-62 MPH (40-100 km/h).
5. Throttle Position (TP) sensor input is more than 15 percent.

HO2S 1 output does not indicate rich, more than 450 mV, for more than 1.5 minutes.

1. PCM illuminates Malfunction Indicator Light (MIL) during second key cycle in which DTC sets.
2. PCM stores conditions which were present when DTC set as freeze frame data.

1. PCM turns OFF MIL on the third consecutive trip cycle during which diagnostic has been run and fault condition is no longer present.
2. DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using the scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Start engine. Run engine until it reaches normal operating temperature. Select HO2S 1 parameter on scan tool. Snap throttle. Observe HO2S 1 parameter. Does HO2S 1 voltage vary within 200-900 mV? If yes, go to next step. If no, go to step 4 .
3. Use scan tool to clear DTCs. Place vehicle into CHECK MODE, using scan tool. See «SERVICE BAY TESTS»(ref-152429-S19809249722003021000000) . Operate vehicle within freeze frame conditions as specified. Does DTC P0125 set? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(ref-152429-S37265192682003020400000) .
4. Disconnect HO2S 1 harness connector located behind front floor console. Turn ignition switch to RUN position, engine OFF. Select DMM to measure DC millivolts. Place positive lead of DMM on positive battery voltage, and negative lead on HO2S 1 input circuit terminal on engine harness side. Observe HO2S 1 voltage on scan tool. Is voltage more than 1155 mV? If yes, go to next step. If no, go to step 6 .
5. Connect a test light to battery voltage. Probe HO2S 1 ground circuit terminal on engine harness side. Does test light illuminate? If yes, go to step 8 . If no, go to step 7 .
6. Check for an open or short in HO2S 1 input circuit between HO2S 1 and PCM connector. Repair as necessary. Did you find and repair a condition? If yes, go to step 11 . If no, go to step 10 .
7. Repair open in HO2S 1 ground circuit between HO2S 1 and ground point G104. After repair, go to step 11 .
8. Before replacing oxygen sensor, check for the following conditions: Lean or rich fueling condition. Vacuum leaks. Exhaust leaks. An intermittent or a poor electrical connection at HO2S. Refer to «DIAGNOSTIC AIDS»(ref-152429-S37265192682003020400000) for a complete list of items to check and test. Repair any condition found as necessary. Did you find and repair a condition? If yes, go to step 11 . If no, go to next step.
9. Replace HO2S 1. After replacing sensor, go to step 11 .
10. Replace PCM. After replacing PCM, go to next step.
11. Use scan tool to clear DTCs. Turn ignition OFF for 30 seconds. Start engine. Operate vehicle within Conditions for Running DTC as specified in supporting text. See «CONDITIONS FOR RUNNING DTC»(ref-152429-S21162446252003020400000) . Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
12. Using scan tool, observe the stored information, CAPTURE INFO. Does scan tool display any DTCs that you have not diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Scan tool output control feature, Fuel Injector Modification, can be used at idle to check oxygen sensor performance. Increasing Fuel Injector Modification Commanded State to 25 percent should cause HO2S 1 voltage to exceed 800 mV. Decreasing Fuel Injector Modification Commanded State to - 12 percent should cause HO2S 1 voltage to drop to less than 100 mV. An oxygen sensor that fails to respond accordingly may be faulty or contaminated. When performing Fuel Injector Modification with scan tool, Loop Status will remain Open Loop and Short Term FT will be fixed at zero percent.

Check for any of the following conditions

1. Any damaged oxygen sensor wiring. Sensor pigtail may be improperly routed and contacting exhaust system.
2. An incorrect fuel pressure. A condition that causes a lean exhaust can cause DTC P0125 to set. System will go lean if fuel pressure is too low. PCM can compensate for some decrease. However, if fuel pressure is too low, DTC P0125 may be set. See «FUEL SYSTEMS»(ref-152779-S16928737762003022500000) in SYSTEM & COMPONENT TESTING - 1.8L VIBE article.
3. Lean fuel injectors. See «FUEL INJECTOR BALANCE TEST WITH SPECIAL TOOL»(ref-152779-S08897027942003022500000) in FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 1.8L VIBE article.
4. Any vacuum leaks. Check for incorrectly routed, damaged, or loose vacuum lines and hoses. Check for vacuum leaks at intake manifold, throttle body, and crankcase ventilation system.
5. Any exhaust leaks. An exhaust leak may cause outside air to be pulled into the exhaust gas stream past the HO2S, causing DTC P0125 to set. Check for exhaust leaks near HO2S 1.
6. Any fuel contamination. Water, even in small amounts, can be delivered to fuel injectors. Water can cause a lean exhaust to be indicated. Excessive alcohol in the fuel can also cause this condition.

An intermittent malfunction may be caused by fault in the HO2S circuit sensor electrical circuit. Check the wiring harness and components for an intermittent condition. Repair any electrical circuit faults that were found. The information included in freeze frame data can be useful in determining vehicle operating conditions when the DTC first set.

1. Engine coolant temperature is 50-68°F (10-20°C).
2. Intake Air Temperature (IAT) is 14-97°F (-9 to 36°C).

The engine coolant temperature failed to reach at least 167°F (75°C) during running of water temperature counter diagnostic.

1. PCM illuminates Malfunction Indicator Light (MIL).
2. PCM records operating conditions at time the diagnostic fails. This information is stored in freeze frame buffer.

1. MIL turns OFF after 3 consecutively passing trips without a fault present.
2. A History DTC clears after 40 consecutive warm-up cycles without a fault.
3. Use scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Allow engine to cool to ambient temperature. Turn ignition switch to RUN position, engine OFF. Compare ECT sensor temperature reading to IAT sensor temperature reading on a scan tool. Are ECT and IAT readings within 2 or 3 degrees of each other? If yes, go to next step. If no, go to step 6 .
3. Start the engine and immediately observe ECT parameter on the scan tool. Continue to observe ECT while idling the engine for 10 minutes. Does ECT indicated on scan tool increase by more than 36°F (20°C) within 10 minutes? If yes, go to step 5 . If no, go to next step.
4. Are any ECT sensor DTCs set? If yes, go to «DTC P0115: ECT SENSOR CIRCUIT»(ref-152429-S24935653322003020400000) or «DTC P0116: ECT SENSOR CIRCUIT PERFORMANCE»(ref-152429-S29245533032003020400000) . If no, go to step 8 .
5. Fault is not present. Are there any DTCs stored that have not been diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, go to «DIAGNOSTIC AIDS»(ref-152429-S04758786592003020400000) .
6. Measure resistance of ECT sensor with a DMM. Compare measured resistance of ECT sensor with resistance values in Temperature vs. Resistance table. See «TEMPERATURE VS. RESISTANCE»(ref-152429-S40771357512003021200000) table. Is resistance of ECT sensor within specifications? If yes, go to next step. If no, go to step 9 .
7. Check for any of the following conditions: A high resistance in ECT sensor wiring. A poor connection at ECT sensor. A poor connection at PCM. Repair as necessary. Did you find and correct the condition? If yes, go to step 11 . If no, go to step 10 .
8. Check engine cooling system for all of the following: Correct coolant level. Correct operation of cooling system. Correct operation of thermostat. Repair as necessary. After repair, go to step 11 .
9. Replace ECT sensor. After replacing sensor, go to step 11 .
10. Replace PCM. After replacing PCM, go to step 11 .
11. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S07209311532003020400000) . Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
12. With a scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Check for the following conditions

1. A faulty thermostat that stays open slightly can cause DTC P0128 to set in cold weather when vehicle is started and allowed to sit while warming up. Replace any suspect thermostat.
2. An incorrect thermostat can cause engine to warm up slowly. Replace any thermostat that does not meet OEM specifications.
3. Use Temperature vs. Resistance table to evaluate possibility of a shifted ECT sensor. A shifted sensor could result in DTC P0128. See «TEMPERATURE VS. RESISTANCE»(ref-152429-S40771357512003021200000) table.
4. Check for proper operation of engine cooling system, including correct coolant level.
5. Check for a faulty electrical connection to PCM.

If DTC P0128 cannot be duplicated, information included in freeze frame data can be useful in determining vehicle operating conditions when DTC was first set.

1. Engine coolant temperature is more than 158°F (70°C).
2. Engine is running at idle.

1. HO2S 1 output voltage is always more than 40 mV.
2. HO2S 1 output voltage is always less than 55 mV.

1. PCM illuminates Malfunction Indicator Light (MIL) after 2 consecutive ignition cycles in which diagnostic runs with fault active.
2. PCM records operating conditions at the time diagnostic fails. This information is stored in freeze frame buffer.

1. MIL turns OFF after 3 consecutively passing trips without a fault present.
2. A History DTC clears after 40 consecutive warm-up cycles without a fault.
3. Use scan tool CLEAR DTC INFORMATION function to clear the DTC.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Start engine, and allow engine to reach normal operating temperature. Select HO2S 1 parameter on scan tool. Snap the throttle. Observe HO2S 1 parameter. Does HO2S 1 voltage vary within 200-900 mV? If yes, go to next step. If no, go to step 4 .
3. Use scan tool to clear DTCs. Place vehicle into CHECK MODE, using scan tool. See «SERVICE BAY TESTS»(ref-152429-S19809249722003021000000) under SELF-DIAGNOSTIC SYSTEM. Operate vehicle within freeze frame conditions as specified or until HO2S/O2S test is complete. Did DTC P0130 set? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(ref-152429-S29076729212003021300000) .
4. Disconnect HO2S 1 4-pin harness connector, located behind front floor console. Turn ignition switch to RUN position, engine OFF. Set DMM to measure DC millivolts. Place the positive lead of DMM on positive battery voltage, and negative lead on HO2S 1 input circuit terminal on engine harness side. Observe HO2S 1 parameter on scan tool. Is voltage more than 1155 mV? If yes, go to next step. If no, go to step 6 .
5. Connect a test light to battery voltage. Probe HO2S 1 sensor ground circuit terminal (engine harness side). Does test light illuminate? If yes, go to step 8 . If no, go to step 7 .
6. Check for an open or short in HO2S 1 input circuit between HO2S 1 and PCM connector. Repair as necessary. Did you find and repair a condition? If yes, go to step 11 . If no, go to step 10 .
7. Repair open in HO2S 1 ground circuit between HO2S 1 and ground point G104. After repair, go to step 11 .
8. Before replacing the oxygen sensor check for the following conditions: Lean or rich fueling condition. Vacuum leaks. Exhaust leaks. See «DIAGNOSTIC AIDS»(ref-152429-S29076729212003021300000) for a complete list of items to check and test. An intermittent or a poor electrical connection at HO2S. Repair any condition found as necessary. Did you find and repair a condition? If yes, go to step 11 . If no, go to next step.
9. Replace HO2S 1. After repair, go to step 11 .
10. Replace PCM. After repair, go to next step.
11. Use scan tool to clear DTCs. Turn ignition OFF for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING THE DTC»(ref-152429-S12745810432003020400000) or until HO2S/O2S test is complete. Did DTC run and pass? If yes, go to next step. If no, go to step 2 .
12. With a scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

A DTC P0130 is more likely to set during city driving. Avoid operating vehicle on the highway when validating a DTC P0130.

Scan tool output control feature, Fuel Injector Modification, can be used at idle to check oxygen sensor performance. Increasing Fuel Injector Modification Commanded State to 25 percent should cause HO2S 1 voltage to exceed 800 mV. Decreasing Fuel Injector Modification Commanded State to - 12 percent should cause HO2S 1 voltage to drop to less than 100 mV. An oxygen sensor that fails to respond accordingly may be faulty or contaminated. When performing a Fuel Injector Modification using a scan tool, loop status will remain open loop and short term FT will be fixed at zero percent.

If a DTC P0130 is intermittent, driving vehicle under the conditions outlined in INSPECTION/MAINTENANCE PROCEDURES, can verify whether the fault is present. See INSPECTION/MAINTENANCE HEATED OXYGEN SENSOR/OXYGEN SENSOR (HO2S/O2S) SYSTEM SET PROCEDURE under INSPECTION/MAINTENANCE PROCEDURES. Check for any of the following conditions

1. Misrouted heated oxygen sensor wiring. The sensor pigtail may be misrouted and contacting exhaust system causing a short to ground.
2. Verify PCM to engine electrical grounds are okay.
3. An incorrect fuel pressure. Fuel system can go lean if fuel pressure is too low and DTC P0130 may be set. See «FUEL SYSTEMS»(ref-152779-S16928737762003022500000) in SYSTEM & COMPONENT TESTING - 1.8L VIBE article.
4. An incorrectly calibrated fuel injector.
5. Any vacuum leaks. Check for disconnected or damaged vacuum hoses and for vacuum leaks at intake manifold, throttle body, and crankcase ventilation system.
6. Any exhaust leaks near the HO2S. An exhaust leak may cause outside air to be pulled into the exhaust gas stream and past the HO2S. Outside air may cause DTC P0130 to set.
7. A shorted HO2S. A HO2S that is shorted to ground will display less than 0.1 volt on scan tool. An HO2S that is shorted to voltage will display a reading of more than 1.0 volt on scan tool. Water contamination of HO2S can cause a low or high HO2S voltage to be indicated. A DTC P0130 that occurs more frequently when driving through standing water or when operating vehicle in wet driving conditions can indicate water intrusion. Replace HO2S if sensor is adversely affected by moisture.
8. A contaminated HO2S. Silicone contamination of HO2S can cause a low signal voltage to be indicated. Silicone contamination is indicated by a powdery white deposit on the portion of HO2S exposed to the exhaust stream. Before replacing the HO2S, determine the cause of contamination and correct the condition.
9. Fuel contamination. Small amounts of water can be delivered to fuel injectors and cause a lean exhaust indication. A lean exhaust indication can also be caused by too much alcohol in the fuel.
10. A faulty electrical connection to the PCM.
11. A saturated Evaporative Emission (EVAP) canister or a faulty EVAP purge control. See «EMISSION SYSTEMS & SUBSYSTEMS»(ref-152779-S12716850362003022500000) in SYSTEM & COMPONENT TESTING - 1.8L VIBE article.

An intermittent malfunction may be caused by a fault in the HO2S 1 electrical circuit. Check wiring harness and components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Repair any electrical circuit faults that were found. The information included in freeze frame data can be useful in determining the vehicle operating conditions when the DTC first set.

1. Engine coolant temperature is more than 158°F (70°C).
2. Engine is running at idle.

1. Response time necessary for HO2S voltage to change from rich-to-lean, or from lean-to-rich, is one second or more.

1. PCM illuminates Malfunction Indicator Light (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with fault active.
2. PCM records the operating conditions at the time the diagnostic fails. This information is stored in freeze frame buffer.

1. MIL turns OFF after 3 consecutively passing trips without a fault present.
2. A History DTC clears after 40 consecutive warm-up cycles without a fault.
3. Use scan tool CLEAR DTC INFORMATION function to clear DTC.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Use scan tool to clear DTCs. Using scan tool, place vehicle into CHECK MODE. See «SERVICE BAY TESTS»(ref-152429-S19809249722003021000000) under SELF-DIAGNOSTIC SYSTEM. Operate vehicle within freeze frame conditions as specified, or until HO2S/O2S test is complete. Did DTC P0133 set? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(ref-152429-S28091967742003021300000) .
3. Visually and physically Check the following items: HO2S 1 is securely installed. Any corrosion on terminals. Proper terminal tension at HO2S 1 and at PCM. Any damaged wiring. Repair as necessary. Was a repair necessary? If yes, go to step 11 . If no, go to next step.
4. Check exhaust system for an exhaust leak near engine. Repair as necessary. Was an exhaust leak found? If yes, go to step 11 . If no, go to next step.
5. Disconnect HO2S 1 4-pin harness connector, located behind front floor console. Turn ignition switch to RUN position, engine OFF. Set a DVOM to measure DC millivolts (mV). Place positive lead of DMM on positive battery voltage, and negative lead on HO2S 1 sensor input circuit terminal on engine harness side. Observe HO2S 1 parameter on scan tool. Is the voltage more than 1155 mV? If yes, go to next step. If no, go to step 7 .
6. Connect a test light to battery voltage. Probe the HO2S 1 ground circuit terminal at the HO2S connector on the engine harness side. Does the test light illuminate? If yes, go to step 9 . If no, go to step 8 .
7. Check for an open or a short in HO2S 1 input circuit between HO2S 1 and PCM connector. Repair as necessary. Was a repair necessary? If yes, go to step 11 . If no, go to step 10
8. Repair open in HO2S 1 ground circuit between HO2S 1 and ground point G104. After repair, go to step 11 .
9. Check for, and repair any possible causes of HO2S contamination including the following possible causes: Fuel contamination. Use of an improper RTV sealant. Engine oil or coolant consumption. Replace HO2S 1. After repair, go to step 11 .
10. Replace PCM. After repair, go to next step.
11. Use scan tool to clear DTCs. Turn ignition OFF for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S10026078592003020400000) or until HO2S/O2S test is complete. Did DTC run and pass? If yes, go to next step. If no, go to step 2 .
12. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no DTCs are set, system is okay at this time.

Check for a contaminated HO2S. Silicone contamination of HO2S can cause a low signal voltage to be indicated. Silicone contamination is indicated by a powdery white deposit on portion of HO2S exposed to exhaust stream. Before replacing HO2S determine cause of contamination and correct the condition.

If a DTC P0133 is intermittent, driving vehicle under conditions outlined in INSPECTION/MAINTENANCE EVAP SYSTEM SET PROCEDURE , can verify whether fault is present. See INSPECTION/MAINTENANCE HEATED OXYGEN SENSOR/OXYGEN SENSOR (HO2S/O2S) SYSTEM SET PROCEDURE under INSPECTION/MAINTENANCE PROCEDURES (DRIVE CYCLES). An intermittent malfunction may be caused by fault in the HO2S 1 electrical circuit. Check wiring harness and components for any intermittent conditions. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Information included in freeze frame data can be useful in determining vehicle operating conditions when DTC first set.

1. Engine is running.

1. HO2S heater current exceeds 2 amps.
2. HO2S heater current is 0.2 amp or less.

1. MIL turns OFF after 3 consecutively passing trips without a fault present.
2. PCM records operating conditions at the time the diagnostic fails. This information is stored in freeze frame buffer.
3. PCM will turn OFF the heater in the oxygen sensor.

