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Ignition System Diagnosis

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  1. If spark is not present at a specific cylinder, go to next step. If spark is not present on all cylinders on a specific ignition coil, go to step  4. If spark is not present at all, go to step  6.
  2. Disconnect appropriate ignition control module harness connector. Connect test light between battery positive terminal and ignition coil control circuit in question. Using scan tool, command appropriate ignition coil on. If test light does not illuminate, go to next step. If test light flashes, terminal connections or ignition control module is faulty. If test light remains illuminated, ignition coil control circuit is shorted to ground, or ECM is faulty.
  3. Connect test light between ground and ignition coil control circuit in question. If test light illuminates, control circuit is shorted to voltage. If test light does not illuminate, control circuit is open, or terminal connections or ECM is faulty.
  4. Turn ignition off. Disconnect appropriate ignition control module harness connector. Turn ignition on. Connect test light between ignition control module ignition feed circuit and ignition control module ground circuit at ignition control module harness connector. If test light illuminates, go to next step. If test light does not illuminate, repair open in ignition feed circuit.
  5. Connect test light between engine ground circuit at ignition control module harness connector and battery positive terminal. If test light illuminates, terminal connections or ignition control module are faulty. If test light does not illuminate, repair open in engine ground circuit.
  6. Engine ground circuit or IGN fuse (15-amp) is faulty. If fuse is at fault and continues to blow, an ignition control module is shorted to ground. Repair as necessary.
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