Ignition System: Testing and Inspection

ELECTRONIC IGNITION (EI) SYSTEM DIAGNOSIS

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

The ECM 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 ECM can determine when a cylinder is on either the firing or the exhaust stroke by the 24X signal.

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

For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections. Component Tests and General Diagnostics

TEST DESCRIPTION

Step 1 - Step 12:

Step 13 - Step 24:

Step 25 - Step 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 1 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.