1. MIL turns OFF after 3 consecutively passing trips without a fault present.
2. A History DTC clears after 40 consecutive warm-up cycles without a fault.
3. Use scan tool CLEAR DTC INFORMATION function to clear DTC.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Use scan tool to clear DTCs. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S23368058322003020400000) or until the HO2S heater test is complete. Did a DTC P0135 or P0141 set? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(ref-152429-S21571271932003021300000) .
3. Turn ignition switch to RUN position, with engine OFF. Disconnect harness connector of the HO2S that failed the diagnostic. Using a test light connected to ground, probe ignition positive voltage circuit, on the engine harness side. Does the test light illuminate? If yes, go to next step. If no, go to step 8 .
4. Turn ignition switch to RUN position, with engine OFF. Using a test light connected to battery positive, probe the heater control circuit on the engine harness side. Does the test light illuminate? If yes, go to step 6 . If no, go to next step.
5. Start and idle the engine. Does the test light illuminate? If yes, go to step 9 . If no, go to step 7 .
6. Check the HO2S heater control circuit for a short to ground. Repair as necessary. Was a repair necessary? If yes, go to step 12 . If no, go to step 11 .
7. Check for an open in HO2S heater control circuit. Repair as necessary. Was a repair necessary? If yes, go to step 12 . If no, go to step 11 .
8. Check for an open in the ignition feed circuit. Repair as necessary. After repair, go to step 12 .
9. Check electrical connections at HO2S for poor connection. Repair as necessary. Was a repair necessary? If yes, go to step 12 . If no, go to step 11 .
10. Replace HO2S. After repair, go to step 12 .
11. Replace PCM. After repair, go to step 12 .
12. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S23368058322003020400000) or until HO2S Heater test is complete. Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
13. With a scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Check for any of the following conditions

1. If a DTC P0135 or DTC P0141 is intermittent, driving vehicle under conditions outlined in Inspection/Maintenance (I/M) section can verify whether fault is present. See «INSPECTION/MAINTENANCE (I/M) HEATED OXYGEN SENSOR (HO2S) HEATER SYSTEM SET PROCEDURE»(ref-152429-S09593335592003020400000) under INSPECTION/MAINTENANCE PROCEDURES (DRIVE CYCLES).
2. HO2S heater diagnostic checks for many faults that can cause DTC P0135 or P0141 to set. If HO2S heater test passes, the cause of the DTC is probably intermittent. Use scan tool to clear DTCs. Road test vehicle while monitoring HO2S heater test in I/M SYSTEM INFORMATION selection on scan tool. When HO2S heater test indicates complete with a YES status, check for a DTC P0135 or P0141 under LAST TEST FAILED. If there is no DTC P0135 or P0141 indicated, DTC is intermittent and HO2S heater diagnostic is indicating okay at this time.
3. An intermittent malfunction may be caused by a fault in HO2S 1 sensor electrical circuit. Check wiring harness and components for an intermittent condition. See «INTERMITTENTS»(ref-153013-S39990244982003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.
4. Repair any electrical circuit faults found.

1. Engine coolant temperature is 158°F (70°C) or more.
2. Vehicle speed is 25 MPH (40 km/h) or more.

Minimum voltage is more than 500 mV for 4 seconds, while operating in fuel cutoff mode.

1. HO2S 2 voltage is 400 mV or more during running of diagnostic test.
2. HO2S 2 voltage is 500 mV or less during running of diagnostic test.

1. PCM illuminates Malfunction Indicator Light (MIL) during the second key cycle in which DTC sets.
2. PCM stores conditions which were present when DTC set as freeze frame data.
3. PCM will turn HO2S 2 heater OFF.

1. PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. A DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Use scan tool to clear DTCs. Using scan tool, place the vehicle into CHECK MODE. See «SERVICE BAY TESTS»(ref-152429-S19809249722003021000000) under SELF-DIAGNOSTIC SYSTEM. Operate vehicle within freeze frame conditions as noted. Does DTC P0136 set? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(ref-152429-S37302637192003021300000) .
3. Remove the rear floor console to gain access to the HO2S 2 electrical connector. Disconnect the HO2S 2 connector. Turn ignition switch to RUN position, with engine OFF. Set a DVOM to measure DC millivolts. Place the positive lead of the DMM on battery positive voltage, and the negative lead on the HO2S 2 sensor input circuit terminal (body harness side). Observe the HO2S 2 scan tool parameter. Is the voltage near 1155 mV? If yes, go to next step. If no, go to step 5 .
4. Connect a test light to battery voltage. Probe HO2S 2 sensor ground circuit terminal at the HO2S connector on the body harness side. Does the test light illuminate? If yes, go to step 7 . If no, go to step 6 .
5. Check for an open or short in the HO2S 2 input circuit between the HO2S 2 and the PCM connector. Repair as necessary. Was a repair necessary? If yes, go to step 9 . If no, go to step 8 .
6. Repair open in HO2S 2 ground circuit between HO2S 2 and ground point G104. After repair, go to step 9 .
7. Replace HO2S 2. After repair, go to step 9 .
8. Replace PCM. After repair, go to step 9 .
9. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S33178550062003020400000) . Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
10. Using a scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Check for the following conditions

1. Check wiring harness for damage. If harness appears to be OK, observe HO2S 2 display on scan tool while moving connectors and wiring harnesses related to the sensor. A change in HO2S 2 display will indicate location of the fault.
2. If a DTC P0136 is intermittent, driving vehicle under the conditions outlined in Inspection/Maintenance (I/M) procedures can verify whether the fault is present. See «INSPECTION/MAINTENANCE HEATED OXYGEN SENSOR/OXYGEN SENSOR (HO2S/O2S) SYSTEM SET PROCEDURE»(ref-152429-S08094873662003020400000) under INSPECTION/MAINTENANCE PROCEDURES (DRIVE CYCLES).
3. An intermittent malfunction may be caused by fault in the HO2S circuit sensor electrical circuit. Check the wiring harness and components for an intermittent condition. See «INTERMITTENTS»(ref-153013-S39990244982003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.
4. Repair any electrical circuit faults found. The information included in freeze frame data can be useful in determining vehicle operating conditions when DTC first set.

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
2. System voltage is 9-18 volts.
3. Closed Loop commanded air/fuel ratio is 14.5-14.8.
4. Throttle angle is 3-40 percent.

HO2S 2 signal voltage remains greater than 975 mV during closed loop operation for longer than 45 seconds or HO2S 2 signal voltage remains greater than 200 mV during Decel Fuel Cut-Off (DFCO) operation, with either conditions present for up to 5 minutes.

1. PCM illuminates Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. PCM records operating conditions at the time the diagnostic fails. The first time the diagnostic fails, PCM stores this information in failure records. If the diagnostic reports a failure on the second consecutive ignition cycle, PCM records operating conditions at the time of the failure. PCM writes operating conditions to freeze frame and updates failure records.

1. PCM turns OFF MIL after 3 consecutive ignition cycles that the diagnostic runs and passes.
2. A current, DTC last test fails, clears when the diagnostic runs and passes.
3. A DTC stored in history clears after 40 warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. A scan tool can be used to clear DTC.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Did DTC P0140 also set? If yes, go to «DTC P0140: HO2S 2 CIRCUIT INSUFFICIENT ACTIVITY (BANK 1)»(ref-152429-S40889307102003020400000) . If no, go to next step.
3. Allow engine to idle at operating temperature. Clear DTC and record freeze frame/failure records data if HO2S 1 voltage is fixed at bias voltage. Vary engine speed from idle to 3000 RPM several times within 5 seconds. Observe HO2S 2 voltage parameter with a scan tool. Did HO2S 2 voltage remain greater than 975 mV? If yes, go to step 5 . If no, go to next step.
4. Observe freeze frame/failure records data for this DTC. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S23428551122003020400000) or as close to freeze frame/failure records data observed. Does DTC fail this ignition? If yes, go to next step. If no, see «INTERMITTENTS»(ref-153013-S39990244982003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.
5. Turn ignition OFF. Disconnect HO2S 2 4-pin harness connector. Connect a 3-amp fused jumper wire between HO2S 2 low signal circuit and a good ground. Turn ignition switch to RUN position, engine off. Observe HO2S 2 voltage parameter using a scan tool. Does HO2S voltage read more than 975 mV? If yes, go to next step. If no, go to step 7 .
6. Check HO2S 2 high signal circuit for a short to voltage. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 9 .
7. Check for the following conditions that may affect the HO2S operation: HO2S for contamination, chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring. Exhaust system leaks or restrictions. EVAP canister purge. Proper fuel pressure. Did you find and correct the condition? If yes, go to step 12 . If no, go to next step.
8. Check for poor connections at HO2S 2 connector. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 10 .
9. Check for poor connections at PCM harness connectors. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 11 .
10. Replace HO2S 2. After repair, go to step 12
11. Turn ignition OFF. Replace PCM. After repair, go to next step.
12. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S23428551122003020400000) . Does DTC run and pass? If yes, go to next step. If no, go to step 3 .
13. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay.

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
2. Engine run time is longer than 4 minutes.
3. System voltage is 9-18 volts.
4. Diagnostic runs once per trip.

1. HO2S 2 signal voltage remains between 408-512 mV for more than 90 seconds.
2. There is a Throttle Position (TP) sensor angle change of more than 8 percent, at least twice during test period.

PCM illuminates Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

PCM records the operating conditions at the time diagnostic fails. The first time diagnostic fails, PCM stores this information in failure records. If diagnostic reports a failure on the second consecutive ignition cycle, PCM records operating conditions at the time of the failure. PCM writes operating conditions to freeze frame and updates failure records.

1. PCM turns OFF MIL after 3 consecutive ignition cycles that the diagnostic runs and passes.
2. A current, DTC last test fails, clears when diagnostic runs and passes.
3. A DTC stored in history clears after 40 warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. A scan tool can be used to clear the DTC.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Allow engine to idle at operating temperature. Observe HO2S 2 voltage parameter using a scan tool. Clear DTC and record freeze frame/failure records data if HO2S 2 voltage is fixed at bias voltage. Vary engine speed from idle to 3000 RPM several times within 5 seconds. Does HO2S 2 voltage fluctuate greater than and less than 375-475 mV? If yes, go to next step. If no, go to step 4 .
3. Observe freeze frame/failure records data for this DTC. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S32427335462003020400000) or as close to freeze frame/failure records data observed. Does the DTC fail this ignition? If yes, go to next step. If no, see «INTERMITTENTS»(ref-153013-S39990244982003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.
4. Disconnect HO2S 2 4-pin harness connector. Turn ignition switch to RUN position, engine off. Connect a 3-amp fused jumper wire between HO2S 2 low signal circuit and a good ground. Connect a 3-amp fused jumper wire between the HO2S 2 high signal circuit and a good ground. Observe HO2S 2 voltage parameter using scan tool. Does HO2S 2 voltage measure less than 25 mV? If yes, go to step 7 . If no, go to next step.
5. With the ignition OFF, disconnect PCM harness connectors. Leave HO2S 2 disconnected. Measure resistance of HO2S 2 high signal circuit. Measure resistance of HO2S 2 low signal circuit. Is resistance 0-5 ohms? If yes, go to step 9 . If no, go to next step.
6. Repair appropriate signal circuit that has an open or high resistance condition. After repair, go to step 12 .
7. Check for the following conditions that may affect HO2S operation: HO2S for contamination. Chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring. Exhaust system leaks or restrictions. Chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring. Exhaust system leaks or restrictions. EVAP canister purge. Proper fuel pressure. Did you find and correct the condition? If yes, go to step 12 . If no, go to next step.
8. Check for poor connections at HO2S 2 connector. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 10 .
9. Check for poor connections at PCM harness connectors. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 11 .
10. Replace HO2S 2. After repair, go to step 12 .
11. Turn ignition off. Replace PCM. After repair, go to next step.
12. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S36783712762003020400000) . Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
13. Using a scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay.

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
2. System voltage is 9-18 volts.
3. IAT is less than 35°F (2°C) at start-up.
4. ECT is less than 35°F (2°C) at start-up.
5. IAT and ECT are within 11°F (6°C) of each other at start-up.

HO2S 2 voltage remains within 150 mV of bias voltage, about 450 mV, for a longer amount of time than necessary. Amount of time ranges between 100-130 seconds depending on ECT at start-up and average Mass Airflow (MAF) since start-up.

PCM illuminates Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that diagnostic runs and fails.

PCM records operating conditions at time the diagnostic fails. The first time the diagnostic fails, PCM stores this information in failure records. If the diagnostic reports a failure on the second consecutive ignition cycle, PCM records operating conditions at the time of failure. PCM writes operating conditions to freeze frame and updates failure records.

1. PCM turns OFF MIL after 3 consecutive ignition cycles that the diagnostic runs and passes.
2. A current DTC last test fails clears when the diagnostic runs and passes.
3. A DTC stored in history clears after 40 warm-up cycles if no failures are reported by this or any other emission related diagnostic.
4. A scan tool can be used to clear DTC.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition switch to RUN position, engine off. Monitor HO2S 2 voltage on scan tool. Does HO2S 2 voltage go to greater than or less than the previously stabilized voltage, by at least as much as 100 mV within 2 minutes? If yes, go to next step. If no, go to step 4 .
3. Observe freeze frame/failure records data for this DTC. Turn ignition OFF for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S36783712762003020400000) or as close to freeze frame/failure records data observed. Does DTC fail this ignition? If yes, go to next step. If no, see «INTERMITTENTS»(ref-153013-S39990244982003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.
4. Disconnect HO2S 2 4-pin harness connector. Turn ignition switch to RUN position, engine off. Connect a test light between HO2S 2 heater ignition voltage circuit, in harness side of HO2S connector, and ground. Does the test light illuminate? If yes, go to next step. If no, go to step 7 .
5. Turn ignition OFF. Connect a test light between HO2S 2 heater ignition voltage circuit, in harness side of HO2S connector, and HO2S 2 heater ground circuit. Turn ignition switch to RUN position, engine off. Does test light illuminate? If yes, go to next step. If no, go to step 10 .
6. Turn ignition OFF. Leave HO2S connector disconnected. Allow engine to cool for at least 15 minutes. Measure HO2S 2 heater resistance at HO2S 2 pigtail connector using a Digital Multimeter (DMM). Resistance should be 2-20 ohms? If yes, go to next step. If no, go to step 11 .
7. Check HO2S 2 heater ignition voltage circuit for an open fuse. Did you find an open fuse? If yes, go to next step. If no, go to step 9 .
8. Locate and repair short to ground in HO2S 2 heater ignition voltage circuit and replace fuse. After repair, go to step 13 .
9. Repair open or high resistance condition in HO2S 2 heater ignition voltage circuit. After repair, go to step 13 .
10. Repair open or high resistance condition in HO2S 2 heater ground circuit. After repair, go to step 13 .
11. Before continuing, Check for poor connections at HO2S 2 connector. Did you find and correct the condition? If yes, go to step 13 . If no, go to next step.
12. Replace HO2S 2. After repairs, go to next step.
13. Use scan tool to clear DTCs. Turn ignition OFF for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S36783712762003020400000) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
14. Using a scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay.

1. Engine coolant temperature is more than 158°F (70°C).
2. Engine is running at steady speed.
3. Engine is operating in closed loop.

Fuel trim value is constantly high during stable engine operation.

1. PCM illuminates Malfunction Indicator Light (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with fault active.
2. PCM stores conditions which were present when DTC set as freeze frame data.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. A DTC will clear after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Start engine. Operate vehicle until loop status indicates closed loop. Observe Short Term FT parameter display on scan tool. Is Short Term FT parameter displayed on scan tool less than 20 percent? If yes, see «DIAGNOSTIC AIDS»(ref-152429-S22805819902003020400000) . If no, go to next step.
3. Visually and physically check for any of the following conditions: Splits, kinks, and improper connections in vacuum hoses. Correct installation of PCV valve. Leaks in exhaust system. Did any of the above inspections isolate a condition requiring a repair? If yes, go to step 10 . If no, go to next step.
4. Start engine. Run engine until engine reaches normal operating temperature. Observe operation of the following sensors at idle, with a scan tool: Mass Air Flow (MAF) sensor. Engine Coolant Temperature (ECT) sensor. Throttle Position (TP) sensor. Compare observed sensor readings with Typical Scan Tool Data Values, located in engine scan tool data list. See «SCAN TOOL DATA LIST»(ref-152429-S11741660572003021000000) under SELF-DIAGNOSTIC SYSTEM. Check vehicle for cause of any errant sensor readings and repair as necessary. Was a repair necessary? If yes, go to step 10 . If no, go to next step.
5. Turn ignition switch to OFF position. Install a fuel pressure gauge. See «FUEL GAUGE»(ref-153233-S05610451762003032700000) under FUEL SYSTEMS in REMOVAL & INSTALLATION - 1.8L VIBE article. Observe fuel pressure with engine running at normal operating temperature. Is fuel pressure 44-50 psi (301-347 kPa)? If yes, go to next step. If no, diagnose fuel system. See «FUEL SYSTEMS»(ref-152779-S16928737762003022500000) in SYSTEM & COMPONENT TESTING - 1.8L VIBE article.
6. Check fuel for excessive water, alcohol, or other contaminants. See «ALCOHOL/CONTAMINANTS-IN-FUEL DIAGNOSIS»(ref-152779-S09199734132003022500000) in SYSTEM & COMPONENT TESTING - 1.8L VIBE article. Was the fuel contaminated? If yes, go to next step. If no, go to step 8 .
7. Replace contaminated fuel. After replacement, go to step 10 .
8. Perform Fuel Injector Balance Test. See «FUEL INJECTOR BALANCE TEST WITH SPECIAL TOOL»(ref-152779-S08897027942003022500000) in FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 1.8L VIBE article. Repair or replace as necessary. Was a repair necessary? If yes, go to step 10 . If no, go to next step.
9. Is a lean condition still present? See «SYMPTOM DIAGNOSIS»(ref-153013-S36467972162003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. If no, go to step 10 .
10. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S09532405112003020400000) . Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
11. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no DTCs are displayed, system is okay at this time.

