Electronic Ignition (EI) System Diagnosis

ELECTRONIC IGNITION (EI) SYSTEM DIAGNOSIS

CIRCUIT DESCRIPTION
The electronic ignition system uses an individual ignition coil for each cylinder. The powertrain control module (PCM) controls the ignition operation through eight individual ignition control (IC) circuits. Each bank of four ignition coils is connected to the PCM, power, or ground by the following circuits:
- Low reference
- Chassis ground
- Ignition 1 voltage
- The appropriate IC circuit

The PCM triggers an ignition coil by grounding the appropriate IC circuit using information from the crankshaft position (CKP) and camshaft position (CMP) sensors.

DIAGNOSTIC AIDS

IMPORTANT: A missing CMP sensor signal may cause a long crank condition.

The CKP signal must be available for the engine to start. The CMP signal is not needed to start and operate the engine. The PCM can determine when a cylinder is on either the firing or exhaust stroke by the 24X signal.

Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.

For an intermittent condition, refer to Intermittent Conditions. Intermittent Conditions

TEST DESCRIPTION

Steps 1 - 12:

Steps 13 - 24:

Steps 25 - 36:

The numbers below refer to the step numbers on the diagnostic table.
5. Monitoring the misfire current counters determines if a fault is present.
12. A good indication that the fuse is open is all off the misfire current counters are incrementing on one side of the engine. Inspect the ignition positive voltage circuit for a grounded circuit. If the fuse is open and the ignition coil circuits are OK, inspect the injector circuits for being grounded.