Diagnostic Procedures
- Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM.
- Incorrect CKP System Variation data in the PCM may cause DTC P0300 to set with no apparent misfire. Any of the following conditions can cause incorrect CKP System Variation data:
- Replacing the engine.
- Replacing the PCM.
- Reprogramming the PCM.
- Replacing the CKP sensor.
- Performing internal engine repairs that affect the CKP sensor to crankshaft reluctor wheel relationship.
If any of the above conditions apply to this vehicle, the CKP System Variation Learn Procedure must be performed before proceeding with misfire diagnosis. See CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE under PROGRAMMING. Are any other DTCs set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
- Start the engine. Select the Misfire Bar Graph on the scan tool, the Misfire Current counters can also be used. Do any cylinders indicate an excessive amount of misfire? If yes, go to next step. If no, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.
- Does the misfire appear to be affecting specific cylinders? If yes, go to step 9. If no, go to next step.
- Visually and physically inspect the following system grounds:
- PCM grounds.
- Ignition control module grounds.
Ensure that the ground are clean, tight, and in their proper locations. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step 14. If no, go to next step.
- Start and idle the engine. Does the scan tool indicate a varying HO2S sensor 1 voltage? If yes, go to next step. If no, see DTC P0132 & P0152: HO2S BANK 1 & 2 SENSOR 1 CIRCUIT - HIGH VOLTAGE .
- Test the fuel pressure. See appropriate BASIC DIAGNOSTIC PROCEDURES article. If a fuel system pressure condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step 14. If no, go to next step.
- Test for excessive water, alcohol, or other contaminants. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step 14. If no, go to next step.
- Visually and physically inspect the following areas for vacuum leaks:
- Vacuum leaks between the Intake manifold plenum and the cylinder heads.
- Injector O-rings.
If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step 14. If no, go to next step.
- Test for proper fuel injector operation. Refer to the following:
- Fuel Injector Balance Test with Special Tool.
- Fuel Injector Coil Test. See FUEL SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article.
If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step 14. If no, go to next step.
- Test for proper ignition system operation. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step 14. If no, go to next step.
- Inspect/Test for the following mechanical conditions:
- Damaged accessory drive belt or pulley.
- Damaged driven accessory, generator, water pump, drive belt tensioner, etc.
- A loose or broken motor mount.
- Base engine mechanical condition.
If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step 14. If no, go to next step.
- Test for proper transaxle Torque Converter Clutch (TCC) operation. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to next step. If no, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.
- Use the scan tool in order to clear the DTCs. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step 2.
- 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 . If no, system is okay.