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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 103 (Engine Controls Self-Diagnostics - 2.2L) >> Diagnostic Tests >> DTC P0300: Engine Misfire Detected (SOHC) >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Pontiac Sunfire, 2002 Pontiac Grand Am, 2002 Oldsmobile Alero, and 2002 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Before clearing DTCs, record FREEZE FRAME/FAILURE RECORDS for reference with a scan tool. This data will be lost when you use CLEAR DTC information function.
  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
  2. Are any other DTCs set? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  3. Start engine. Monitor the Misfire current parameter in the misfire data list with a load on the engine. Refer to Freeze Frame data. Is the Misfire counter increasing? If yes, go to step  5. If no, go to next step.
  4. Turn engine off. Use a spray bottle filled with water in order to wet down the secondary ignition system. Start engine. Monitor the misfire current parameter in the misfire data list with a load on the engine. Does the scan tool indicate a misfire is present? If yes, go to next step. If no, go to step  18.
  5. Is the misfire random on all cylinders? If yes, go to step  10. If no, go to next step.
  6. Is the misfire consistent on specific cylinders? If yes, go to next step.
  7. Turn ignition off. Connect the spark tester to the spark plug wires of the cylinders indicating a misfire. Start and idle the engine. Does the tester indicate spark is consistent on all tested spark plug wires? If yes, go to next step. If no, go to step  9.
  8. Remove the spark plugs from the cylinders that indicate a misfire. Inspect the spark plugs. Did you find a problem? If yes, go to step  17. If no, go to next step.
  9. Install the spark plugs in the cylinders that were not indicating a misfire. Start engine. Monitor the Misfire current parameter in the misfire data list. Did the misfires change cylinders? If yes, go to step  15. If no, go to step  11.
  10. Perform the fuel system diagnostic. Repair as necessary. Did you find a problem? If yes, go to step  18. If no, go to step  16.
  11. Perform the Fuel Injector Balance Test. Did you find a problem? If yes, go to next step. If no, go to step  17.
  12. Connect the J-34730-405 Injector Test light on the injector harness connector, on the PCM side. Crank the engine. Does the injector test light flash for each injector? If yes, go to step  14. If no, go to next step.
  13. Inspect the injector harness for a short to voltage between the PCM connector and the injector connector that failed the Balance Test using a DMM. Is the voltage greater than 0-1 volt? If yes, go to next step. If no, go to step  16.
  14. Repair short to voltage on the injector control circuit. After repairs, go to step  19.
  15. Replace spark plugs. When complete, go to step  19.
  16. Physically and visually check for contaminated fuel, fouled or damaged spark plugs, faulty ignition coil and connections, restricted exhaust system or faulty PCM grounds. Repair as necessary. Did you find a problem? If yes, go to step  19. If no, go to next step.
  17. Inspect for engine mechanical problems. Repair as necessary. Did you find a problem? If yes, go to step  19. If no, go to DIAGNOSTIC AIDS .
  18. Perform the Crankshaft Position (CKP) variation learn procedure. See CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE  under PROGRAMMING. When complete, go to next step.
  19. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running the DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  20. 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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