Ignition System: Testing and Inspection

Electronic Ignition (EI) System Diagnosis

Diagnostic Fault Information

Important: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Diagnostic System Check - Vehicle

Circuit/System Description

The ignition system uses individual ignition coil assemblies for each cylinder. The powertrain control module (PCM) controls each individual ignition coil by transmitting timing pulses on the ignition control (IC) circuit of each ignition coil to enable a spark event. Each ignition coil has the following circuits:

* An ignition voltage circuit
* A ground circuit
* An IC control circuit

Circuit/System Verification

Observe the Engine Controls schematic for the ignition coils, and review the ignition system specifications to verify the following:

* The ignition coils are correctly connected
* The proper firing order
* The proper spark plug type
* The proper spark plug gap and torque
Refer to Ignition System Specifications.

Circuit/System Testing

Important: Verify that the engine is in good mechanical condition before continuing with this diagnostic.

1. Turn ON the ignition.
2. Inspect the fuse that supplies voltage to the ignition coils.

• If the fuse is open, test the spliced circuits and the individual ignition coils for a short to ground.

3. Disconnect the affected ignition coil.
4. Connect a test lamp between the ignition voltage circuit and a good ground.
5. With the test lamp still connected, measure for battery voltage between the ignition voltage circuit and a good ground.

• If the voltage is not within 0.5 volt of battery voltage, repair the high resistance or the open in the ignition voltage circuit.

6. Turn OFF the ignition, and all electrical accessories. Allow sufficient time for all of the control modules to power down before taking a resistance measurement.
7. Measure for a proper value of less than 5 ohms of resistance between the ground circuit of the affected ignition coil and a good ground.

• If the resistance is more than 5 ohms, repair the high resistance or the open in the ground circuit.

8. Exchange the affected ignition coil with the ignition coil of a good cylinder.
9. Start the engine and observe the scan tool.

• If the misfire transfers with the suspect ignition coil, replace as needed.
• If the misfire does not transfer with the suspect ignition coil, review the component testing procedures below and replace the spark plug, if needed.

Component Testing

* Use the Spark Plug Inspection procedure to verify the integrity of the spark plugs. Refer to Spark Plug Inspection. Testing and Inspection
* Use the J26792 to verify the output of each ignition coil.

Repair Instructions

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Spark Plug Replacement.
* Ignition Coil Replacement.