Check for any of the following conditions

1. Vacuum leaks.
2. Exhaust leaks.
3. Correct fuel pressure. Fuel system will be lean if fuel pressure is too low. To determine cause of DTC P0171, monitoring fuel pressure while driving vehicle at various road speeds may be necessary. See «FUEL SYSTEMS»(ref-152779-S16928737762003022500000) in SYSTEM & COMPONENT TESTING - 1.8L VIBE article.
4. Check for fuel contamination. Small amounts of water can be delivered to fuel injectors and cause a lean exhaust indication. A lean exhaust indication can also be caused by too much alcohol in the fuel. See «ALCOHOL/CONTAMINANTS-IN-FUEL DIAGNOSIS»(ref-152779-S09199734132003022500000) in SYSTEM & COMPONENT TESTING - 1.8L VIBE article.
5. A Mass Air Flow (MAF) sensor output that is incorrect may cause PCM to command fuel system to go lean. Check performance of MAF sensor. Check for air restrictions and air inlet leaks near MAF sensor. If HO2S voltage is fixed low, while fuel trim is constantly high, check MAF sensor signal circuit for resistance. High circuit resistance can cause sensor to read a lower volume of air than actual, resulting in a lean fueling condition.
6. Check wiring harness for damage. If harness appears to be OK, observe HO2S 1 display on scan tool while moving connectors and wiring harnesses related to sensor. A change in display will indicate location of fault.
7. Check for a contaminated oxygen sensor. Silicone and other contaminants can cause oxygen sensor to provide false lean exhaust readings. If contamination is found, determine cause of contamination and correct the condition before replacing HO2S.
8. Check for fuel contamination of the crankcase. Fuel that has entered the crankcase can release vapors that enter the engine through the PCV system, thereby causing a rich running condition.
9. Check HO2S 1 for water intrusion into wiring harness and sensor housing. Water can create a short to ground in HO2S signal circuit, causing a false lean indication.
10. Check HO2S 1 and MAF sensor for faulty electrical connections to PCM.

An intermittent malfunction may be caused by a fault in HO2S 1 electrical circuit. Check wiring harness and components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Repair any electrical circuit faults found. If DTC P0171 cannot be duplicated, information included in freeze frame data can be useful in determining vehicle operating conditions when DTC was first set.

1. Engine coolant temperature is more than 158°F (70°C).
2. Engine is running at steady speed.
3. Engine is operating in closed loop.

Fuel trim value is constantly low during stable engine operation.

1. PCM illuminates Malfunction Indicator Light (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with fault active.
2. PCM stores conditions which were present when DTC set as freeze frame data.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. A DTC will clear after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Start engine. Operate vehicle until loop status indicates closed loop. Observe Short Term FT parameter display on scan tool. Is Short Term FT parameter displayed on scan tool more than -20 percent? If yes, go to «DIAGNOSTIC AIDS»(ref-152429-S28137810032003020400000) . If no, go to next step.
3. Visually and physically check air filter and air induction assembly for any of the following conditions: A dirty or contaminated air filter. Any restrictions or blockage of airflow. Any leaks in the exhaust system. Did any of the above checks isolate a condition requiring a repair? If yes, go to next step. If no, go to step 9 .
4. Start engine. Run engine until engine reaches a normal operating temperature. Using a scan tool, observe operation of the following sensors at idle: Mass Air Flow (MAF) sensor. Engine Coolant Temperature (ECT) sensor. Pre-catalyst Heated Oxygen Sensor (HO2S 1). Compare the observed sensor readings with Typical Scan Tool Data Values located in engine scan tool data list. See «SCAN TOOL DATA LIST»(ref-152429-S11741660572003021000000) . Check any errant readings for their cause and repair as necessary. Was a repair necessary? If yes, go to step 9 . If no, go to next step.
5. Turn ignition OFF. Install a fuel pressure gauge. See «FUEL GAUGE»(ref-153233-S05610451762003032700000) under FUEL SYSTEMS in REMOVAL & INSTALLATION - 1.8L VIBE article. Observe fuel pressure with engine running at a normal operating temperature. Is fuel pressure 44-50 psi (301-347 kPa)? If yes, go to next step. If no, diagnose fuel system. See «FUEL SYSTEMS»(ref-152779-S16928737762003022500000) in SYSTEM & COMPONENT TESTING - 1.8L VIBE article.
6. Check Evaporative Emission (EVAP) control system for possible over-purging of EVAP system. See «EVAPORATIVE EMISSION CONTROL SYSTEM DIAGNOSIS»(ref-152779-S17488005022003022500000) in SYSTEM & COMPONENT TESTING - 1.8L VIBE article. Repair as necessary. Was a problem found? If yes, go to step 9 . If no, go to next step.
7. Remove and visually and physically check HO2S 1 for silicone contamination. Contamination will be indicated by a powdery White deposit on the portion of HO2S that is exposed to exhaust stream. If contamination is evident on HO2S, replace contaminated sensor and correct source of contamination. Did HO2S require replacement? If yes, go to step 9 . If no, go to next step.
8. Is a rich condition still present? If yes, see «SYMPTOM DIAGNOSIS»(ref-153013-S36467972162003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. If no, go to next step.
9. Use scan tool to clear DTCs. Turn ignition OFF for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S35651687982003020400000) . Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
10. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no DTCs are displayed, system is okay at this time.

Check for any of the following conditions

1. Check for a restriction in the inlet air passage. A duct or inlet hose that collapses when hot or that is blocked by debris can cause a DTC P0172 to set.
2. Check for correct fuel pressure. Fuel system will be rich if fuel pressure is too high. To determine the cause of a DTC P0172, monitoring fuel pressure while driving vehicle at various road speeds may be necessary. See «FUEL SYSTEMS»(ref-152779-S16928737762003022500000) in SYSTEM & COMPONENT TESTING - 1.8L VIBE article.
3. A MAF sensor output that is incorrect may cause PCM to command fuel system to go rich. Check performance of MAF sensor. Check for air restrictions and for air inlet leaks near MAF sensor.
4. Check for a damaged wiring harness. If harness appears to be OK, observe HO2S 1 display on scan tool while moving connectors and wiring harnesses related to the sensor. A change in display will indicate location of fault.
5. Check for a contaminated oxygen sensor. Silicone and other contaminants can cause oxygen sensor to provide false exhaust oxygen content readings. If contamination is found, determine the cause and correct the condition before replacing HO2S.
6. Check HO2S 1 for water intrusion into the wiring harness and sensor housing. Water can create a short to voltage in HO2S signal circuit, causing a false rich indication.
7. Check HO2S 1 and MAP sensor for a faulty electrical connection to PCM.

An intermittent malfunction may be caused by a fault in HO2S 1 electrical circuit. Check wiring harness and components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Repair any electrical circuit faults found. If a DTC P0172 cannot be duplicated, information included in freeze frame data can be useful in determining vehicle operating conditions when DTC was first set.

1. Engine speed is 400-4000 RPM.
2. Battery voltage is 9-17 volts.
3. Engine coolant temperature is 20-254°F (-7 to 123°C).

Misfire is indicated in more than one cylinder simultaneously.

1. PCM flashes Malfunction Indicator Light (MIL) the first time catalytic converter damage can occur.
2. PCM illuminates MIL the second time the diagnostic fails.
3. PCM records operating conditions at the time the diagnostic fails. This information is stored in freeze frame buffer. PCM also freezes engine speed at MISFIRE and LOAD AT MISFIRE scan tool data parameters at the time MIL illuminates.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. A DTC will clear after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start engine. Monitor TOTAL MISFIRE CURRENT COUNT parameter on scan tool. Did scan tool indicate any misfire counts? If yes, go to step 5 . If no, go to next step.
3. Use scan tool to clear DTCs. Place vehicle into CHECK MODE, using scan tool. See «SERVICE BAY TESTS»(ref-152429-S19809249722003021000000) under SELF-DIAGNOSTIC SYSTEM. Operate vehicle within freeze frame conditions as specified. Monitor TOTAL MISFIRE CURRENT COUNT parameter on scan tool. Did DTC P0300 set or did scan tool indicate any misfire counts? If yes, go to step 5 . If no, go to next step.
4. The fault is not present. Are there any DTCs stored that have not been diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, go to «DIAGNOSTIC AIDS»(ref-152429-S05186635862003020400000) .
5. Disconnect all fuel injector harness connectors. Remove ignition coil 1. Connect ignition coil harness connector. Connect Spark Tester (J 26792), or equivalent, to ignition coil 1 boot. Crank engine and observe spark tester. A crisp, blue spark should be observed. Install ignition coil. Repeat steps 2) through 5) for each remaining ignition coils. Is a crisp blue spark present for each ignition coil? If yes, go to step 7 . If no, go to next step.
6. Turn ignition OFF. Exchange ignition coils. Replace suspected faulty ignition coil with a coil that produced good spark. Connect Spark Tester to the ignition coil boot. Crank engine while observing spark tester. Was a crisp blue spark present? If yes, go to step 14 . If no, go to step 15 .
7. Perform a visual and physical inspection of the ignition coil boots and spark plugs for the following conditions: Any water intrusion. Any corroded or poor connections to the spark plugs. Any carbon tracking. Repair condition or replace faulty coil or spark plug as necessary. See «IGNITION COIL»(ref-153233-S39040543072003032600000) OR «SPARK PLUG»(ref-153233-S34800811732003032800000) under IGNITION SYSTEMS in REMOVAL & INSTALLATION article. Was a repair necessary? If yes, go to step 17 . If no, go to next step.
8. Remove spark plugs. Perform a visual and physical inspection of the spark plugs. Repair or replace as necessary. Was a faulty spark plug condition found and repaired? Go to step 17 . If no, go to next step.
9. Turn ignition OFF. Disconnect all 4 fuel injector harness connectors. Install a Fuel Injector Test Light (J 34730-2B), or equivalent, into each fuel injector harness connector. Observe injector test light for each fuel injector while cranking engine. Does fuel injector test light flash for each injector while cranking the engine? If yes, go to next step. If no, go to «FUEL INJECTOR CIRCUIT DIAGNOSIS»(ref-152779-S28932611062003022500000) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 1.8L VIBE article.
10. Perform FUEL INJECTOR COIL TEST - ENGINE COOLANT TEMPERATURE BETWEEN 50-95°F (10-35°C) and FUEL INJECTOR BALANCE TEST WITH SPECIAL TOOL procedures under FUEL SYSTEMS in «SYSTEM & COMPONENT TESTING - 1.8L VIBE»(ref-152779) article. Did any fuel injectors require replacement? If yes, go to step 17 . If no, go to next step.
11. Turn ignition OFF. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-152779-S28904540322003022500000) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 1.8L VIBE article. Install fuel pressure gauge. See «FUEL GAUGE»(ref-153233-S05610451762003032700000) under FUEL SYSTEMS in REMOVAL & INSTALLATION - 1.8L VIBE article. Install scan tool. Turn ignition switch to RUN position, engine OFF. Select FUEL PUMP in ENGINE OUTPUT CONTROLS menu of scan tool. Turn fuel pump ON, using scan tool. Observe fuel pressure indicated by fuel pressure gauge with fuel pump running. Is fuel pressure 44-50 psi (301-347 kPa)? If yes, go to next step. If no, diagnose fuel system. See «FUEL SYSTEMS»(ref-152779-S16928737762003022500000) in SYSTEM & COMPONENT TESTING - 1.8L VIBE article.
12. Check a fuel sample for any alcohol or other contamination and fuel type and quality. See «ALCOHOL/CONTAMINANTS-IN-FUEL DIAGNOSIS»(ref-152779-S09199734132003022500000) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 1.8L VIBE article. Replace fuel as necessary. Was a repair necessary? If yes, go to step 17 . If no, go to next step.
13. Visually and physically check PCV valve, intake manifold gasket, vacuum lines, vacuum hoses, and fittings for vacuum leaks or for a misrouted vacuum line or hose. Repair as necessary. Did you find and correct a condition? If yes, go to step 17 . If no, go to step 16 .
14. Replace faulty ignition coil. After repair, go to step 17 .
15. Check electrical circuits of faulty ignition coil for the following conditions: An open in ignition coil ground circuit. An open in positive voltage supply circuit. An open in trigger signal circuit. No trigger signal generated by PCM. Repair as necessary. After repair, go to step 17 .
16. Check for any of the following engine mechanical concerns: A worn or faulty camshaft. Any leaky or sticky valves. Any excessive valve deposits. Any weak valve springs. Incorrect valve timing. Faulty rocker arm operation. Any intake manifold runner leaks or obstructions. Any broken or worn piston rings. A leaking head gasket. Repair as necessary. See appropriate article in ENGINES. Was a basic engine mechanical concern found and repaired? If yes, go to step 17 . If no, go to «DIAGNOSTIC AIDS»(ref-152429-S05186635862003020400000) .
17. Use scan tool to clear DTCs. Operate vehicle within freeze frame conditions that set the DTC. Monitor TOTAL MISFIRE CURRENT COUNT parameter on scan tool. Did a DTC set or did scan tool indicate any misfire counts? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no DTCs are displayed, system is okay at this time.

Check for the following conditions

1. If any DTCs other than misfire (P0300 to P0304) are present, diagnose those DTCs first.
2. If DTCs P0301, P0302, P0303, or P0304 are also present with DTC P0300, diagnose those DTCs first.
3. ENGINE SPEED AT MISFIRE and LOAD AT MISFIRE scan tool data parameters are fixed at the time MIL illuminates. These 2 scan tool displays can be used like 2 additional lines of freeze frame data. Review ENGINE SPEED AT MISFIRE and LOAD AT MISFIRE scan tool parameters located in scan tool ENGINE DATA list. The information can help determine vehicle conditions when the misfire occurred.
4. Review misfire counters located in ENGINE DATA LIST of scan tool while engine is running. If TOTAL MISFIRE CURRENT COUNT data parameter is increasing, the misfire condition is present. A current DTC P0300 should indicate misfire activity in TOTAL MISFIRE CURRENT COUNT parameter. Use this information to determine if fault is present or an intermittent malfunction.
5. An intermittent can also be the result of a defective CKP sensor signal rotor. Remove CKP sensor and check the signal rotor through the sensor hole. Check condition of the signal rotor for nicks, dents, missing teeth, and foreign material.
6. A Mass Air Flow (MAF) sensor output that is incorrect may cause PCM to command fuel system to go lean. Check performance of the MAF sensor. If HO2S voltage is fixed low, while fuel trim is constantly high, check MAF sensor signal circuit for resistance. High circuit resistance can cause sensor to read a lower volume of air than actual, resulting in a lean fueling condition that can cause engine misfire.
7. Check for engine overheating.
8. Check for a PCV system malfunction. Perform functional check of PCV valve. See «POSITIVE CRANKCASE VENTILATION»(ref-152779-S00418169322003022500000) under EMISSION CONTROLS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 1.8L VIBE article.

An intermittent malfunction may be caused by a fault in the ignition system or fuel system electrical circuits. Check wiring harness and components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Repair any electrical circuit faults that were found. The information included in freeze frame data can be useful in determining the vehicle operating conditions when DTC first set.

Conditions for Clearing the MIL/DTC

1. PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. A DTC will clear after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Start engine. Monitor MISFIRE CURRENT CYL. NO. data parameter for all engine cylinders on the scan tool. Does scan tool indicate a misfire in any cylinder? If yes, go to step 5 . If no, go to next step.
3. Use scan tool to clear DTCs. Using the scan tool, place vehicle into CHECK MODE. See «SERVICE BAY TESTS»(ref-152429-S19809249722003021000000) under SELF-DIAGNOSTIC SYSTEM. Operate vehicle within freeze frame conditions as specified. Monitor MISFIRE CURRENT CYL. NO. data parameters on scan tool. Is a cylinder specific misfire DTC P0301-P0304 set or does scan tool indicate a misfire in any cylinder? If yes, go to step 5 . If no, go to next step.
4. The fault is not present. Are there any DTCs stored that have not been diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, go to «DIAGNOSTIC AIDS»(ref-152429-S06840761612003021400000) .
5. Is a DTC P1300, P1305, P1310, or P1315 present? If yes, go to «DTC P1300, P1305, P1310, P1315: IGNITION COIL PRIMARY FEEDBACK CIRCUITS»(ref-152429-S09979277982003020400000) . If no, go to next step.
6. Disconnect ignition coil of misfiring cylinder. Remove ignition coil of misfiring cylinder. Connect harness connector of the removed ignition coil. Install Spark Tester (J 26792), or equivalent, at the end of spark plug boot of removed ignition coil. Crank engine while observing spark tester. A crisp, blue spark should be observed. Was a crisp, blue spark present on every engine revolution? If yes, go to step 8 . If no, go to next step.
7. Turn ignition OFF. Exchange ignition coil. Replace ignition coil of suspected faulty cylinder with an ignition coil from a normally operating cylinder. Install spark tester at the end of the spark plug boot of ignition coil. Check for spark as performed in step 6) . Did the test indicate a crisp, blue spark while cranking the engine? If yes, go to step 15 . If no, go to step 16 .
8. Perform a visual and physical inspection of the ignition coil boot for the following conditions: Water intrusion or moisture. A corroded or damaged electrical terminal. Carbon tracking. Repair the condition or replace ignition coil or spark plug as necessary. Was a repair necessary? If yes, go to step 15 . If no, go to next step.
9. Remove spark plug from misfiring cylinders. Check spark plugs for correct operation and good performance. Repair or replace spark plug(s) as necessary. Was a faulty spark plug condition found and repaired? If yes, go to step 18 . If no, go to next step.
10. Turn engine OFF. Disconnect fuel injector of each misfiring cylinder. Install Fuel Injector Test Light (J 34730-2B), or equivalent, into fuel injector harness connector of a misfiring cylinder. Check fuel injector circuit by observing the test light while cranking the engine. Repeat action in step 3) and test in step 4) for each misfiring cylinder. Did the fuel injector test light blink for every test while cranking the engine? If yes, go to next step. If no, go to «FUEL INJECTOR CIRCUIT DIAGNOSIS»(ref-152779-S28932611062003022500000) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 1.8L VIBE article.
11. Perform the Fuel Injector Coil Test and the Fuel Injector Balance Test procedures. See «FUEL INJECTOR COIL TEST - ENGINE COOLANT TEMPERATURE BETWEEN 50-95°F (10-35°C)»(ref-152779-S06830036892003022500000) and «FUEL INJECTOR BALANCE TEST WITH SPECIAL TOOL»(ref-152779-S08897027942003022500000) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 1.8L VIBE article. Did any fuel injectors require replacement? If yes, go to step 18 . If no, go to next step.
12. Turn ignition switch to OFF position. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-152779-S28904540322003022500000) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 1.8L VIBE article. Install a fuel pressure gauge. See «FUEL GAUGE»(ref-153233-S05610451762003032700000) under FUEL SYSTEMS in REMOVAL & INSTALLATION - 1.8L VIBE article. Install scan tool. Turn ignition switch to RUN position, engine OFF. Select FUEL PUMP in ENGINE OUTPUT CONTROLS menu of scan tool. Command fuel pump ON, using scan tool. Observe fuel pressure indicated by fuel pressure gauge with the fuel pump running. Is fuel pressure 44-50 psi (301-347 kPa)? If yes, go to next step. If no, diagnose fuel system. See «FUEL SYSTEMS»(ref-152779-S16928737762003022500000) in SYSTEM & COMPONENT TESTING - 1.8L VIBE article.
13. Check a fuel sample for the following concerns: Excessive alcohol content or contamination. See «ALCOHOL/CONTAMINANTS-IN-FUEL DIAGNOSIS»(ref-152779-S09199734132003022500000) in SYSTEM & COMPONENT TESTING - 1.8L VIBE article. Correct fuel type and quality Replace fuel as necessary. See «FUEL SYSTEM CLEANING»(ref-152779-S16101428252003022500000) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 1.8L VIBE article. Was a repair necessary? If yes, go to step 18 . If no, go to next step.
14. Visually and physically check the following for vacuum leaks: Intake manifold gasket. Vacuum lines, hoses, and fittings. Check for incorrect vacuum hose routing. Repair as necessary. Check PCV system for an incorrectly operating or leaking PCV valve. See «POSITIVE CRANKCASE VENTILATION»(ref-152779-S00418169322003022500000) under EMISSION CONTROLS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTS - 1.8L VIBE article. Replace PCV valve as necessary. Did you replace a part or perform a repair? If yes, go to step 18 . If no, go to step 17 .
15. Replace faulty ignition coil. After repair, go to step 18 .
16. Check malfunctioning ignition coil circuits for the following conditions: An open in ignition coil ground circuit. An open in positive voltage supply circuit. An open in trigger signal circuit. No trigger signal generated by PCM. Repair as necessary. After repair, go to step 18 .
17. Check for the following engine mechanical conditions: A worn or faulty camshaft. Any leaky or sticky valves. Any excessive valve deposits. Any weak valve springs. Incorrect valve timing. Faulty rocker arm operation. An intake manifold runner leak or obstruction. Any broken or worn piston rings. A leaking head gasket. Repair as necessary. Was a basic engine mechanical concern found and repaired? If yes, go to step 18 . If no, go to «DIAGNOSTIC AIDS»(ref-152429-S06840761612003021400000) .
18. Use scan tool to clear DTCs. Operate vehicle within freeze frame conditions that set the DTC. Monitor MISFIRE CURRENT CYL NO. data parameters on scan tool. Did a DTC set or did scan tool indicate a misfire in any cylinder? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Check for any of the following conditions

