Ignition System: Testing and Inspection

Electronic Ignition (EI) System Diagnosis

Refer to Ignition Coils, Bank 1 in Engine Controls Schematics.

Circuit Description

A crankshaft position (CKP) sensor determines the engine crankshaft position. The sensor is mounted and protrudes into the engine front cover. The sensor is near a slotted reluctor ring on the crankshaft. The rotation of the slotted reluctor ring causes a magnetic flux change in the sensor. This produces a voltage signal from the electronic ignition control module (ICM). The signal creates the reference pulses needed by the powertrain control module (PCM). These signals trigger the correct ignition coil to fire, at the correct time.

The ignition system on this engine uses an individual ignition coil/module for each cylinder. The PCM controls the ignition system operation. There are 8 IC circuits, 1 per cylinder, that connect the PCM and the ignition coil/modules. Each ignition coil/module has an ignition positive voltage circuit, a ground circuit, and a reference low circuit. The PCM causes a spark to occur by grounding the IC circuit, which signals the ignition module to trigger the ignition coil and fire the spark plug. The PCM controls the sequencing and timing.

Diagnostic Aids

* Inspect for the following conditions that may cause intermittents:

- Poor connections
- Inadequate terminal tension
- Corrosion
- Misrouted harness
- Rubbed through wire insulation
- Broken wire inside the insulation
Refer to Wiring Repairs Wiring Repairs in Wiring Systems.

* Inspect for further causes of intermittent conditions, refer to Symptoms Symptoms.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

Important: Be sure to use the same diagnostic equipment for all measurements.


2. This step will identify the misfiring cylinders. The spark tester requires a minimum of 25,000 volts to operate. It may be necessary to use the spark tester on all of the cylinders because the ignition system may provide enough voltage to run the engine but not enough to operate a spark plug under a heavy load. If you were sent here from the Engine Cranks But Will Not Run table, check for a faulty connection at the engine ground terminal.
10. This step determines if the malfunction is affecting one cylinder or an entire bank of the ignition system.
15. This test checks for a short to voltage at the ignition control (IC) signal circuit between the ignition coil/module and the PCM.
16. This test will determine which side of the 8-way connector the malfunction is located.
17. This test checks for a short to ground at the ignition control (IC) signal circuit between the PCM connector and the 8-way connector.
22. This step completes the testing of the ignition system for a problem that will cause an entire bank to malfunction.