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Ignition System Diagnosis

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  1. If diagnostic system check has already been performed, go to next step. If diagnostic system check has not been performed, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS in appropriate SELF-DIAGNOSTICS article.
  2. Start engine. Select the Misfire Current counters on scan tool. Do any cylinders indicate an excessive amount of misfire? If yes, go to next step. If no, go to step  11.
  3. Is an entire bank of cylinders inoperative? If yes, go to step  16. If no, go to next step.
  4. Use scan tool to check for DTC P1351-P1366. If no IC circuit DTCs are set, inspect the IC circuit status. Are any IC circuit DTCs set or does the IC circuit status for any cylinder indicate anything other than okay? If yes, diagnose affected DTC(s). See appropriate SELF-DIAGNOSTICS article. If no, go to next step.
    5. NOTE: The remaining steps are to be performed on the cylinder indicating the highest level of misfire.
  5. Disconnect the coil assembly from spark plugs. Check coil assembly, boots and spark plug insulators for any visible cracks, deterioration or other damage. Check for carbon tracking or other signs of arcing. Did you find a problem? If yes, go to step  20. If no, go to next step.
  6. Using Ignition System Diagnosis Harness (J-36012-A), connect the coils to the spark plugs. Disconnect the spark plug on the affected cylinder and install Spark Tester (J-26792). Crank engine and note spark tester. If engine starts, turn engine off after inspecting the spark tester. Does a spark jump the tester gap? If yes, go to next step. If no, go to step  10.
  7. Remove spark plug on affected cylinder. Does spark plug show signs of oil or coolant entering the combustion chamber? If yes, diagnose for an engine mechanical problem. If no, go to next step.
  8. Inspect spark plug for any cracks, excessive wear, improper gap, burned electrodes, heavy deposits or fuel fouling. Did you find a problem? If yes, go to step  24. If no, go to next step.
  9. Install this spark plug in a different cylinder. Switch the 2 spark plugs. Reconnect coils to plugs using spark plug jumper wires. Using scan tool, select the Misfire Current counters. Start engine. Did the misfire follow the spark plug? If yes, go to step  24. If no, diagnose for an engine mechanical problem.
  10. Turn ignition off. Remove fuel pump fuse. Disconnect harness connector from the Ignition Control (IC) module. Connect a DVOM between the ignition control circuit for the affected cylinder and ground. Set DVOM to AC Hertz. Measure frequency on the ignition control circuit for the affected cylinder while cranking engine. Does frequency measure within 2-20 Hz? If yes, go to step  25. If no, go to step  30.
  11. Select the Misfire History counters using scan tool. Do any cylinders indicate a history of misfiring? If yes, go to next step. If no, go to step  33.
    12. NOTE: The remaining steps are to be performed on the cylinder indicating the highest level of misfire.
  12. Disconnect the coil assembly from spark plugs. Inspect coil assembly, boots and spark plug insulators for any visible cracks, deterioration or other damage. Check for any carbon tracking or other signs of arcing. Did you find a problem? If yes, go to step  20. If no, go to next step.
  13. Does the spark plug show signs of oil or coolant entering the combustion chamber? If yes, diagnose for an engine mechanical problem. If no, go to next step.
  14. Remove spark plug on affected cylinder. Inspect spark plug for any cracks, excessive wear, improper gap, burned electrodes, any heavy deposits or fuel fouling. Did you find a problem? If yes, go to step  24. If no, go to next step.
  15. Check resistance of affected spark plugs. Does resistance measure less than 15,000 ohms. If yes, diagnose for an engine mechanical problem. If no, go to step  24.
  16. Turn ignition off. Disconnect ignition control module for the affected cylinders. Turn ignition on. Using a test light connected to ground, probe the ignition feed circuit in the ignition control module harness. Does the test light illuminate? If yes, go to next step. If no, go to step  21.
  17. Connect test light between the ignition feed circuit and ground circuit in the ignition control module harness. Does the test light illuminate? If yes, go to next step. If no, go to step  22.
  18. Using a DVOM, measure resistance between the ground circuit and reference low circuit in the harness connector of the ignition control module. Does resistance measure less than or equal to 5 ohms. If yes, go to next step. If no, go to step  23.
  19. Turn ignition off. Remove fuel pump fuse (located in underhood fuse block). Disconnect ignition control module harness connector. Connect a DVOM between the IC circuit of one of the affected cylinders and ground. Set DVOM to AC Hertz. Measure the frequency while cranking engine. Repeat test on each IC circuit. Does frequency measure within 2-20 Hz. If yes, go to step  25. If no, go to step  30.
  20. Perform any repairs as necessary. Did you complete the repairs? If yes, go to step  31. If no, go to step  33.
  21. Repair open or high resistance in ignition 1 voltage circuit. Did you complete the repair? If yes, go to step  31. If no, go to step  33.
  22. Repair open or high resistance in the ground circuit. Did you complete the repair? If yes, go to step  31. If no, go to step  33.
  23. Repair open or high resistance in the low reference circuit. Did you complete the repair? If yes, go to step  31. If no, go to step  33.
  24. Replace spark plugs as necessary. Did you complete the replacement? If yes, go to step  31. If no, go to step  33.
  25. Turn ignition off. Remove fuel pump fuse before proceeding. Remove ignition control module from ignition coil assembly. If mating connector between the module and coils came off with the module, remove the mating connector and install the connector into the coil assembly. Reconnect ignition control module to engine harness. Connect the Ignition Module Tester (J-43298) to ignition control module. Crank engine while observing tester. Does the 3 LEDs flash on and off as engine is cranked? If yes, go to next step. If no, go to step  28.
  26. Inspect for poor connections or terminal tension between the IC module and coil assembly. Did you find and correct the condition? If yes, go to step  31. If no, go to next step.
  27. Replace the affected coil assembly. After replacing coil assembly, go to step  31.
  28. Inspect for poor connections or terminal tension at IC module. Was a problem found and corrected? If yes, go to step  31. If no, go to next step.
  29. Replace ignition control module. After replacing module, go to step  31.
  30. Replace PCM. After replacing PCM, go to next step.
  31. Start engine. Select the Misfire Current counters on scan tool. Do any cylinders indicate an excessive amount of misfire? If yes, go to next step. If no, go to step  33.
  32. Is misfire indicated on the same cylinders that were just diagnosed? If yes, diagnose engine mechanical problem. If no, go to step  3.
  33. Using scan tool, clear DTCs. Operate vehicle. Does scan tool indicate that this test passed? If yes, go to next step. If no, go to step  2.
  34. Using scan tool, select the Capture Info option and Review Info option. Does scan tool display any DTCs that you have not diagnosed? If yes, diagnose affected DTC(s). See appropriate SELF-DIAGNOSTICS article. If no, system is okay.
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