1. If any DTCs other than misfire (P0300 to P0304) are present, diagnose those DTCs first.
2. An intermittent ignition system malfunction may cause DTC P0301-P0304 to set. Check ignition system performance with an engine oscilloscope.
3. The scan tool data parameters ENGINE SPEED AT MISFIRE and LOAD AT MISFIRE are fixed at the time MIL illuminates. These scan tool displays can be used like additional lines of freeze frame data. Review information located in ENGINE SPEED AT MISFIRE and LOAD AT MISFIRE scan tool parameters. Information can help determine engine operation when misfire occurred.
4. Review misfire counters located in ENGINE DATA list of scan tool, while engine is running. If TOTAL MISFIRE CURRENT data parameter is increasing, misfire condition is present. Misfire activity can be monitored using scan tool in MISFIRE CURRENT CYL NO. data list parameter of appropriate cylinder. Use this information to determine if fault is present or an intermittent malfunction.
5. An intermittent can also be the result of a defective CKP sensor signal rotor. Remove CKP sensor and check the signal rotor through the sensor hole. Check condition of signal rotor for nicks, dents, missing teeth, and foreign material.
6. Check for engine overheating.
7. A Mass Air Flow (MAF) sensor output that is incorrect may cause PCM to command fuel system to go lean. Check performance of MAF sensor. If Heated Oxygen Sensor (HO2S) voltage is fixed low, while fuel trim is constantly high, check MAF sensor signal circuit for resistance. High circuit resistance can cause sensor to read a lower volume of air than actual, resulting in a lean fueling condition that can cause engine misfire.

An intermittent malfunction may be caused by a fault in the electrical circuits of ignition system or fuel system of misfiring cylinder. Check wiring harness and components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Repair any electrical circuit faults that were found. Information included in freeze frame data can be useful in determining vehicle operating conditions when DTC first set.

1. First condition: Engine running.
2. Second condition: Vehicle Speed Sensor (VSS) and Throttle Position (TP) sensor indicate vehicle is accelerating with engine speed more than 2000 RPM.

1. First condition: There is no bias voltage detected on KS signal circuit.
2. Second condition: No change is detected in KS signal for more than 20 seconds.

1. PCM illuminates the Malfunction Indicator Light (MIL).
2. PCM stores conditions that were present when DTC set as freeze frame data.
3. PCM enters FAIL-SAFE FUNCTION and defaults to maximum spark retard values.

1. PCM turns OFF MIL on the third consecutive trip cycle during which diagnostic has been run and fault condition is no longer present.
2. DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Are DTCs P0335 and P0340 both set? If yes, go to step 10 . If no, go to next step.
3. Does vehicle start and run? If yes, go to next step. If no, go to step 5 .
4. Connect scan tool. Turn ignition switch to RUN position, engine OFF. Save DTC and freeze frame information into scan tool memory. Use scan tool to clear DTCs. Operate vehicle within freeze frame conditions as specified. Is DTC P0335 set? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(ref-152429-S21671289962003021400000) .
5. Turn ignition OFF. Disconnect CKP sensor 2-pin harness connector. Measure resistance of CKP sensor using a DMM. Is resistance 1630-2740 ohms at 14-122°F (-10 to 50°C) or 2065-3225 ohms at 122-212°F (50-100°C)? If yes, go to next step. If no, go to step 13 .
6. Connect CKP sensor harness connector. Disconnect PCM White 34-pin harness connector C1. Connect DMM to CKP Input circuit and sensor ground circuit on harness side of PCM connector. Observe AC voltage while cranking engine. Was AC voltage indicated while cranking 1.4-1.6 volts AC? If yes, go to 14 . If no, go to next step.
7. Connect DMM to CKP Input circuit and a known-good ground. Observe AC voltage while cranking engine. Was AC voltage indicated, while cranking, 1.4-1.6 volts AC? If yes, go to 9 . If no, go to step 11 .
8. Check for an open or a short in CKP sensor input circuit. Did you find and repair a condition? If yes, go to step 15 . If no, go to go to step 11 .
9. Repair open in CKP sensor ground circuit. After repair, go to step 15 .
10. Check for an open in CKP and CMP sensor ground circuit between splice SP108 and PCM. Repair as necessary. Did you find and correct a condition? If yes, go to step 15 . If no, go to step 14 .
11. Remove CKP sensor. Visually check CKP sensor signal rotor for the following conditions: Any damaged teeth. Any foreign material. Correct installation. Repair as necessary. Did you find and correct a condition? If yes, go to step 15 . If no, go to next step.
12. Check for an intermittent or a poor electrical connection at CKP sensor. Repair as necessary. Did you find and correct a condition? If yes, go to step 15 . If no, go to next step.
13. Replace CKP sensor. After repair, go to step 15 .
14. Replace PCM. After repair, go to step 15 .
15. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S04381864872003020400000) as specified. Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
16. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Check for the following conditions

1. A loose KS can cause a loss of KS signal. Check KS for proper torque. Correct KS sensor torque is 29 ft. lbs (39 N.m).
2. Engine acceleration will be compromised and AT downshifts delayed when operating in FAIL-SAFE mode.
3. If DTC P0325 sets while engine is idling, check for a loose connection at PCM or KS.

An intermittent malfunction may be caused by a fault in the KS sensor electrical circuit. Check wiring harness and components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Information included in freeze frame data can be useful in determining vehicle operating conditions present when DTC first set.

The crank signal circuit, PCM connector C2 terminal No. 9, must be pulled high for diagnostic to run when starting engine.

1. No Crankshaft Position Sensor signal to PCM for 5 seconds while cranking engine.
2. No Crankshaft Position Sensor signal to PCM with engine speed at 600 RPM or more.

1. PCM illuminates Malfunction Indicator Light (MIL) during the second key cycle in which the DTC sets.
2. PCM stores conditions which were present when DTC set as freeze frame data.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. A DTC will clear after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Are DTCs P0335 and P0340 both set? If yes, go to step 10 . If no, go to next step.
3. Does vehicle start and run? If yes, go to next step. If no, go to step 5 .
4. Install a scan tool. Turn ignition switch to RUN position, engine OFF. Save DTC and freeze frame information into scan tool memory. Use scan tool to clear DTCs. Operate vehicle within freeze frame conditions as specified. Is DTC P0335 set? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(ref-152429-S31918633962003020400000) .
5. Turn ignition OFF. Disconnect CKP sensor 2-pin harness connector. Measure resistance of CKP sensor with a DMM. Is resistance 630-2740 ohms at 14-122°F (-10 to 50°C) or 2065-3225 ohms at 122-212°F (50-100°C)? If yes, go to next step. If no, go to step 13 .
6. Connect CKP sensor harness connector. Disconnect PCM White 34-pin harness connector C1. Connect DMM to CKP Input circuit and sensor ground circuit on harness side of PCM connector. Observe AC voltage while cranking engine. Was AC voltage indicated while cranking 1.4-1.6 volts AC? If yes, go to step 14 . If no, go to next step.
7. Connect DMM to CKP Input circuit and a known-good ground. Observe AC voltage while cranking engine. Was AC voltage indicated while cranking 1.4-1.6 volts AC? If yes, go to step 9 . If no, go to next step.
8. Check for an open or a short in CKP sensor input circuit. Did you find and repair a condition? If yes, go to step 15 . If no, go to step 11 .
9. Repair open in CKP sensor ground circuit. After repairs, go to step 15 .
10. Check for an open in CKP and CMP sensor ground circuit between splice SP108 and PCM. Repair as necessary. Did you find and correct a condition? If yes, go to step 15 . If no, go to step 14 .
11. Remove CKP sensor. Visually Check CKP sensor signal rotor for the following conditions: Any damaged teeth. Any foreign material. Correct installation. Repair as necessary. Did you find and correct a condition? If yes, go to step 15 . If no, go to next step.
12. Check for an intermittent or a poor electrical connection at CKP sensor. Repair as necessary. Did you find and correct a condition? If yes, go to step 15 . If no, go to next step.
13. Replace CKP sensor. After repair, go to step 15 .
14. Replace PCM. After repair, go to next step.
15. Use scan tool to clear the DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S00469621032003020400000) as specified. Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
16. With a scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Check for any of the following conditions

1. Check Crankshaft Position (CKP) sensor output signal with a scan tool. The scan tool will display engine speed while cranking when PCM detects CKP sensor signal. Observe ENGINE SPEED parameter while cranking engine. Scan tool should indicate a steady 200-300 RPM while cranking.
2. CKP sensor performance may be affected by temperature. Check sensor operation and internal resistance at various temperatures. CKP sensor resistance when cold should be 1630-2740 ohms at 14-122°F (-10 to 50°C). CKP sensor resistance when hot should be 2065-3225 ohms at 122-212°F (50-100°C).
3. An intermittent DTC P0335 can be caused by a defective signal rotor. Remove CKP sensor and visually check the teeth of the signal rotor through CKP sensor aperture for damage, foreign material, or incorrect installation.
4. A DTC P0335 that sets while driving and checks okay may be caused by inadequate CKP sensor circuit shielding. Check CKP sensor circuit is properly shielded and drain wire is fastened securely to ground.

An intermittent malfunction may be caused by a fault in the CKP sensor electrical circuit. Check the wiring harness and the components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Repair any electrical circuit faults found. Information included in freeze frame data can be useful in determining vehicle operating conditions when the DTC first set.

Engine is running.

1. No CMP sensor signal is sent to PCM while cranking.
2. No CMP sensor signal is sent to PCM with engine speed at 600 RPM or more.

1. PCM illuminates Malfunction Indicator Light (MIL).
2. PCM stores conditions which were present when DTC set as freeze frame data.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Does vehicle not start or almost start and then stall immediately? If yes, go to step 10 . If no, go to next step.
3. Does vehicle start and run with MIL illuminated and DTC P0340 set? If yes, go to step 5 . If no, go to next step.
4. Install scan tool. Turn ignition switch to RUN position, engine OFF. Save DTC and freeze frame information. Use scan tool to clear DTCs. Operate vehicle within freeze frame conditions as specified. Did DTC P0340 set? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(ref-152429-S10858407892003020400000) .
5. Turn ignition OFF. Disconnect CMP sensor 2-pin harness connector. Measure resistance of CMP sensor with a DMM. Is resistance 835-1400 ohms at 14-122°F (-10 to 50°C) or 1060-1645 ohms at 122-212°F (50-100°C)? If yes, go to next step. If no, go to step 13 .
6. Connect scan tool. Connect DVOM across CMP sensor terminals. Select AC voltage on DVOM. Start engine. Observe AC voltage on the DMM while checking engine speed on scan tool. See «TEST DESCRIPTION»(ref-152429-S31723427642003020400000) . Was AC voltage indicated approximately twice the engine speed? If yes, go to next step. If no, go to step 12 .
7. Probe ground circuit of CMP sensor on harness side with a test light connected to battery voltage. Does test light illuminate? If yes, go to next step. If no, go to step 11 .
8. Disconnect PCM White 34-pin harness connector C1. Remove CMP input wire from PCM harness connector C1. Reconnect harness connector C1 to PCM, leaving CMP input wire free to be tested. Connect DMM to CMP input wire and ground. Start engine. Observe AC voltage on DMM while observing engine speed on the scan tool. Is AC voltage indicated approximately twice the engine speed? If yes, go to step 14 . If no, go to next step.
9. Repair open or short in CMP input circuit. After repair, go to step 15 .
10. Check for an open in the CMP and CKP sensor ground circuit between splice SP108 and PCM. Repair as necessary. Did you find and correct a condition? If yes, go to step 15 . If no, go to step 14 .
11. Repair open in the CMP sensor ground circuit between the sensor and splice SP108. After repair, go to step 15 .
12. Remove CMP sensor. Visually check CMP sensor signal rotor for the following conditions: A missing or damaged tooth. Any foreign material. Correct installation. Repair as necessary. Did you find and correct a condition? If yes, go to step 15 . If no, go to next step.
13. Replace CMP sensor. After repair, go to step 15 .
14. Replace PCM. After repair, go to step 15 .
15. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S17781830282003021700000) as specified. Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
16. Using scan tool, observe stored information, CAPTURE INFO. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no other DTCs are displayed, system is okay at this time.

Check for any of the following conditions

1. Camshaft Position (CMP) sensor output may be affected by temperature. Check sensor operation and internal resistance at various temperatures. CMP sensor resistance when cold should be 835-1400 ohms at 14-122°F (-10 to 50°C). CMP sensor resistance when hot should be 1060-1645 ohms at 122-212°F (50-100°C).
2. CMP sensor performance can be checked with a DMM and a scan tool. AC voltage output of CMP sensor, as measured with a DMM across sensor electrical terminals, is approximately the same as engine speed. Run engine at several different engine speeds and compare numerical value on scan tool with numerical voltage reading on DMM. If the reading of DMM and scan tool are not nearly equal, check for a faulty sensor or signal rotor.
3. A DTC P0340 that sets while driving and checks OK may be caused by inadequate CMP sensor circuit shielding. Verify CMP sensor circuit is properly shielded and drain wire is fastened securely to ground.

An intermittent malfunction may be caused by a fault in CMP sensor electrical circuit. Check wiring harness and components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Repair any electrical circuit faults that were found. Information included in freeze frame data can be useful in determining vehicle operating conditions when DTC first set.

1. Engine coolant temperature is more than 158°F (70°C).
2. Engine speed is 2500-3000 RPM for at least 3 minutes while driving at certain vehicle speeds.
3. Engine is operating in Closed Loop.

HO2S 2 signal is as active as HO2S 1 signal.

1. PCM illuminates Malfunction Indicator Light (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with fault active.
2. PCM stores conditions which were present when DTC set as freeze frame data.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Check any for any HO2S DTCs and diagnose those DTCs first. Are DTCs P0130, P0133, P0135, P0136, or P0141 set? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, go to next step.
3. Install scan tool. Start engine. Run engine until normal operating temperature is reached. Verify the engine is operating in closed loop. Run engine at 2500-3000 RPM for 3 minutes. Monitor HO2S 1 and HO2S 2 signals on scan tool. Is HO2S 2 signal as active as HO2S 1 signal? If yes, go to step 5 . If no, go to next step.
4. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S36888963242003020400000) or until catalyst test is complete. Did a DTC P0420 set? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(ref-152429-S37309687862003020400000) .
5. Visually and physically check the 3-way catalytic converter for the following concerns: Any dents. A severe discoloration caused by excessive temperatures. Any holes. An internal rattle caused by a damaged catalyst. Ensure the 3-way catalytic converter is a high quality part and meets OEM specifications. Was a problem found? If yes, go to step 8 . If no, go to next step.
6. Visually and physically check exhaust system for leaks, damaged, loose or missing hardware. Repair as necessary. Was a repair necessary? If yes, go to step 9 . If no, go to next step.
7. Visually and physically check HO2S 2 for the following conditions: The pigtail and the wiring harness making contact with the exhaust pipe. A loose HO2S 2. Any road damage. Repair as necessary. Was a repair necessary? If yes, go to step 9 . If no, go to next step.
8. Replace 3-way catalytic converter. After repair, go to step 10 .
9. Start engine. Run engine until normal operating temperature is reached. Verify engine is operating in closed loop. Run engine at 2500-3000 RPM for 3 minutes. Monitor HO2S 1 and HO2S 2 signals on scan tool. Is HO2S 2 signal as active, as HO2S 1 signal? If yes, go to «DIAGNOSTIC AIDS»(ref-152429-S37309687862003020400000) . If no, go to next step.
10. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S36888963242003020400000) or until catalyst test is complete. Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
11. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Check for any of the following conditions

1. A contaminated or malfunctioning HO2S can cause inaccurate sensor readings. For checks of HO2S, see «DIAGNOSTIC AIDS»(ref-152429-S29076729212003021300000) in DTC P0130.
2. Observe HO2S 1 voltage and fuel trim readings with a scan tool. If HO2S 1 voltage is fixed low, while fuel trim is constantly high, check Mass Air Flow (MAF) sensor signal circuit for resistance. High circuit resistance can cause sensor to read a lower volume of air than actual, resulting in a lean fueling condition. This lean fueling condition can cause HO2S 2 voltage to be fixed low, causing DTC P0420 diagnostic to fail.
3. A damaged HO2S wiring harness. Check HO2S wiring harnesses for damage and repair as necessary.
4. If a DTC P0420 is intermittent, driving vehicle under conditions outlined in Inspection/Maintenance (I/M) section can verify whether fault is present. See «INSPECTION/MAINTENANCE CATALYST SYSTEM SET PROCEDURE»(ref-152429-S30545018472003020400000) under INSPECTION/MAINTENANCE PROCEDURES.
5. After returning to an idle, the HO2S 1 signal may stay rich or lean for several seconds, causing the test to be delayed.

