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

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Special Tools

J 26792 HEI Spark Tester

Observe the Engine Controls Schematic for the ignition coils/modules, and review the Ignition System Specifications to verify the following:

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

1. Turn OFF the ignition.
2. Inspect the fuse that supplies voltage to the ignition coil/modules.

⇒	If the fuse is open, then test the spliced circuits and the individual ignition coil/modules for a short to ground.

3. Disconnect the affected ignition coil/module.
4. Connect a test lamp between the ignition coil/module ignition 1 voltage circuit terminal A and a good ground.
5. Turn ON the ignition.
6. With the test lamp still connected, measure for battery voltage between the ignition 1 voltage circuit and a good ground.

⇒	If the voltage is not within 1 volt of battery voltage, repair the high resistance or the open in the ignition 1 voltage circuit.

7. 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.
8. Measure for a proper value of less than 5 ohms between the ground circuit terminal D of the affected ignition coil/module and a good ground.

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

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

⇒	If the misfire transfers with the suspect ignition coil/module, replace as needed.

⇒	If the misfire does not transfer with the suspect ignition coil/module, observe the component testing procedures below, and replace the spark plug if needed.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.