Ignition System: Testing and Inspection

CIRCUIT DESCRIPTION
The ignition control (IC) module and powertrain control module (PCM) use the low resolution engine speed signal to control ignition operation. The low resolution engine speed signal is derived from the crankshaft position (CKP) sensor, which is connected directly to the IC module. The IC module has independent power and ground circuits. The circuits between the IC module and the PCM consist of the following:
- The low reference circuit
- The low resolution engine speed signal circuit
- The IC timing control circuit
- The IC timing control B circuit

DIAGNOSTIC AIDS
- A small amount of resistance in the battery positive voltage to the PCM may cause a no start. Refer to Diagnostic Aids for Circuit Testing and Wiring Repair Procedures.
- The PCM grounds will cause a no start only if none of them are making a good connection. Refer to Diagnostic Aids for Circuit Testing and Wiring Repair Procedures.
- A loose CKP sensor may cause an intermittent no start by moving away from the reluctor wheel.

TEST DESCRIPTION

Steps 1-4:

Steps 5-8:

Steps 9-12:

Steps 13-16:

Steps 17-19:

Steps 20-27:

Steps 28-31:

The number below refers to the step number on the diagnostic table.
7. Inspect for basic engine malfunctions, such as low compression, burnt valves, a worn timing chain and worn gears, etc.