A catalytic converter failure may be caused by any of the following conditions

1. An engine misfire.
2. An inadequate secondary ignition voltage.
3. Any excessive engine oil or engine coolant consumption.
4. A rich engine fueling.

An intermittent malfunction may be caused by faults in HO2S electrical circuits. Check wiring harness and components for an intermittent condition. See

INTERMITTENTS

in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. The information included in freeze frame data can be useful in determining vehicle operating conditions when DTC first set.

1. Barometric (BARO) pressure is more than 75 kPa.
2. Fuel level is 25-75 percent.
3. ECT sensor and Intake Air Temperature (IAT) sensor are near the same temperature at engine start.
4. ECT sensor is at least 165°F (74°C) after engine warm up.
5. Vehicle has been driven for at least 20 minutes.
6. EVAP canister purge solenoid has been open and Fuel Tank Pressure (FTP) sensor indicates a negative pressure in the fuel tank.

EVAP system is not able to achieve or maintain the expected vacuum pressure during the diagnostic test.

1. PCM illuminates Malfunction Indicator Light (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with fault active.
2. PCM records operating conditions at the time the diagnostic fails. This information is stored in freeze frame buffer.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. A DTC will clear after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Check for DTCs. Is a DTC P0450 or P0451 present? If yes, go to «DTC P0450: FUEL TANK PRESSURE SENSOR CIRCUIT»(ref-152429-S09432474572003020400000) and «DTC P0451: FUEL TANK PRESSURE SENSOR PERFORMANCE»(ref-152429-S41829319122003020400000). If no, go to next step.
3. Review freeze frame/failure records. Diagnose DTC captured in freeze frame/failure records first. Is DTC P0440 captured in freeze frame/failure records? If yes, go to next step. If no, go to step «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000).
4. Check EVAP system for the following conditions: A loose, missing, or damaged service port Schrader valve. A loose, incorrect, missing, or damaged fuel fill cap. A damaged EVAP purge solenoid. Raise and support vehicle on a hoist. Check EVAP system for the following conditions: Any disconnected, improperly routed, kinked, or damaged EVAP pipes and hoses. A damaged EVAP vent solenoid or EVAP canister. Did you find and correct the condition? If yes, go to step 44. If no, go to next step.
5. Command EVAP purge solenoid ON and OFF using scan tool. Do you hear or feel a click as EVAP purge solenoid is commanded ON and OFF? If yes, go to next step. If no, go to step 8.
6. Command EVAP vent solenoid ON and OFF using scan tool. Do you hear or feel a click as EVAP vent solenoid is commanded ON and OFF? If yes, go to next step. If no, go to step 10.
7. Command EVAP pressure switching solenoid ON and OFF using scan tool. Do you hear or feel a click as EVAP pressure switching solenoid is commanded ON and OFF? If yes, go to step 14. If no, go to step 12.
8. Disconnect EVAP purge solenoid. Turn ignition switch to RUN position, engine OFF. Connect test light between ignition positive voltage circuit of EVAP purge solenoid and a known-good ground. Does test light illuminate? If yes, go to next step. If no, go to step 35.
9. Connect a test light between ignition positive voltage circuit of EVAP purge solenoid and control circuit of EVAP purge solenoid. Command EVAP purge solenoid ON using scan tool. Does the test light illuminate when EVAP purge solenoid is commanded ON and turn OFF when EVAP purge solenoid is commanded OFF? If yes, go to step 27. If no, go to step 24.
10. Turn ignition switch to RUN position, engine OFF. Disconnect EVAP vent solenoid. Connect a test light between EVAP vent solenoid ignition positive voltage circuit and a known-good ground. Does the test light illuminate? If yes, go to next step. If no, go to step 35.
11. Connect a test light between EVAP vent solenoid ignition positive voltage circuit and control circuit of EVAP vent solenoid. Using scan tool, command EVAP vent solenoid ON. Does test light illuminate when EVAP vent solenoid is commanded ON and turn OFF when EVAP vent solenoid is commanded OFF? If yes, go to step 28. If no, go to step 25.
12. Turn ignition switch to RUN position, engine OFF. Disconnect EVAP pressure switching solenoid. Connect test light between EVAP pressure switching solenoid ignition positive voltage circuit and a known-good ground. Does test light illuminate? If yes, go to next step. If no, go to step 35.
13. Connect test light between EVAP pressure switching solenoid ignition positive voltage circuit and EVAP pressure switching solenoid control circuit. Using scan tool, command EVAP pressure switching solenoid ON. Does test light illuminate when EVAP pressure switching solenoid is commanded ON and turn OFF when EVAP pressure switching solenoid is commanded OFF? If yes, go to step 29. If no, go to step 26.
14. Connect nitrogen/smoke supply hose of Evaporative Emission System Tester (EEST - J 41413-200), or equivalent, to EVAP service port. Turn nitrogen/smoke valve on control panel to SMOKE. Use remote switch to introduce smoke into EVAP system. Continue to introduce smoke until a steady flow of smoke is seen exiting the EVAP canister drain hose. (Scheme 56) Plug EVAP canister drain hose using Plug (J 41413-301), or equivalent. Turn nitrogen/smoke valve on control panel to NITROGEN. Use remote switch to introduce Nitrogen gas into EVAP system for 60 seconds. Check entire EVAP system for exiting smoke with High Intensity White Light (J 41413-SPT), or equivalent. Continue to introduce smoke, then Nitrogen, at 60 second intervals, until source of leak has been located. Did you locate and repair a leak source? If yes, go to step 44. If no, go to next step.
15. Remove fuel fill cap. Observe FTP sensor using scan tool. Is FTP sensor near 0.09 in. H2O? If yes, go to next step. If no, go to step 30.
16. Install fuel fill cap on fuel fill pipe. Turn EEST nitrogen/smoke valve on control panel to NITROGEN. Use EEST to pressurize EVAP system to 13 in. H2O. Is the FUEL TANK PRESSURE SENSOR parameter more than 5 in. H2O? If yes, go to next step. If no, go to step 19.
17. Use remote switch to stop introducing nitrogen into EVAP system. Command EVAP purge solenoid ON. Is FTP sensor parameter less than one in. H2O? If yes, go to step 21. If no, go to next step.
18. Disconnect EVAP purge vacuum source from EVAP purge solenoid. Is FTP Sensor parameter less than one in. H2O? If yes, go to step 34. If no, go to step 39.
19. Disconnect EVAP canister vapor line. Does EEST gauge indicate zero in. H2O? If yes, go to step 36. If no, go to next step.
20. Disconnect EVAP canister purge line. Does EEST gauge indicate zero in. H2O? If yes, go to step 23. If no, go to step 37.
21. Disconnect EVAP solenoid vent hose at EVAP canister. Command EVAP vent solenoid ON (closed). Install a vacuum pump to vent hose, and apply a vacuum. Did you achieve a vacuum? If yes, go to next step. If no, go to step 32.
22. Command EVAP vent solenoid OFF (open). Does vacuum decrease? If yes, go to next step. If no, go to step 33.
23. Check for a faulty EVAP canister. See «EVAPORATIVE EMISSION CONTROL SYSTEM DIAGNOSIS»(ref-152779-S17488005022003022500000) under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 1.8L VIBE article. Did you replace EVAP canister? If yes, go to step 44. If no, go to step 38.
24. Check EVAP purge solenoid control circuit for an open, short to ground, or short to voltage. Did you find and correct the condition? If yes, go to step 44. If no, go to step 38.
25. Check EVAP purge solenoid control circuit for an open, short to ground, or short to voltage. Did you find and correct the condition? If yes, go to step 44. If no, go to step 31.
26. Check EVAP pressure switching solenoid control circuit for an open, short to ground or short to voltage. Did you find and correct the condition? If yes, go to step 44. If no, go to step 31.
27. Check EVAP canister purge solenoid for an intermittent and for a poor connection. Did you find and correct the condition? If yes, go to step 44. If no, go to step 39.
28. Check EVAP vent solenoid for an intermittent and for a poor connection. Did you find and correct the condition? If yes, go to step 44. If no, go to step 40.
29. Check EVAP pressure switching solenoid for an intermittent and for a poor connection. Did you find and correct the condition? If yes, go to step 44. If no, go to step 41.
30. Check FTP sensor for an intermittent and for a poor connection. Did you find and correct the condition? If yes, go to step 44. If no, go to step 42.
31. Check PCM for an intermittent and for a poor connection. Did you find and correct the condition? If yes, go to step 44. If no, go to step 43.
32. Check for a leak source in EVAP solenoid vent hose. Repair as necessary. Did you find and correct the condition? If yes, go to step 44. If no, go to step 40.
33. Check for a pinched or obstructed EVAP vent hose. Repair as necessary. Did you find and correct the condition? If yes, go to step 44. If no, go to step 40.
34. Repair pinched or obstructed EVAP purge solenoid vacuum source. After repair, go to step 44.
35. Repair open or short to ground in EVAP solenoid ignition positive voltage circuit. Replace fuse as necessary. After repair, go to step 44.
36. Repair restriction in EVAP vapor pipe. After repair, go to step 44.
37. Repair restriction in EVAP purge pipe. After repair, go to step 44.
38. Was a DTC P0446 also set? If yes, go to «DTC P0446: EVAP VENT SYSTEM PERFORMANCE»(ref-152429-S30489705412003020400000). If no, go to «DIAGNOSTIC AIDS»(ref-152429-S21995557672003020400000)
39. Replace EVAP purge solenoid. After repair, go to step 44.
40. Replace EVAP vent solenoid. After repair, go to step 44.
41. Replace pressure switching solenoid. After repair, go to step 44.
42. Replace FTP sensor. After repair, go to step 44.
43. Replace PCM. After repair, go to next step.
44. Connect nitrogen/smoke supply hose of EEST to EVAP service port. Plug EVAP canister drain hose using Plug (J 41413-301), or equivalent. (Scheme 56) Turn nitrogen/smoke valve to NITROGEN. Pressurize EVAP system to 5 in. H2O. Observe EEST pressure/vacuum gauge for 5 minutes. Does pressure/vacuum gauge remain constant? If yes, go to next step. If no, go to step 14.
45. Using scan tool, observe CAPTURE INFO. Are there any DTCs that have not been diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000). If no, system is okay at this time.

Scheme 56

1. To help locate intermittent leaks, use Evaporative Emissions System Tester (EEST - J 41413-200), or equivalent, to introduce smoke into EVAP system. Move all EVAP components while observing smoke with High Intensity White Light (J 41413-SPT), or equivalent.
2. To improve the visibility of smoke exiting the EVAP system, observe the suspected leak area from different angles using the High Intensity White Light.
3. A temporary blockage in EVAP purge solenoid, purge pipe or EVAP canister could cause an intermittent condition. Check and repair any restriction in EVAP system.
4. Operating vehicle in CHECK MODE will increase the ability of the PCM to detect engine control system malfunctions. See «SERVICE BAY TESTS»(ref-152429-S19809249722003021000000) under SELF-DIAGNOSTIC SYSTEM.
5. For intermittent conditions, see «INTERMITTENTS»(ref-153013-S39990244982003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.
6. If the DTC cannot be duplicated, information included in freeze frame data can be useful in determining vehicle operating conditions when DTC was first set.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. A DTC will clear after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool and check for DTCs. Is a DTC P0450 or P0451 present? If yes, go to «DTC P0450: FUEL TANK PRESSURE SENSOR CIRCUIT»(ref-152429-S09432474572003020400000) or «DTC P0451: FUEL TANK PRESSURE SENSOR PERFORMANCE»(ref-152429-S41829319122003020400000) . If no, go to next step.
3. Review freeze frame/failure records. Diagnose DTC captured in freeze frame/failure records first. Is DTC P0441 captured in freeze frame/failure records? If yes, go to next step. If no, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) .
4. Using scan tool, command EVAP purge solenoid ON and OFF. Do you hear or feel a click as EVAP purge solenoid is commanded ON and OFF? If yes, go to next step. If no, go to step 10 .
5. Remove purge line from EVAP purge solenoid. Connect a vacuum gauge to EVAP purge solenoid purge port. Start engine. Does vacuum gauge indicate a vacuum being applied? If yes, go to step 18 . If no, go to next step.
6. With engine running, command purge valve ON (open). Does vacuum gauge indicate a vacuum being applied? If yes, go to next step. If no, go to step 17 .
7. Reinstall EVAP purge line to purge solenoid. Remove fuel fill cap to release any pressure inside fuel tank. Reinstall fuel fill cap. Turn ignition switch to RUN position, engine OFF. Observe FTP sensor parameter on scan tool. Is FTP sensor 0.0-0.5 in. H2O? If yes, go to next step. If no, go to step 15 .
8. Start engine. Select EVAP PURGE/SEAL function on scan tool. See «SERVICE BAY TESTS»(ref-152429-S19809249722003021000000) under SELF-DIAGNOSTIC SYSTEM. Command EVAP Purge/Seal function ON. Does FTP sensor indicate a reading of -12.50 in. H2O for as long as 2 minutes?
9. Repeat EVAP Purge/Seal test exactly as detailed below. Command EVAP PURGE/SEAL function ON. Monitor FTP sensor with scan tool for -12.50 in. H2O for the duration of the test. Continue to observe FTP sensor for 30 seconds after PURGE/SEAL test is complete. Did FTP sensor indicate that vacuum dropped to less than -10.00 in. H2O in the 30 seconds after the test was complete? IF yes, go to «DIAGNOSTIC AIDS»(ref-152429-S15276437052003021800000) . If no go to «DTC P0446: EVAP VENT SYSTEM PERFORMANCE»(ref-152429-S30489705412003020400000) .
10. Disconnect EVAP purge solenoid. Turn ignition switch to RUN position, engine OFF. Connect test light between EVAP purge solenoid ignition positive voltage circuit and a known-good ground. Does test light illuminate? If yes, go to next step. If no, go to step 13 .
11. Connect test light between EVAP purge solenoid ignition positive voltage circuit and EVAP purge solenoid control circuit. Using scan tool, command EVAP purge solenoid ON. Does test light illuminate when EVAP purge solenoid is commanded ON, and turn OFF when EVAP purge solenoid is commanded OFF? If yes, go to step 14 . If no, go to next step.
12. Check EVAP purge solenoid control circuit for an open, short to voltage, or short to ground. Did you find and correct the condition? If yes, go to step 21 . If no, go to step 16 .
13. Repair open or short to ground in EVAP purge solenoid ignition positive voltage circuit. Replace fuse as necessary. After repair, go to step 21 .
14. Check EVAP canister purge solenoid for an intermittent and for a poor connection. Repair as necessary. After repair, go to step 21 .
15. Check FTP sensor for an intermittent and for a poor connection. Did you find and correct the condition? If yes, go to step 21 . If no, go to step 19 .
16. Check PCM connectors for an intermittent and for a poor connection. Did you find and correct the condition? If yes, go to step 21 . If no, go to step 20 .
17. Check EVAP purge solenoid vacuum supply for a blockage or restriction. Did you find and correct the problem? If yes, go to step 21 . If no, go to next step.
18. Replace EVAP purge solenoid. After repair, go to step 21 .
19. Replace FTP sensor. After repair, go to step 21 .
20. Replace PCM. After repair, go to next step.
21. Start engine. Select EVAP PURGE/SEAL function on scan tool. See «SERVICE BAY TESTS»(ref-152429-S19809249722003021000000) under SELF-DIAGNOSTIC SYSTEM. Command EVAP PURGE/SEAL function ON. Does FTP sensor indicate a reading of -12.50 in. H2O for as long as 2 minutes? If yes, go to step 23 . If no, go to next step.
22. The EVAP System failed EVAP PURGE/SEAL test. Is there an EVAP system DTC that has not been diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, go to step 4 .
23. Observe the CAPTURE INFO using scan tool. Are there any DTCs that have not been diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

1. If DTC P0441 is the only EVAP DTC set, the most likely cause is an inoperable EVAP canister purge valve. Check EVAP canister purge valve carefully for faulty connections and erratic operation.
2. An intermittent malfunction may be caused by a fault in any of EVAP solenoid electrical circuits. Check wiring harness and components for an intermittent condition. See «INTERMITTENTS»(ref-153013-S39990244982003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.
3. If the DTC cannot be duplicated, information included in freeze frame data can be useful in determining vehicle operating conditions when DTC was first set.
4. Operating vehicle in CHECK MODE will increase the ability of the PCM module to detect engine control system malfunctions. See «SERVICE BAY TESTS»(ref-152429-S19809249722003021000000) under SELF-DIAGNOSTIC SYSTEM.

1. Barometric (BARO) pressure is more than 75 kPa.
2. Fuel level is 25-75 percent.
3. ECT and Intake Air Temperature (IAT) sensors are near the same temperature at engine start.
4. ECT sensor is at least 165°F (74°C) after engine warm up.
5. Vehicle has been driven for at least 20 minutes.
6. EVAP canister purge valve has been open and Fuel Tank Pressure (FTP) sensor indicates a negative pressure in the fuel tank.

