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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 83 (Engine Controls Self-Diagnostics - 2.2L) >> Diagnostic Tests >> DTC P0301-P0304: Cylinder Misfire Detected >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 GMC Sonoma and 2002 Chevrolet S10 Pickup. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
  2. Are any component DTCs set? If yes, diagnose affected DTCs first. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no other DTCs are set, go to next step.
  3. Perform a visual and physical inspection. Make any necessary repairs. Were any repairs necessary? If yes, go to step  6. If no, go to next step.
  4. With engine idling, install scan tool. Observe scan tool. If misfire current counter is incrementing on the cylinder that had a misfire DTC, go to next step. If misfire current counter is not incrementing on the cylinder that had a misfire DTC, go to step  6.
  5. Turn ignition off. Disconnect fuel injector harness connector. Install Spark Tester (J-26792) to misfiring cylinder spark plug wire. Remove spark plug wire from ignition coil. Connect a jumper wire between ground and the misfiring cylinder pair ignition coil tower. Crank engine and check for spark. If spark is present, go to step  8. If spark is not present, go to step  9.
  6. Turn ignition on, with engine off. Review the Freeze Frame data and note parameters. Operate vehicle within the Freeze Frame conditions and Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . Is the misfire current counter incrementing on the cylinder that indicated a misfire? If yes, go to step  5. If no, go to next step.
  7. Was a repair made from the visual and physical inspection? If yes, go to step  30. If no, see DIAGNOSTIC AIDS .
  8. Remove spark plug from misfiring cylinder. Replace spark plug with a known-good spark plug. Reconnect fuel injection harness connector. Operate vehicle within misfire conditions as recorded in FREEZE FRAME. Is the misfire current counter incrementing on the cylinder that indicated a misfire? If yes, go to step  13. If no, go to step  22.
  9. Remove spark plug wire from misfiring cylinder. Using DVOM, check plug wire resistance. Is resistance less than 1000 ohms per inch? If yes, go to next step. If no, go to step  23.
  10. Remove ignition coil from cylinder that did not have spark. Check secondary resistance of coil. Is resistance 5000-8000 ohms? If yes, go to next step. If no, go to step  24.
  11. Replace ignition coil with a known-good coil. Crank engine and check for spark. If spark is present, go to step  24. If spark is not present, go to next step.
  12. Disconnect and Check Ignition Control Module (ICM) 6-pin connector. Repair as necessary. After repairs, go to step  30. If connector is okay, go to step  25.
  13. Turn ignition off. Disconnect all fuel injector connectors. Install injector test light on injector harness connector for misfiring cylinder. Crank engine and observe test light. If test light flashes, go to next step. If test light does not flash, go to step  15.
  14. Perform INJECTOR BALANCE TEST. See FUEL SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. Is the fuel injector okay for the cylinder that had indicated a misfire? If yes, go to step  28. If no, go to step  29.
  15. Remove injector test light. Connect a test light between ground and ignition feed terminal at affected injector harness connector. Crank engine and observe test light. Did the test light illuminate? If yes, go to next step. If no, go to step  27.
  16. Connect test light to ground. Disconnect fuel injector harness connectors. Turn ignition on, with engine off. Probe fuel injector harness connector control circuit terminal for cylinder that indicated a misfire. If test light remains off, go to next step. If test light does not remain off, go to step  26.
  17. With test light connected to positive battery terminal, probe injector control circuit terminal at injector harness connector. If test light is off, go to next step. If test light is on, go to step  19.
  18. Check PCM connectors for damaged pins, corrosion and loose wires. If connectors are okay, go to step  20. If connectors are not okay, go to step  21.
  19. Check for short to ground in fuel injector control circuit for misfiring cylinder. Repair as necessary. After repairs, go to step  30. If circuit is okay, go to next step.
  20. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to step  30.
  21. Repair connector or connections as necessary. After repairs, go to step  30.
  22. Replace spark plug. After replacing spark plug, go to step  30.
  23. Replace spark plug wire. After replacing spark plug wire, go to step  30.
  24. Replace ignition coil. After replacing ignition coil, go to step  30.
  25. Replace ICM module. After replacing module, go to step  30.
  26. Check for short to voltage in misfiring cylinder fuel injector control circuit. Repair as necessary. After repairs, go to step  30. If circuit is okay, go to step  20.
  27. Repair open in ignition feed circuit. After repairs, go to step  30.
  28. Check for a basic engine problem (compression, cam timing, throttle body leak, restricted airflow, etc.). Repair as necessary. After repairs, go to step  30.
  29. Replace defective fuel injector. After replacing fuel injector, go to next step.
  30. Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start engine. Operate the 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  2.
  31. 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.
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