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Electronic Ignition System Diagnosis

NOTE: For terminal and circuit identification, see WIRING DIAGRAMS  . For intermittent conditions, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.0L SATURN "L" SERIES article.
NOTE: Electronic Ignition Module may also be referred to as an Ignition Control Module.
NOTE: TBI Harness Test Light (J-34730-405) is required to perform this procedure. See Figure .

The ignition system uses a electronic ignition module for each bank. The electronic ignition modules consist of a controller and ignition coils. The electronic ignition modules are mounted in the center of each camshaft cover with short boots connecting the coils to the spark plugs. The Engine Control Module (ECM) primarily uses engine speed and position information from the Crankshaft Position (CKP) and Camshaft Position (CMP) sensors to control the sequence, dwell, and timing of the spark. The ECM can command each ignition coil ON/OFF by grounding the control circuit of the ignition coil. The control circuits are Pulse Width Modulated (PWM) in order to precisely control the spark events.

  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 under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.0L SATURN "L" SERIES article.
  2. Attempt to start the engine. If the engine starts and idles, go to next step. If engine does not start and idle, go to step  4 .
  3. Idle the engine. Monitor the misfire counters with a scan tool. If the misfire counters indicate misfires for one cylinder, go to step  8 . If misfire counters do not indicate misfires for one cylinder, go to next step.
  4. Turn ignition off. Disconnect the harness connector of the inoperative electronic ignition module. Turn ignition on, with engine off. Connect a test light from the electronic ignition module ignition voltage circuit to a good ground. If the test light illuminates, go to next step. If test light does not illuminate, go to step  15 .
  5. Connect a test light from the ignition voltage circuit to the ground circuit of the electronic ignition module. If the test light illuminates, go to next step. If test light does not illuminate, go to step  16 .
  6. Remove the IGN fuse in the underhood fuse block. Measure the resistance of the electronic ignition module ignition voltage circuit from the IGN fuse in the underhood fuse block to the electronic ignition module harness connector with a DVOM. If the resistance is less than 3 ohms, go to next step. If resistance is more than 3 ohms, go to step  17 .
  7. Measure the resistance of the electronic ignition module ground circuit from the harness connector of the electronic ignition module to a good ground with a DVOM. If the resistance is less than 3 ohms, go to step  13 . If resistance is more than 3 ohms, go to step  18 .
    8. NOTE: If using a different test light, the bulb resistance needs to be 4 ohms or less.
  8. Disconnect the harness connector of the electronic ignition module. Using jumper wires, connect the TBI Harness Test Light from the ignition voltage circuit to the control circuit of the inoperative ignition coil in the electronic ignition module harness connector. Command the inoperative ignition coil ON with a scan tool. If the TBI Harness Test Light flashes, go to step  10 . If TBI Harness Test Light does not flash, go to next step.
  9. If the TBI Harness Test Light remains on, go to step  11 . If the TBI Harness Test Light does not remain on, go to step  12 .
  10. Using jumper wires, connect the TBI Harness Test Light from the ignition voltage circuit to the control circuit of the good ignition coil in the electronic ignition module harness connector. Command the ignition coil ON with a scan tool. Compare the illumination of the good coil to that of the inoperative coil. If the TBI Harness Test Light illuminates with same brightness for both circuits, go to step  13 . If illumination brightness is not the same, go to step  12 .
  11. Test the control circuit of the inoperative ignition coil for a short to ground. Did you find and correct a short to ground? If yes, go to step  21 . If no, go to step  14 .
  12. Test the control circuit of the inoperative ignition coil for an open, a short to voltage or high resistance of more than 3 ohms. Did you find and correct an open, a short to voltage or high resistance of more than 3 ohms? If yes, go to step  21 . If no, go to step  14 .
  13. Test for shorted terminals or a poor connection at the electronic ignition module. Did you find and correct any shorted terminals or poor connections? If yes, go to step  21 . If no, go to step  19 .
  14. Test for shorted terminals or a poor connection at the Engine Control Module (ECM). Did you find and correct any shorted terminals or poor connections? If yes, go to step  21 . If no, go to step  20 .
  15. Repair an open or a short to ground in the ignition voltage circuit of the electronic ignition module. After repair is complete, go to step  21 .
  16. Repair an open in the ground circuit of the electronic ignition module. After repair is complete, go to step  21 .
  17. Repair the high resistance in the ignition voltage circuit of the electronic ignition module. After repair is complete, go to step  21 .
  18. Repair the high resistance in the ground circuit of the electronic ignition module. After repair is complete, go to step  21 .
  19. Replace the electronic ignition module. See ELECTRONIC IGNITION MODULE under IGNITION SYSTEMS in REMOVAL & INSTALLATION - SATURN "L" SERIES article. After replacement is complete, go to step  21 .
  20. Replace the ECM. ENGINE CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION - SATURN "L" SERIES article. After replacement is complete, go to next step.
  21. Turn the ignition off for 30 seconds. Start the engine and operate the vehicle. Observe the vehicle performance and driveability. If the vehicle operates normally, system is okay. If vehicle does not operate normally, go to step  2 .
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