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

1. PCM illuminates Malfunction Indicator Light (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with fault active.
2. PCM records operating conditions at the time the diagnostic fails. This information is stored in the freeze frame buffer.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. A DTC will clear after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool. Check for DTCs. Is a DTC P0450 or P0451 present? If yes, see «DTC P0450: FUEL TANK PRESSURE SENSOR CIRCUIT»(ref-152429-S09432474572003020400000) or «DTC P0451: FUEL TANK PRESSURE SENSOR PERFORMANCE»(ref-152429-S41829319122003020400000). If no, go to next step.
3. Review freeze frame/failure records. Diagnose DTC captured in freeze frame/failure records first. Is DTC P0442 captured in freeze frame/failure records? If yes, go to next step. If no, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000).
4. Check EVAP system for the following conditions: A loose, missing, or damaged service port Schrader valve. A loose, incorrect, missing, or damaged fuel fill cap. A damaged EVAP purge solenoid. Raise and support vehicle on a hoist. Check EVAP system for the following conditions: Any disconnected, improperly routed, kinked, or damaged EVAP pipes and hoses. A damaged EVAP vent solenoid or EVAP canister. Did you find and correct the condition? If yes, go to step 10. If no, go to next step.
5. Connect the nitrogen/smoke supply hose of Evaporative Emission System Tester (EEST - J 41413-200), or equivalent, to EVAP service port. Turn nitrogen/smoke valve on the control panel to SMOKE. Use remote switch to introduce smoke into EVAP system. Continue to introduce smoke until a steady flow of smoke is seen exiting EVAP canister drain hose. (Scheme 56) Plug EVAP canister drain hose using Plug (J 41413-301), or equivalent. Turn nitrogen/smoke valve on control panel to NITROGEN. Use remote switch to introduce Nitrogen gas into EVAP system for 60 seconds. Check entire EVAP system for exiting smoke with a High Intensity White Light (J 41413-SPT), or equivalent. Continue to introduce smoke, then Nitrogen, at 60 second intervals, until the source of the leak has been located. Did you locate and repair a leak source? If yes, go to step 10. If no, go to next step.
6. Remove fuel fill cap. Observe FTP in. H20 using scan tool. Is the FTP in. H20 near 0.09 in. H2O? If yes, go to next step. If no, go to step 9.
7. Install fuel fill cap on fuel fill pipe. Turn nitrogen/smoke valve on EEST control panel to NITROGEN. Use EEST to pressurize EVAP system to 10 in. H2O. Is the FTP parameter more than 5 in. H2O? If yes, go to next step. If no, go to step 9.
8. Use remote switch to stop introducing nitrogen into EVAP system. Command EVAP purge solenoid ON. Is the FTP sensor parameter less than one in. H2O? If yes, go to «DIAGNOSTIC AIDS»(ref-152429-S08351843132003020400000). If no, go to next step.
9. Replace FTP sensor. After repair, go to next step.
10. Connect the nitrogen/smoke supply hose of EEST (J 41413-200), or equivalent, to EVAP service port. Plug EVAP canister drain hose using Plug (J 41413-301), or equivalent. (Scheme 56) Turn nitrogen/smoke valve to NITROGEN. Pressurize EVAP system to 5 in. H2O. Observe EEST pressure/vacuum gauge for 5 minutes. Does pressure/vacuum gauge remain constant? If yes, go to next step. If no, go to step 5.
11. Observe CAPTURE INFO using scan tool. Are there any DTCs that have not been diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000). If no, system is okay at this time.

1. EVAP control system is required to detect evaporative emission fuel system leaks as small as 0.020 in. Hg, between fuel fill cap and purge solenoid.
2. To help locate intermittent leaks, use the Evaporative Emissions System Tester (EEST - J 41413-200), or equivalent, to introduce smoke into EVAP system. Move all EVAP components while observing smoke with the High Intensity White Light (J 41413-SPT), or equivalent.
3. A temporary blockage in EVAP purge solenoid, purge pipe or EVAP canister could cause an intermittent condition. Check and repair any restriction in EVAP system.
4. To improve visibility of smoke exiting the EVAP system, observe suspected leak area from different angles with the High Intensity White Light.
5. Reviewing freeze frame records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.
6. For intermittent conditions refer to Intermittent Conditions. See «INTERMITTENTS»(ref-153013-S39990244982003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.

1. Barometric (BARO) pressure is more than 75 kPa.
2. Fuel level is 25-75 percent.
3. Engine Coolant Temperature (ECT) and Intake Air Temperature (IAT) sensor are near the same temperature at engine start.
4. ECT sensor is at least 165°F (74°C) after engine warm up.

1. Pressure indicated in EVAP canister and fuel tank does not drop when EVAP canister purge valve is ON.
2. Pressure indicated in EVAP canister remains very low when compared to atmospheric pressure when EVAP canister purge solenoid valve is OFF.

1. PCM illuminates Malfunction Indicator Light (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with fault active.
2. PCM records operating conditions at the time the diagnostic fails. This information is stored in freeze frame buffer.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. A DTC will clear after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Install scan tool and check for DTCs. Is a DTC P0450 or P0451 present? If yes, go to «DTC P0450: FUEL TANK PRESSURE SENSOR CIRCUIT»(ref-152429-S09432474572003020400000) or «DTC P0451: FUEL TANK PRESSURE SENSOR PERFORMANCE»(ref-152429-S41829319122003020400000) . If no, go to next step.
3. Review freeze frame/failure records. Diagnose DTC captured in freeze frame/failure records first. Is DTC P0446 captured in freeze frame/failure records? If yes, go to next step. If no, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) .
4. Using scan tool, command EVAP vent solenoid ON and OFF. Do you hear or feel a click as EVAP vent solenoid is commanded ON and OFF? If yes, go to next step. If no, go to step 11 .
5. Using scan tool, command EVAP pressure switching solenoid ON and OFF. Do you hear or feel a click as EVAP pressure switching solenoid is commanded ON and OFF? If yes, go to next step. If no, go to step 13 .
6. Remove fuel fill cap to release any pressure inside fuel tank. Re-install fuel fill cap. Turn ignition switch to RUN position, engine OFF. Observe FTP sensor parameter on scan tool. Is FTP sensor 0.09 in. H2O? If yes, go to next step. If no, go to step 20 .
7. Disconnect EVAP solenoid vent hose at the EVAP canister. Command EVAP vent solenoid ON (closed). Install a vacuum pump to vent hose and apply a vacuum. Did you achieve a vacuum? If yes, go to next step. If no, go to step 22 .
8. Command EVAP vent solenoid OFF (open). If yes, go to next step. If no, go to step 23 .
9. Disconnect EVAP pressure switching solenoid hose from one of the ports. Command EVAP pressure switching solenoid OFF (closed). Install a vacuum pump to the solenoid port and apply a vacuum. Did you achieve a vacuum? If yes, go to next step. If no, go to step 25 .
10. Command EVAP pressure switching ON (open). Does the vacuum decrease? If yes, go to step 28 . If no, go to step 25 .
11. Turn ignition switch to RUN position, engine OFF. Disconnect EVAP vent solenoid. Connect a test light between EVAP vent solenoid ignition positive voltage circuit and a known-good ground. Does test light illuminate? If yes, go to next step. If no, go to step 17 .
12. Connect test light between EVAP vent solenoid ignition positive voltage circuit and control circuit. Using scan tool, command EVAP vent solenoid ON. Does test light illuminate when EVAP vent solenoid is commanded ON and turn OFF when EVAP vent solenoid is commanded OFF? If yes, go to step 18 . If no, go to step 15 .
13. Turn ignition switch to RUN position, engine OFF. Disconnect EVAP pressure switching solenoid. Connect test light between EVAP pressure switching solenoid ignition positive voltage circuit and a known-good ground. Does test light illuminate? If yes, go to next step. If no, go to step 17 .
14. Connect test light between EVAP pressure switching solenoid ignition positive voltage circuit and control circuit. Using scan tool, command EVAP pressure switching solenoid ON. Does test light illuminate when EVAP pressure switching solenoid is commanded ON and turn OFF when EVAP pressure switching solenoid is commanded OFF? If yes, go to step 19 . If no, go to step 16 .
15. Check EVAP vent solenoid control circuit for an open, short to ground, or a short to voltage. Did you find and correct the condition? If yes, go to step 28 . If no, go to step 21 .
16. Check EVAP pressure switching solenoid control circuit for an open, a short to ground, or for a short to voltage. Did you find and correct the condition? If yes, go to step 28 . If no, go to step 21 .
17. Repair open or short to ground in EVAP solenoid ignition positive voltage circuit. Replace fuse as necessary. After repair, go to step 28 .
18. Check EVAP canister vent solenoid for an intermittent and for a poor connection. Did you find and correct the condition? If yes, go to step 28 . If no, go to step 24 .
19. Check EVAP pressure switching solenoid for an intermittent and for a poor connection. Did you find and correct the condition? If yes, go to step 28 . If no, go to step 26 .
20. Check FTP sensor for an intermittent and for a poor connection. Did you find and correct the condition? If yes, go to step 28 . If no, go to step 26 .
21. Check PCM for an intermittent and for a poor connections. Did you find and correct the condition? If yes, go to step 28 . If no, go to step 27 .
22. Check for a leak source in EVAP solenoid vent hose. Repair as necessary Did you find and correct the condition? If yes, go to step 28 . If no, go to step 24 .
23. Check EVAP solenoid vent hose for a blockage or restriction. Repair as necessary. Did you find and correct the condition? If yes, go to step 28 . If no, go to step 24 .
24. Replace EVAP vent solenoid. After repair, go to step 28 .
25. Replace EVAP pressure switching solenoid. After repair, go to step 28 .
26. Replace FTP sensor. After repair, go to step 28 .
27. Replace PCM. After repair, go to next step.
28. Start engine. Select EVAP PURGE SEAL function on scan tool. Command EVAP PURGE SEAL function ON. Does FTP sensor indicate a reading of -12.50 in. H2O for as long as 2 minutes? If yes, go to next step. If no, go to step 4 .
29. With a scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

1. If DTC P0446 is the only EVAP DTC set, the most likely cause is an inoperable EVAP canister vent solenoid, or pressure switching solenoid. Check EVAP solenoids carefully for faulty connections and erratic operation.
2. An intermittent malfunction may be caused by a fault in any of EVAP solenoid electrical circuits. Check wiring harness and components for an intermittent condition.
3. If DTC cannot be duplicated, information included in freeze frame data can be useful in determining vehicle operating conditions when DTC was first set.
4. Operating vehicle in CHECK MODE will increase ability of PCM module to detect engine control system malfunctions. See «SERVICE BAY TESTS»(ref-152429-S19809249722003021000000) under SELF-DIAGNOSTIC SYSTEM.

Engine has been running less than 10 seconds.

1. FTP sensor signal indicates less than 16.3 in. H2O for 7 seconds.
2. FTP sensor signal indicates more than 8.16 in. H2O for 7 seconds.

1. PCM illuminates Malfunction Indicator Light (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with fault active.
2. PCM records operating conditions at the time the diagnostic fails. This information is stored in freeze frame buffer.

1. MIL turns OFF after 3 consecutively passing trips without a fault present.
2. A History DTC clears after 40 consecutive warm-up cycles without a fault.
3. Use scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Loosen fuel tank filler cap to release any pressure inside fuel tank. Turn ignition switch to RUN position, engine OFF. Observe Fuel Tank Pressure (FTP) sensor parameter on scan tool. Is FTP sensor 0.0-0.5 in. H2O? If yes, go to next step. If no, go to step 4 .
3. Use scan tool to clear DTCs. Place vehicle into CHECK MODE using scan tool. See «SERVICE BAY TESTS»(ref-152429-S19809249722003021000000) under SELF-DIAGNOSTIC SYSTEM. Operate vehicle within freeze frame conditions as noted. Does DTC P0450 set? If yes, go to step 6 . If no, go to «DIAGNOSTIC AIDS»(ref-152429-S25454016632003021800000) .
4. Remove FTP sensor. Connect FTP sensor harness connector. Turn ignition switch to RUN position, engine OFF. Observe FTP sensor parameter on scan tool. Is FTP sensor 0.0-0.5 in. H2O? If yes, go to next step. If no, go to step 6 .
5. Repair cause of trapped vapor pressure in fuel tank. After repair, go to step 14 .
6. Turn ignition OFF. Disconnect FTP sensor 3-pin harness connector. Turn ignition switch to RUN position, engine OFF. Use DMM to measure reference circuit voltage on harness side of FTP sensor connector. Does voltage equal 5.0 volts? If yes, go to next step. If no, go to step 8 .
7. Measure voltage from FTP sensor input circuit on harness side using a DMM. Is voltage near 4.9 volts? If yes, go to step 10 . If no, go to step 9 .
8. Repair open in FTP sensor reference voltage circuit between sensor and splice SP108. After repair, go to step 14 .
9. Check FTP sensor input circuit for an open or a short. Verify input circuit is not shorted to sensor ground circuit. Repair as necessary. Was a repair necessary? If yes, go to step 14 . If no, go to step 13 .
10. Probe FTP sensor ground circuit on harness side with a test light connected to battery voltage. Does test light illuminate? If yes, go to step 12 . If no, go to next step.
11. Repair open in FTP sensor ground circuit between sensor and splice in sensor ground circuit. After repair, go to step 14 .
12. Replace FTP sensor. After repair, go to step 14 .
13. Replace PCM. After replacing PCM, go to next step.
14. Use scan tool to clear DTCs. Turn ignition OFF for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S34283794322003020400000) or until EVAP test is complete. Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
15. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

1. If DTCs P0110, P0115, and P0120 are also set, malfunction may be in sensor ground circuit.
2. If a DTC P0120 is also set, malfunction may be in reference voltage circuit.
3. If a DTC P0450 is intermittent, road test vehicle while observing FTP sensor with a scan tool. A momentary reading of -16 in. H2O or less may indicate an intermittent short to ground in sensor input circuit. A momentary reading of 8 in. H2O or more may indicate an open in sensor input or ground circuit.
4. If a DTC P0450 is intermittent, driving vehicle under conditions outlined in Inspection/Maintenance section can verify whether the fault is present. See «INSPECTION/MAINTENANCE EVAP SYSTEM SET PROCEDURE»(ref-152429-S03890597442003020400000) under INSPECTION/MAINTENANCE PROCEDURES (DRIVE CYCLES).
5. EVAP system diagnostic can be monitored on scan tool under I/M SYSTEM INFORMATION selection. When EVAP test displays a YES status, indicating system diagnostic is completed, check for DTC P0450 in LAST TEST FAILED screen of scan tool. If there is no DTC P0450 displayed EVAP system diagnostic has run and passed, indicating no malfunction was present this time. DTCs MUST be cleared to view CURRENT STATUS of the system diagnostics being performed. I/M System Information tests only indicate the test has run, not if the test passed or failed. The LAST TEST FAILED screen must be checked for related DTCs to determine the outcome of the diagnostic test involved.

An intermittent malfunction may be caused by a fault in the sensor electrical circuit. Check wiring harness and components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Repair any electrical circuit faults found. Information included in freeze frame data can be useful in determining vehicle operating conditions when DTC first set.

1. Engine is idling.
2. No vehicle speed is detected.
3. EVAP pressure switching solenoid is OFF.

FTP sensor output voltage rapidly shifts from inside to outside a specified range.

1. PCM illuminates Malfunction Indicator Light (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with fault active.
2. PCM records operating conditions at the time the diagnostic fails. This information is stored in freeze frame buffer.

1. MIL turns OFF after three consecutively passing trips without a fault present.
2. A History DTC clears after 40 consecutive warm-up cycles without a fault.
3. Use scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Loosen fuel tank filler cap to release any pressure inside fuel tank. Turn ignition switch to RUN position, engine OFF. Observe fuel Tank Pressure Sensor (FTP) parameter on scan tool. Is FTP sensor parameter 0.0-0.5 in H2O? If yes, go to next step. If no, go to step 4 .
3. Use scan tool to clear DTCs. Place vehicle into CHECK MODE using scan tool. Refer to «SERVICE BAY TESTS»(ref-152429-S19809249722003021000000) under SELF-DIAGNOSTIC SYSTEM. Operate vehicle within freeze frame conditions as noted. Does the DTC P0451 set? If yes, go to step 6 . If no, go to «DIAGNOSTIC AIDS»(ref-152429-S12520823422003021800000) .
4. Remove FTP sensor. Connect FTP sensor harness connector. Turn ignition switch to RUN position, engine OFF. Observe FTP sensor parameter on scan tool. Is FTP sensor parameter 0.0-0.5 in. H2O? If yes, go next to step. If no, go to 6 .
5. Repair the cause of trapped vapor pressure in fuel tank. After repair, go to step 16 .
6. Turn ignition OFF. Disconnect FTP sensor 3-pin harness connector. Turn ignition switch to RUN position, engine OFF. Use a DMM to measure FTP sensor connector reference circuit voltage (harness side). Does the voltage equal 5 volts? If yes, go to next step. If no, go to step 8 .
7. Connect test light to reference voltage circuit and ground. Turn ignition switch to RUN position, engine OFF. Does the test light illuminate at least dimly? If yes, go to step 9 . If no, go to step 14 .
8. Repair open in FTP sensor reference voltage circuit between sensor and splice SP108. After repair, go to step 16 .
9. Measure FTP sensor input circuit voltage (harness side). Is the voltage near 4.9 volts? If yes, go to step 11 . If no, go to next step.
10. Check FTP sensor input circuit for high resistance. Repair as necessary. Was a repair necessary? If yes, go to step 16 . If no, go to step 15 .
11. Using a test light connected to battery voltage, probe FTP sensor ground circuit (harness side). Does the test light illuminate? If yes, go to step 13 . If no, go to next step.
12. Repair open in FTP sensor ground circuit between sensor and splice in the sensor ground circuit. After repair, go to step 16 .
13. Replace FTP sensor. After repair, go to step 16 .
14. Repair high resistance in reference voltage circuit of FTP sensor. After repair, go to step 16 .
15. Replace PCM. After repair, go to next step.
16. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S18794677192003020400000) or until EVAP test is complete. Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
17. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Check for any of the following conditions

1. Check for a skewed or shifted FTP sensor.
2. If a DTC P0451 is intermittent, driving vehicle under conditions outlined in Inspection/Maintenance System Information section can verify whether the fault is present. See «INSPECTION/MAINTENANCE EVAP SYSTEM SET PROCEDURE»(ref-152429-S03890597442003020400000) under INSPECTION/MAINTENANCE PROCEDURES (DRIVE CYCLES).
3. EVAP system diagnostic can be monitored on scan tool under I/M System Information selection. When EVAP test displays a YES status, indicating the system diagnostic is completed, check for DTC P0451 in LAST TEST FAILED screen of scan tool. If there is no DTC P0451 displayed, EVAP system diagnostic has run and passed, indicating no malfunction was present this time. DTCs MUST be cleared to view CURRENT STATUS of system diagnostics being performed. I/M System Information tests only indicate the test has run, not if test passed or failed. The LAST TEST FAILED screen must be checked for related DTCs to determine the outcome of the diagnostic test involved.

