Diagnostic Instructions
Circuit/System Description
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:
• | An ignition voltage circuit |
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Special Tools
J 26792
HEI Spark Tester
Circuit/System Verification
Observe the Engine Controls Schematic for the ignition coils/modules, and review the Ignition System Specifications to verify the following:
• | The ignition coil/modules are correctly connected |
• | The proper firing order |
• | The proper spark plug type |
• | The proper spark plug gap and torque |
Circuit/System Testing
Important: Verify that the engine is in good mechanical condition before continuing with this diagnosis.
- Turn the ignition OFF.
- Inspect the fuse that supplies voltage to the ignition coil/modules.
⇒ | If the fuse is open, test the spliced circuits and the individual ignition coil/modules for a short to ground. |
- Disconnect the affected ignition coil/module.
- Connect a test lamp between the ignition coil/module ignition 1 voltage circuit and a good ground.
- With the test lamp still connected, measure for battery voltage between the ignition 1 voltage circuit and a good ground.
⇒ | If the voltage is within 0.5 V of battery voltage, repair the high resistance or the open in the ignition 1 voltage circuit. |
- 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.
- Measure for less than 5 ohms of a proper value between the ground circuit 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. |
- Change the affected ignition coil/module with the ignition/coil module of a good cylinder.
- Start the engine, and observe the scan tool.
⇒ | If the misfire occurs with the suspect ignition coil/module, replace as needed. |
⇒ | If the misfire does not occur with the suspected ignition coil/module, observe the component testing procedures below, replace the spark plugs as needed. |
Component Testing
• | Use the Spark Plug Inspection procedure to verify the integrity of the spark plugs. Refer to
Spark Plug Inspection
. |
• | Verify the output of each ignition coil/module using the
J 26792
. |
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.