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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 102 (Engine Controls - Self-Diagnostics - 3.5L) >> Diagnostic Tests >> DTC P0300-P0306: Engine Misfire Detected >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Oldsmobile Intrigue and 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.
  1. 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.
  2. Incorrect CKP system variation data in PCM may cause DTC to set with no apparent misfire. Any of the following conditions can cause incorrect CKP system variation data:
    • Replacing engine.
    • Replacing PCM.
    • Reprogramming PCM.
    • Replacing CKP sensor.
    • Performing internal engine repairs that affect CKP sensor-to-crankshaft reluctor wheel relationship.

    If none of the listed conditions apply to vehicle, go to next step. If any of the listed conditions apply to vehicle, CKP system variation learn procedure must be performed before continuing with misfire diagnosis. See CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE  under PROGRAMMING.

  3. Are any other DTCs are set? If yes, diagnose affected DTC(s). See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  4. Start engine. Using scan tool, select MISFIRE BAR GRAPH or MISFIRE COUNTERS. If any cylinders indicate excessive misfire, go to next step. If no cylinders indicate excessive misfire, see DIAGNOSTIC AIDS .
  5. If misfire seems to be affecting specific cylinders, go to step  14. If misfire is random to all cylinders, go to next step.
  6. Inspect the vacuum hoses for splits, for kinks, and for incorrect connections. Did you find and correct the condition? If yes, go to step  19. If no, go to next step.
  7. Inspect PCV valve for incorrect installation and for any damaged O-rings. Did you find and correct the condition? If yes, go to step  19. If no, go to next step.
  8. Inspect throttle body inlet and duct work for damage and for objects that may alter the air flow through the MAF sensor. Did you find and correct the condition? If yes, go to step  19. If no, go to next step.
  9. Check fuel pressure. Did you find and correct the condition? If yes, go to step  19. If no, go to next step.
  10. Check fuel for excess water, alcohol, and for other contaminants. Did you find and correct the condition? If yes, go to step  19. If no, go to next step.
  11. Ensure PCM grounds and Ignition Control Module (ICM) grounds are clean, tight, and in the correct locations. Did you find and correct the condition? If yes, go to step  19. If no, go to next step.
  12. Inspect for any vacuum leaks at the intake manifold, EGR adapter, EGR valve, EGR feed pipes or fuel injector O-rings. Did you find and correct the condition? If yes, go to step  19. If no, go to next step.
  13. Remove EGR valve. Verify that the pintle is not partially stuck open. Inspect EGR valve pintle and seat for carbon deposits and burrs that may interfere with the pintle closing completely. Did you find and correct the condition? If yes, go to step  19. If no, go to next step.
  14. Check for correct ignition system operation. Did you find and correct the condition? If yes, go to step  19. If no, go to next step.
  15. Check for correct fuel injector operation. Use Tech 2 scan tool to perform Fuel Injector Balance Test. Did you find and correct the condition? If yes, go to step  19. If no, go to next step.
  16. Check for vacuum leaks that may affect one cylinder more than other cylinders. Leaks can be caused by fuel injector O-rings or any intake manifold leak. Did you find and correct the condition? If yes, go to step  19. If no, go to next step.
  17. Check for damaged accessory drive belt, damaged pulley or a damaged belt-driven accessory. Check for any engine mechanical problem or a loose or is broken motor mount. Did you find and correct the condition? If yes, go to step  19. If no, go to next step.
  18. Check transaxle Torque Converter Clutch (TCC). See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If a condition is found, repair transaxle as necessary. Did you find and correct the condition? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  19. Using scan tool, clear DTCs. Turn the ignition OFF for 30 seconds. Start engine. Operate vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, go to step  3.
  20. Using scan tool, check for any other DTCs that are set. If no other DTCs are set, system is okay. If any other DTCs are set, repair DTCs as necessary. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
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