An intermittent malfunction may be caused by a fault in FTP sensor electrical circuit. Check wiring harness and components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Repair any electrical circuit faults found. Information included in freeze frame data can be useful in determining vehicle operating conditions when DTC first set.

Engine is running.

1. No vehicle speed sensor signal is sent to PCM.
2. Park/Neutral position switch is OFF.
3. Engine speed is equal to or more than 2350 RPM.
4. Throttle Position (TP) angle is equal to or more than 13 degrees.
5. Engine parameters indicate vehicle is being driven.

1. PCM illuminates the Malfunction Indicator Light (MIL) the first time the diagnostic runs with the fault active.
2. PCM records operating conditions at the time the diagnostic fails. This information is stored in freeze frame buffer.

1. MIL turns OFF after 3 consecutively passing trips without a fault present.
2. A History DTC clears after 40 consecutive warm-up cycles without a fault.
3. Use the scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Raise and support drive wheels. Support lower control arms so drive axles are in a horizontal position. Start and idle engine. Observe VEHICLE SPEED parameter on scan tool. Allow engine to idle in gear with drive wheels rotating. Does scan tool parameter indicate a vehicle speed? If yes, go to next step. If no, go to step 4 .
3. Using scan tool, store DTC freeze frame information. Use scan tool to clear DTCs. Place vehicle into CHECK MODE using scan tool. Operate vehicle within freeze frame conditions. Does DTC P0500 set? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(ref-152429-S24266836332003021800000) .
4. Observe speedometer with engine at idle in gear with drive wheels rotating. Does speedometer indicate a vehicle speed? If yes, go to step 10 . If no, go to next step.
5. Do all other instrument cluster assembly functions operate normally? If yes, go to next step. If no, go to INSTRUMENT PANEL - VIBE article in ACCESSORIES & EQUIPMENT.
6. Turn ignition OFF. Disconnect VSS harness connector. Turn ignition switch to RUN position, engine OFF. Probe VSS connector terminal No. 1 on harness side using a test light connected to ground. Does test light illuminate? If yes, go to next step. If no, go to step 12 .
7. Using a test light connected to battery voltage, probe VSS harness connector terminal No. 2. Does test light illuminate? If yes, go to next step. If no, go to step 13 .
8. With a test light connected to battery voltage, probe VSS harness connector terminal No. 3 (harness side). Does test light illuminate? If yes, go to step 14 . If no, go to next step.
9. Reconnect VSS connector. Disconnect Instrument Panel Cluster (IPC) harness connector. Set-up Digital Multimeter (DMM) to measure the DC frequency on speedometer vehicle speed input circuit terminal No. 18. Start and idle engine. Allow engine to idle in gear with drive wheels rotating. Does DMM indicate a frequency? If yes, go to step 18 . If no, go to step 15 .
10. Turn ignition switch to OFF position. Disconnect PCM harness White 35-pin connector C3, containing the vehicle speed input terminal. Turn ignition switch to RUN position, engine OFF. Probe vehicle speed input circuit terminal on harness side with DMM connected to ground. Measure DC voltage on the vehicle speed input circuit. Is the voltage 9-12 volts? If yes, go to next step. If no, go to step 16 .
11. Set-up the DMM to measure DC frequency on PCM vehicle speed input circuit. Start and idle engine. Allow engine to idle in gear with drive wheels rotating. Does DMM indicate a frequency? If yes, go to step 20 . If no, go to step 17 .
12. Repair cause of no power to VSS connector. After repair, go to step 21 .
13. Repair cause of no ground to VSS connector. After repair, go to step 21 .
14. Check speedometer vehicle speed input circuit for a short to ground. Repair as necessary. Was a repair necessary? If yes, go to step 21 . If no, go to step 18 .
15. Check speedometer vehicle speed input circuit for an open. Repair as necessary. Was a repair necessary? If yes, go to step 21 . If no, go to step 19 .
16. Check PCM vehicle speed input circuit for a short to ground or open. If equipped, ensure cruise control module is not shorted internally. See CRUISE CONTROL SYSTEMS - VIBE article in ACCESSORIES & EQUIPMENT. Repair as necessary. Was a repair necessary? If yes, go to step 21 . If no, go to step 18 .
17. Check PCM vehicle speed input circuit for a short to battery voltage. Repair as necessary. Was a repair necessary? If yes, go to step 21 . If no, go to step 18 .
18. Replace speedometer. After repair, go to step 21 .
19. Replace VSS. After repair, go to step 21 .
20. Replace PCM. After repair, go to next step.
21. Use scan tool to clear DTCs and road test vehicle within freeze frame conditions that set the DTC. Review scan tool data and check for DTCs. Repair is complete if no DTCs are stored. Are any DTCs displayed on scan tool? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

A scan tool should indicate a vehicle speed whenever drive wheels are turning at a speed of more than 3 MPH (5 km/h). DTC P0500 can be falsely set if engine is brake-torqued in gear. Disregard DTC P0500 if the DTC sets when drive wheels are not turning.

An intermittent malfunction may be caused by a fault in VSS sensor electrical circuit. Check wiring harness and related components for any of the following conditions

1. Any backed-out terminals.
2. Any improper mating of terminals.
3. Any broken electrical connector locks.
4. Any improperly formed or damaged terminals.
5. Any faulty terminal-to-wire connections.
6. Any physical damage to the wiring harness.
7. A broken wire inside the insulation.
8. Any corrosion of electrical connections, splices, or terminals.

Repair any electrical circuit faults found. Information included in freeze frame data can be useful in determining vehicle operating conditions when DTC first set.

Engine is running.

PCM determines that actual idle speed varies greatly from desired idle speed.

1. PCM illuminates Malfunction Indicator Light (MIL) the first time the diagnostic runs with fault active.
2. PCM stores conditions which were present when DTC set as freeze frame data.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Start and idle engine until engine reaches normal operating temperature. Using scan tool, store freeze frame and DTC information. Turn ignition OFF and wait 30 seconds. Turn ignition switch to RUN position, engine OFF. Use scan tool to clear DTCs. Start and idle engine. Wait 60 seconds, then check for stored DTCs. Does this DTC reset? If yes, go to step 4 . If no, go to next step.
3. Is there an idle quality concern? If yes, go to «ROUGH, UNSTABLE, OR INCORRECT IDLE AND STALLING»(ref-153013-S30729456532003031100000) under SYMPTOM DIAGNOSIS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. If no, go to «DIAGNOSTIC AIDS»(ref-152429-S01577678862003020400000) .
4. Turn ignition OFF. Disconnect IAC valve 3-pin harness connector. Turn ignition switch to RUN position, engine OFF. Using test light connected to ground, probe terminal No. 2 of the IAC valve harness connector. Does test light illuminate? If yes, go to next step. If no, go to step 8 .
5. Using test light connected to battery voltage, probe IAC valve harness connector terminal No. 3. Does test light illuminate? If yes, go to next step. If no, go to step 8 .
6. Turn ignition OFF. Jump terminal No. 2 of IAC valve connector on the harness side to terminal No. 2 of the IAC valve with a fused jumper wire. Jump terminal No. 3 of IAC valve connector on harness side to terminal No. 3 of the IAC valve with a fused jumper wire. Connect a fused jumper wire to terminal No. 1 of IAC valve (component side). Insulate terminal No. 1 jumper from contact to ground. Start and idle the engine. With engine idling, repeatedly touch the terminal No. 1 jumper to battery ground with a rapid ON-OFF motion. Does engine speed increase as terminal No. 1 jumper is rapidly grounded ON and OFF? If yes, go to next step. If no, go to step 10 .
7. Turn ignition OFF. Remove all jumpers. Disconnect PCM White 34-pin harness connector (containing IAC valve open control circuit). Check IAC valve open control circuit, terminal No. 1, for a grounded, open, or short to voltage circuit. Repair circuit as necessary. Was a circuit repair made? If yes, go to step 12 . If no, go to step 11 .
8. Locate cause of no power to IAC valve connector. Refer to «TEST DESCRIPTION»(ref-152429-S06058991492003020400000) . Repair as necessary. After repair, go to step 12 .
9. Repair open IAC valve ground circuit. After repair, go to step 12 .
10. Replace IAC valve. After repair, go to step 12 .
11. Replace PCM. After repair, go to next step.
12. Use scan tool to clear DTCs. Turn ignition OFF for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S09913468702003020400000) as specified. Are any DTCs displayed on scan tool? If yes, go to next step. If no, go to step 2 .
13. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no other DTCs are displayed, system is okay at this time.

With engine idling at normal operating temperature and all accessories OFF, monitor the following parameters on scan tool for correct operation

1. IAC Motor Command - 25-45 percent.
2. Electrical load - No.
3. Commanded A/C - OFF.

Scan tool can be used to isolate the cause of an intermittent DTC P0505. Engine idle speed can be controlled sing the scan tool. Operate IAC valve using scan tool while checking for a smooth increase and decrease in engine speed. If engine speed can be controlled, IAC system is functioning normally. Check for the following conditions

1. Any blockage of air intake system.
2. Any blockage of IAC passage.
3. Excessive deposits on throttle plate or throttle bore.
4. Any large vacuum leaks.

An intermittent malfunction may be caused by a fault in IAC sensor electrical circuit. Check wiring harness and related components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Repair any electrical circuit faults found. Information included in freeze frame data can be useful in determining vehicle operating conditions when DTC first set. If DTC P0505 does not reset, but a driveability symptom still exists, diagnose by symptom. See TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.

1. PCM turns MIL OFF on the third consecutive trip cycle during which the diagnostic has run and fault condition is no longer present.
2. A DTC will clear after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Use scan tool to clear DTCs. Start engine. Run engine to obtain normal operating temperature. Does DTC P1600 set? If yes, go to next step. If no, see «INTERMITTENTS»(ref-153013-S39990244982003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.
3. Turn ignition OFF. Disconnect PCM harness White 34-pin connector C4. Measure voltage of battery voltage circuit using a DMM. Does DMM indicate battery voltage? If yes, go to step 5 . If no, go to next step.
4. Repair open in battery positive voltage circuit between PCM and underhood fuse block. After repair, go to step 6 .
5. Replace PCM. After replacing PCM, go to next step.
6. Use scan tool to clear DTCs. Start engine. Run engine to obtain normal operating temperature. Check for DTC P1600. Is DTC P1600 present? If yes, go to step 2 . If no, go to next step.
7. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

DTC P0710 sets when one of the following conditions occurs

1. Condition 1 - Transmission Fluid Temperature sensor resistance is less than 79 ohms.
2. Condition 2 - After engine has been operating for 15 minutes or more, and resistance at temperature sensor is more than 156 k/ohms.

1. A scan tool can clear DTC.
2. PCM clears DTC from PCM history if vehicle completes 40 warm-up cycles without a non-emission related diagnostic fault occurring.
3. PCM cancels DTC default actions when fault no longer exists and DTC passes.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Did you perform Transmission Fluid Checking Procedure? If yes, go to next step. If no, go to appropriate SERVICING article in AUTOMATIC TRANSMISSIONS.
3. Install scan tool. Turn ignition switch to RUN position, engine OFF. Record FAILURE RECORDS. Use scan tool to clear DTCs. Drive vehicle for at least 7 minutes. Using scan tool, observe TFT for rapid fluctuations in temperature. Record temperature at start and end of the trip. Was transmission fluid temperature 122-176°F (50-80°C)? If yes, go to step 9 . If no, go to next step.
4. Turn ignition switch to LOCK position. Disconnect PCM White 34-pin harness connector C1. Use a Digital Multi Meter (DMM) to measure resistance between PCM harness connector C1 terminals No. 28 and 30. Is resistance equal to 6.4 k/ohms at 50°F (10°C) and 0.2 k/ohms at 230°F (110°C)? If yes, go to step 9 . If no, go to next step.
5. Disconnect transmission Gray, 6-pin connector at the transmission. Use DMM to measure resistance between terminals No. 1 and 6 on transmission component connector. Is resistance equal to 6.4 k/ohms at 50°F (10°C) and 0.2 k/ohms at 230°F (110°C)? If yes, go to next step. If no, go to step 8 .
6. Disconnect PCM White 34-pin harness connector C1. Check transmission temperature sensor circuit between PCM and transmission connector for an open or high resistance. Did you find and correct the condition? If yes, go to step 12 . If no, go to next step.
7. Disconnect the PCM harness connector C1. Check the transmission temperature sensor signal circuit between PCM and transmission connector for a short to ground. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 10 .
8. Remove transmission oil pan. Check terminals and internal harness for damage. Replace TFT sensor if no damage exists. After repair, go to step 12 .
9. Install a known-good PCM. Use scan tool to clear DTCs. Check for DTCs. Does DTC P0710 reset? If yes, go to next step. If no, go to step 11 .
10. Check for a possible intermittent condition. See «INTERMITTENTS»(ref-153013-S39990244982003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. After repair, go to step 12 .
11. Replace PCM. After repair, go to step 12 .
12. Turn ignition switch to LOCK position. Reconnect all connectors. Use scan tool to clear DTCs. Recheck for DTCs. Does the scan tool display any DTCs? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Ignition switch is in RUN position.

No ignition coil fail-safe input signal to PCM for 2 consecutive ignition trigger signal cycles, when engine is cranking or running.

1. PCM illuminates Malfunction Indicator Light (MIL).
2. PCM stores conditions that were present when DTC set as freeze frame data.
3. PCM enters fail-safe function and begins FUEL CUT-OFF mode operation during high engine load operation.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Are DTCs P1305, P1310, and P1315 also set? If yes, go to step 11 . If no, go to next step.
3. Start engine. Is an engine misfire present? If yes, go to next step. If no, go to step 9 .
4. Turn ignition switch to OFF position. Disconnect ignition coil harness connector of the coil indicated by the DTC. Turn ignition switch to RUN position, engine OFF. Probe the ignition positive voltage circuit on harness side of ignition coil connector with a test light connected to ground. Does test light illuminate? If yes, go to next step. If no, go to step 7 .
5. Use scan tool to clear DTCs. Probe ignition trigger signal circuit on harness side of ignition coil connector with a DMM connected to ground. Measure circuit voltage while cranking engine. Is voltage 0.2-1.0 volt? If yes, go to next step. If no, go to step 8 .
6. Probe ground circuit on harness side of ignition coil connector with a test light connected to battery voltage. Does test light illuminate? If yes, go to «DIAGNOSTIC AIDS»(ref-152429-S38289316842003020400000) . If no, go to step 10 .
7. Repair open or short in ignition power circuit between the ignition coil and splice SP106. After repair, go to step 18 .
8. Check low reference circuit of the MAP sensor for an open. Did you find and correct the condition? If yes, go to step 18 . If no, go to step 17 .
9. Check for an open in ignition fail-safe input circuit between the ignition coil and splice SP108. Repair as necessary. Did you find and correct a condition? If yes, go to step 18 . If no, go to step 16 .
10. Repair open in ignition ground circuit between ignition coil and splice SP105. After repair, go to step 18 .
11. Use scan tool to clear DTCs. Turn ignition OFF for 10 seconds. Turn ignition switch to RUN position, then attempt to start the engine. Did engine start and run smoothly with no engine misfire? If yes, go to step 14 . If no, go to next step.
12. Turn ignition switch to OFF position. Disconnect harness connector from cylinder 1 ignition coil. Turn ignition switch to RUN position, engine OFF. Probe ignition coil connector ignition positive voltage circuit (harness side) using a test light connected to ground. Does test light illuminate? If yes, go to step 15 . If no, go to next step.
13. Check for any of the following faults in the ignition positive voltage circuits of ignition coils: An open in the circuit between splice SP106 and instrument panel fuse block. A short in the circuit between splice SP106, the instrument panel fuse block, or the noise filter. A shorted noise filter. Repair or replace as necessary. After repair, go to step 18 .
14. Check for any of the following faults in ignition fail-safe input circuit: An open circuit between PCM and splice SP108. A short to ground between PCM and ignition coils. A short to voltage between PCM and ignition coils. Repair as necessary. Did you find and correct a condition? If yes, go to step 18 . If no, go to step 17 .
15. Repair faulty ignition coil ground circuit between splice SP105 and ground point G105. After repair, go to step 18 .
16. Replace faulty ignition coil. After repair, go to step 18 .
17. Replace PCM. After repair, go to next step.
18. Use scan tool to clear DTCs. Turn ignition OFF for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S38386030542003020400000) as specified. Does DTC run and pass? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Check for the following conditions

1. An interruption of ground circuit or voltage supply to ignition coils will prevent a proper ignition event from taking place. DTC P1300 through P1315 will set if there is a fault in any ignition coil circuits.
2. If DTCs P1305, P1310, and P1315 are present, fault is located in shared electrical circuits or shared components of ignition coils.
3. Check ignition coil grounds at ground point G105 for a clean and tight connection.
4. If no engine misfire is felt when DTC sets, check for a fault in Ignition Fail-Safe Input circuit. Check the noise filter for an internal short or low resistance. The ignition coil may not receive adequate voltage during high load conditions if noise filter is faulty. A good noise filter will indicate infinite resistance with a DMM after the capacitor inside the filter is charged up.
5. Unless ignition key is cycled or DTCs are cleared, PCM waits to receive ignition fail-safe signals before providing fuel injector operation.

An intermittent malfunction may be caused by a fault in the ignition coil electrical circuit. Check wiring harness and related components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Repair any electrical circuit faults found. Information included in freeze frame data can be useful in determining vehicle operating conditions when DTC first set.

Engine speed is more than 1000 RPM.

Crankshaft Position (CKP) sensor input is not detected for over 50 ms while engine is running.

