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Home >> Saturn >> 2003 >> Ion 1 Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0300: Engine Misfire Detected >> Diagnostic Procedures

Diagnostic Procedures

  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. NOTE: You MUST perform the Crankshaft Position (CKP) system variation learn procedure before proceeding with this diagnostic procedure. Go to CKP SYSTEM VARIATION LEARN PROCEDURE  under PROGRAMMING.
  2. Start engine. Allow engine to idle or operate within the conditions listed in the Freeze Frame/Failure Records. Monitor all of the Misfire counters using the scan tool. Are any of the Misfire Current counters incrementing? If yes, go to next step. If no, refer to INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 2.2L ION article.
  3. Are any DTCs other than P0340 or P0341 set? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  4. Can any abnormal engine noise be heard? If yes, diagnose engine mechanical problem. See appropriate article in ENGINES. If no, go to next step.
  5. Observe the Misfire History Cyl# parameter with a scan tool. Does more than one cylinder indicate a large count value for the Misfire History Cyl# parameter? If yes, go to next step. If no, go to step  8.
  6. Are the Misfire History Cyl# counts indicated for companion cylinders 1/4 or 2/3? If yes, go to step  8. If no, go to next step.
  7. Inspect vacuum hoses and seals for splits, restrictions, and improper connections. Inspect crankcase ventilation system for vacuum leaks, ECM grounds for corrosion and loose connections, exhaust system for restrictions, or fuel for contamination. Did you find and correct the condition? If yes, go to step  17. If no, go to next step.
  8. Turn OFF the ignition. Remove the fuel pump relay. Remove the ignition coil housing assembly, keeping the Ignition Control (IC) module assembly connected to the harness connector. Connect a jumper wire between the top of the IC module and a good ground. Install Ignition System Diagnosis Harness (J 36012-A). Install a Spark Tester (J 26792) on the No. 1 spark plug jumper wire. Ground the No. 4 spark plug jumper wire. The No. 4 wire is the companion to No. 1. Crank engine with the remaining spark plug wires connected. Repeat steps by installing the spark tester on No. 4 and grounding No. 1. Do the same for the No. 2 and No. 3 spark plugs. Ensure the companion wire is grounded. Does the spark tester spark on all cylinders? If yes, go to next step. If no, diagnose Electronic Ignition (EI) System. Refer to IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L ION article.
  9. Remove spark plug from the cylinder that indicated a misfire. Inspect the spark plug. Does the spark plug appear to be okay? If yes, go to next step. If no, go to step  11.
  10. Exchange the suspected spark plug with another cylinder that is operating properly. Operate the vehicle under the same conditions that the misfire occurred. Did the misfire move with the spark plug? If yes, go to step  17. If no, go to step  14.
  11. Is the spark plug oil or coolant fouled? If yes, diagnose for an engine mechanical problem. If no, go to next step.
  12. Is the spark plug gas fouled? If yes, go to step  15. If no, go to next step.
  13. Did the spark plug show any signs of being cracked, worn, or improperly gapped? If yes, go to step  16. If no, go to step  14.
  14. Perform the fuel injector coil test. Refer to FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 2.2L ION article. Did you find and correct the condition? If yes, go to step  18. If no, diagnose for an engine mechanical problem.
  15. Perform the fuel system diagnosis. Refer to FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 2.2L ION article. Did you find and correct the condition? If yes, go to step  18. If no, diagnose for an engine mechanical problem.
  16. Replace or gap the spark plug. After replacement, go to step  18.
  17. Replace faulty spark plug. After replacing spark plugs, go to next step.
  18. Was the customer's concern with the MIL flashing? If yes, go to next step. If no, go to step  20.
  19. Operate the vehicle at 2500 RPM for 4 minutes. Operate the vehicle within the Conditions for Running the DTC in DTC P0420. See CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, go to DTC P0420: CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD - BANK 1 .
  20. Using a scan tool, clear the DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? If yes, go to step  2. If no, go to next step.
  21. Using a scan tool, observe the 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 at this time.
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