1. PCM illuminates Malfunction Indicator Light (MIL) during the second key cycle in which DTC sets.
2. PCM stores conditions which were present when DTC set as freeze frame data.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Use scan tool to clear DTCs. Using scan tool, place vehicle into CHECK MODE. See «SERVICE BAY TESTS»(ref-152429-S19809249722003021000000) under SELF-DIAGNOSTIC SYSTEM. Operate vehicle within freeze frame conditions as noted. Does DTC P1335 set? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(ref-152429-S07268695902003021900000) .
3. Turn ignition switch to OFF position. Measure resistance of CKP sensor, using a DMM. Is resistance 985-1670 ohms at 122°F (50°C) or 1265-1890 ohms at 212°F (100°C)? If yes, go to next step. If no, go to step 6 .
4. Disconnect PCM White 34-pin harness connector. Check for a open or short in CKP circuits. Repair as necessary. Was a repair necessary? If yes, go to step 8 . If no, go to next step.
5. Check for a faulty electrical connection at PCM and CKP sensor. Repair as necessary. Was a repair necessary? If yes, go to step 8 . If no, go to next step.
6. Replace CKP sensor. After repair, go to step 8 .
7. Replace PCM. After repair, go to step 8 .
8. Use scan tool to clear DTCs. Turn ignition OFF for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S23388655952003020400000) as specified. Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
9. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

A DTC P1335 can be the result of a defective reluctor wheel. Remove CKP sensor and check the reluctor wheel through sensor hole. Check reluctor wheel for porosity, nicks, dents, etc. and repair as necessary. An intermittent malfunction may be caused by a fault in CKP sensor electrical circuit. Check wiring harness and related components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Repair any electrical circuit faults found. Information included in freeze frame data can be useful in determining vehicle operating conditions when DTC first set.

1. Engine is running.
2. Engine coolant temperature is more than 158°F (70°C).
3. Vehicle is operating at more than 5 MPH (8 km/h).

1. PCM detects an unexpected deviation in the relationship of input signals of CMP and CKP sensors.
2. Fault is present several times during a driving event.

1. PCM illuminates Malfunction Indicator Light (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with fault active.
2. PCM stores conditions that were present when DTC set as freeze frame data.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. A DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Is DTC P1656 or P1349 present? If yes, go to «DTC P1656: INTAKE CAMSHAFT POSITION ACTUATOR SOLENOID CONTROL CIRCUIT»(ref-152429-S13656126492003020400000) or «DTC P1349: INTAKE CMP SYSTEM PERFORMANCE»(ref-152429-S18074355752003020400000) . If no, go to next step.
3. Start engine. Allow engine to reach normal operating temperature. Command CMP actuator solenoid ON using scan tool. Does engine idle very rough or stall when CMP actuator solenoid is commanded ON? If yes, go to «DIAGNOSTIC AIDS»(ref-152429-S15850711222003021900000) . If no, go to next step.
4. Turn ignition switch to OFF position. Remove CMP actuator solenoid. Connect CMP actuator solenoid to battery voltage and to ground with a pair of fused jumper wires. Observe movement of solenoid plunger when voltage is applied and released. Does solenoid plunger extend to at least 0.125" (3 mm) when voltage is applied and then retract when voltage is removed? If yes, go to next step. If no, go to step 6 .
5. Check the engine for the following engine mechanical concerns: A damaged or misaligned CMP sensor reluctor. A worn timing chain and jumped timing. A damaged CMP sensor reluctor wheel. An incorrectly installed or incorrectly timed camshaft. Low oil pressure or oil supply to CMP actuator assembly or actuator solenoid. Repair as necessary. See appropriate article in ENGINES. Was a repair necessary? If yes, go to step 8 . If no, go to step 7 .
6. Replace CMP actuator solenoid valve. After repair, go to step 8 .
7. Replace PCM. After repair, go to step 8 .
8. Use scan tool clear DTCs. Turn ignition OFF for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S32545732032003020400000) as specified in supporting text. Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
9. With a scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Check for any recent engine mechanical repairs. An incorrectly timed or incorrectly installed camshaft can cause a DTC P1346 to set. If a DTC P1349 and P1346 are both present, Check for a malfunctioning CMP solenoid valve. Observe Cam Phase Angle and Cam Phase Angle Desired parameters on scan tool are approximately equal. A difference in the two parameters indicates CMP solenoid may be sticking. An intermittent malfunction may be caused by a fault in the electrical circuit of the CMP actuator valve. Check wiring harness and related components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Information included in freeze frame data can be useful in determining vehicle operating conditions when DTC first set.

1. Engine is running.
2. Engine coolant temperature is more than 158°F (70°C).
3. Engine speed is 400-4000 RPM.
4. Vehicle speed is more than 5 MPH (8 km/h).

1. PCM does not detect a change in camshaft timing when CMP actuator solenoid is activated.
2. PCM detects camshaft timing is fixed.
3. Either condition is present more than once during a driving event.

1. PCM illuminates Malfunction Indicator Light (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with fault active.
2. PCM stores conditions present when DTC set as freeze frame data.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. A DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Disconnect CMP actuator solenoid valve. Measure resistance of solenoid using a DMM. Is resistance 6.9-7.9 ohms at 68°F (20°C)? If yes, go to next step. If no, go to step 10 .
3. Connect CMP solenoid valve. Start engine. Allow engine to reach normal operating temperature. Command CMP actuator solenoid ON using scan tool. Does engine idle very rough or stall when CMP actuator solenoid is commanded ON? If yes, go to «DIAGNOSTIC AIDS»(ref-152429-S00026968762003021900000) . If no, go to next step.
4. Remove CMP actuator solenoid valve. Connect CMP actuator solenoid to battery voltage and ground with fused jumper wires. Observe movement of solenoid plunger when power is applied and released. Does solenoid plunger extend to at least 0.125" (3 mm) when voltage is applied and then retract when voltage is removed? If yes, go to next step. If no, go to step 10 .
5. Remove CMP actuator solenoid oil filter. Check oil filter for restrictions or blockage. Is CMP actuator solenoid oil filter restricted or blocked? If yes, go to step 9 . If no, go to step 10 .
6. Check engine for correct engine valve timing. Check CMP actuator oil passages for blockage or restrictions. Repair as necessary. See appropriate article in ENGINES. Was a repair necessary? If yes, go to step 13 . If no, go to next step.
7. Install CMP actuator solenoid valve. Connect CMP actuator solenoid. Use scan tool to clear DTCs. Backprobe between CMP actuator solenoid circuits with a DMM. Start engine. Observe DC voltage on DMM while operating CMP solenoid with scan tool. Was voltage 0.7-1.0 volt with solenoid OFF, and 8.0-10.0 volts with solenoid ON? If yes, go to step 11 . If no, go to next step.
8. Check CMP actuator solenoid valve electrical circuit for high resistance in circuit wiring or connections. Repair as necessary. Was a repair necessary? If yes, go to step 13 . If no, go to step 12 .
9. Clean or replace CMP actuator solenoid filter. Install CMP actuator solenoid valve. After repair, go to step 13 .
10. Replace CMP actuator solenoid valve. After repair, go to step 13 .
11. Replace CMP actuator assembly. After repair, go to step 13 .
12. Replace PCM. After repair, go to next step.
13. Use scan tool to clear DTCs. Turn ignition OFF for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S33782525952003020400000) as specified. Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
14. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Check for any of the following conditions

1. Check for any recent engine mechanical repairs. An incorrectly timed or incorrectly installed camshaft can cause a DTC P1349 to set.
2. Check CMP sensor reluctor for a damaged tooth. A damaged reluctor can cause an incorrect CMP sensor reading that may set a false DTC P1349.
3. If a DTC P1349 and P1346 are both present, Check for a malfunctioning CMP solenoid valve. Observe Cam Phase Angle and Cam Phase Angle Desired parameters on scan tool are approximately equal. A difference in the two parameters indicates CMP solenoid may be sticking.
4. An intermittent DTC P1349 can be caused by a loss in the oil supply to CMP solenoid valve or CMP actuator assembly. Check oil passages for foreign material and blockage. Check oil filter of CMP actuator solenoid valve for dirt or restrictions.

An intermittent malfunction may be caused by a fault in the electrical circuit of CMP actuator valve. Check wiring harness and components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Information included in freeze frame data can be useful in determining vehicle operating conditions when DTC first set.

Ignition switch is in RUN position.

PCM detects an open or a short in CMP actuator solenoid control circuit.

1. PCM illuminates Malfunction Indicator Light (MIL).
2. PCM stores conditions present when DTC set as freeze frame data.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. A DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Use scan tool to clear DTCs. Start engine. Operate engine for one minute. Review scan tool data and check for DTC P1656. Is DTC P1656 set? If yes, go to step 4 . If no, go to next step.
3. Start engine. Allow engine to reach normal operating temperature. Using scan tool, command CMP actuator solenoid ON. Does engine idle very rough or stall when CMP actuator solenoid is commanded ON? If yes, see «INTERMITTENTS»(ref-153013-S39990244982003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. If no, go to next step.
4. Start engine. Allow engine to reach normal operating temperature. Turn engine OFF. Disconnect harness connector to CMP actuator solenoid valve. Start and idle engine. Using a pair of fused jumper wires, connect CMP actuator solenoid to battery voltage and ground. Does engine idle very rough or stall when CMP actuator solenoid is connected to battery voltage? If yes, go to next step. If no, go to step 7 .
5. Check CMP Actuator High Control circuit for an open or a short. Repair as necessary. Was a repair necessary? If yes, go to step 10 . If no, go to next step.
6. Check CMP Actuator Low Control circuit for an open or a short. Repair as necessary. Was a repair necessary? If yes, go to step 10 . If no, go to step 8 .
7. Replace CMP actuator solenoid valve. After repair, go to step 10 .
8. Check electrical circuits and connections of CMP actuator solenoid for high electrical resistance. Check PCM and CMP actuator solenoid for poor connections at the harness connectors. Repair as necessary. Was a repair necessary? If yes, go to step 10 . If no, go to next step.
9. Replace PCM. After repair, go to next step.
10. Use scan tool to clear DTCs. Turn ignition OFF for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S13971489272003020400000) . Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
11. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

Ignition switch is in RUN position.

PCM detects an open or a short in control circuit of rocker arm oil control solenoid.

1. PCM illuminates Malfunction Indicator Light (MIL).
2. PCM stores conditions present when DTC set as freeze frame data.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. A DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Use scan tool to clear DTCs. Start engine. Operate engine for one minute. Review scan tool data and check for DTC P1690. Is DTC P1690 set? If yes, go to step 4 . If no, go to next step.
3. Start engine. Allow engine to reach normal operating temperature. With transmission in Neutral, increase engine speed to 1500-2500 RPM. Using scan tool, command rocker arm oil control solenoid ON. Does engine idle very rough or stall when the rocker arm oil control solenoid is commanded ON? If yes, see «INTERMITTENTS»(ref-153013-S39990244982003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. If no, go to next step.
4. Start engine. Ensure engine has reached operating temperature. Turn engine OFF. Disconnect harness connector to rocker arm oil control solenoid valve. Start engine. With transmission in Neutral, increase engine speed to 1500-2500 RPM. Connect rocker arm oil control solenoid to battery voltage and ground with a pair of fused jumper wires. Does engine idle very rough or stall when rocker arm oil control solenoid is connected to battery voltage? If yes, go to next step. If no, go to step 7 .
5. Check control high circuit of rocker arm oil control solenoid for an open or a short. Repair as necessary. Was a repair necessary? If yes, go to step 10 . If no, go to next step.
6. Check control low circuit of rocker arm oil control solenoid for an open or a short. Repair as necessary. Was a repair necessary? If yes, go to step 10 . If no, go to step 8 .
7. Replace rocker arm oil control solenoid. After repair, go to step 10 .
8. Check electrical circuits and connections of rocker arm oil control solenoid for high electrical resistance. Check for poor connections at harness connectors of PCM and rocker arm oil control solenoid. Repair as necessary. Was a repair necessary? If yes, go to step 10 . If no, go to next step.
9. Replace PCM. After repair, go to next step.
10. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S37084614902003020400000) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
11. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

1. Engine is running.
2. Engine speed is less than 6000 RPM.

1. Signal circuit of the rocker arm oil pressure switch stays high.
2. Condition is present for at least 5 seconds.

Action Taken When the DTC Sets

1. PCM illuminates Malfunction Indicator Light (MIL).
2. PCM stores conditions present when DTC set as freeze frame data.

1. PCM turns OFF MIL on the third consecutive trip cycle during which the diagnostic has been run and fault condition is no longer present.
2. A DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Is engine running rough or stalling? If yes, go to step 5 . If no, go to next step.
3. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Run engine at idle for one minute. Did a DTC P1692 set? If yes, go to step 7 . If no, go to next step.
4. Operate vehicle within freeze frame conditions as specified. Did a DTC P1692 set? If yes, go to step 9 . If no, see «INTERMITTENTS»(ref-153013-S39990244982003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.
5. Disconnect harness connector of rocker arm oil control solenoid. Start engine. Is engine still running rough or stalling? If yes, go to step 11 . If no, go to next step.
6. Check for a short to voltage or a short to ground in electrical circuits of rocker arm oil control solenoid. Repair as necessary. Did you find and correct a condition? If yes, go to step 15 . If no, go to step 16 .
7. Disconnect harness connector of rocker arm oil pressure switch. Measure resistance of rocker arm oil pressure switch. Is resistance less than 3 ohms? If yes, go to next step. If no, go to step 13 .
8. Check for an open in input circuit of rocker arm oil pressure switch. Check for poor electrical connections at rocker arm oil pressure switch or PCM. Repair as necessary. Did you find and correct a condition? If yes, go to step 15 . If no, go to next step.
9. Remove rocker arm oil control solenoid. Turn ignition switch to RUN position, engine OFF. Connect rocker arm oil control solenoid to battery voltage and ground with a pair of fused jumper wires. Observe movement of solenoid plunger when voltage is applied and removed. Does solenoid plunger extend to 0.125" (3 mm) when voltage is applied and then retract smoothly when voltage is removed? If yes, go to next step. If no, go to step 12 .
10. Check for an intermittent short to voltage or short to ground in electrical circuits of rocker arm oil control solenoid. Repair as necessary. Did you find and correct a condition? If yes, go to step 15 . If no, go to step 14 .
11. Check for a restriction or blockage in the oil return passage of rocker arm oil control system. Repair as necessary. Did you find and correct a condition? If yes, go to step 15 . If no, go to next step.
12. Replace rocker arm oil control solenoid valve. After repair, go to step 15 .
13. Replace rocker arm oil pressure switch. After repair, go to step 15 .
14. Replace PCM. After repair, go to next step.
15. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within «CONDITIONS FOR RUNNING DTC»(ref-152429-S08880609962003020400000) . Does DTC run and pass? If yes, go to next step. If no, go to step 2 .
16. Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.

1. The engine is running.
2. The Engine Coolant Temperature (ECT) is at least 140°F (60°C).
3. Engine speed is more than 6000 RPM.

1. The signal circuit of the rocker arm oil pressure switch stays low.
2. The condition is present for at least one second.

1. The PCM illuminates the malfunction indicator Light (MIL).
2. The PCM stores the conditions that were present when the DTC set as FREEZE FRAME data.

1. The PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
2. A DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
3. A DTC can be cleared by using the scan tool CLEAR DTC INFORMATION function.

1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-152429-S10298708072003020400000) under SELF-DIAGNOSTIC SYSTEM.
2. Disconnect the rocker arm oil control solenoid. Measure the resistance of the solenoid with a DMM. Is the resistance within the specified range? If yes, go to next step. If no, go to step 12 .
3. Start the engine. Allow the engine to reach normal operating temperature. With the transmission in Neutral, increase the engine speed to 1500-2500 RPM. Command the rocker arm oil control solenoid ON with a scan tool. Does the engine idle very rough or stall when the rocker arm oil control solenoid is commanded ON? If yes, go to step 7 . If no, go to next step.
4. Turn ignition switch to OFF position. Remove rocker arm oil control solenoid. Using a pair of fused jumper wires, connect rocker arm oil control solenoid to battery voltage and ground. Observe the movement of the solenoid plunger when electrical voltage is applied and removed. Does the solenoid plunger extend to 0.125" (3 mm) when voltage is applied and then retract smoothly when voltage is removed? If yes, go to next step. If no, go to step 11 .
5. Remove the rocker arm oil control solenoid oil filter. Check the oil filter for restrictions or blockage. Is the rocker arm oil control solenoid oil filter restricted or blocked? If yes, go to step 10 . If no, go to next step.
6. Check for the following conditions: Blockage or restrictions in the oil passages of the rocker arm oil control solenoid housing. Blockage or restrictions in the cylinder head oil passages or rocker arm shafts. The correct operation of the rocker arm shafts and rocker arms. Repair as necessary. Go to appropriate article in ENGINES. After repair, go to step 15 .
7. Disconnect rocker arm oil pressure switch harness connector. Connect a DMM to the oil pressure switch harness connector and ground. Turn ignition switch to RUN position, engine OFF. Measure DC voltage. Is the voltage more than 11.0 volts? If yes, go to next step. If no, go to step 9 .
8. Connect a test light to battery voltage and oil pressure switch terminal. Start engine. Test light should be illuminated. With transmission in Neutral and the engine at normal operating temperature, increase engine speed to 1500-2500 RPM. Observe test light while commanding the rocker arm oil control solenoid ON using the scan tool. Did test light turn OFF when the rocker arm oil control solenoid was commanded ON? If yes, see «INTERMITTENTS»(ref-153013-S39990244982003031100000) in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. If no, go to step 13 .
9. Check for a short to ground in rocker arm oil pressure switch input circuit. Repair as necessary. Did you find and correct a condition? If yes, go to step 15 . If no, go to step 14 .
10. Clean or replace rocker arm oil control solenoid filter. Install the rocker arm oil control solenoid. After repair, go to step 15 .
11. Check rocker arm oil control solenoid electrical circuit for high resistance in the circuit wiring or connections. Repair as necessary. Did you find and correct a condition? If yes, go to step 15 . If no, go to next step.
12. Replace rocker arm oil control solenoid valve. After repair, go to step 15 .
13. Replace rocker arm oil pressure switch. After repair, go to step 15 .
14. Replace PCM. After repair, go to next step.
15. Using scan tool, observe stored information, CAPTURE INFO. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay.
16. With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-152429-S35671638322003020400000) . If no, system is okay at this time.