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Electronic Ignition System Diagnosis

Electronic Ignition System Diagnosis

Diagnostic Instructions


• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• Diagnostic Procedure Instructions provides an overview of each diagnostic category.


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 circuit of each ignition coil/module to enable a spark event.

Diagnostic Aids


• Depending on location in the spliced ignition voltage circuit, a slight resistance can cause a misfire or a crank/no start concern. A voltage drop test will pinpoint this condition.

• A slight to moderate resistance on any ignition control circuit can cause a misfire before DTC P0351-P0354 sets.

• Extended engine cranking time, may foul the spark plugs with excessive fuel.


Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference


• Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs


Scan Tool Reference

Control Module References for scan tool information

Special Tools

J 26792 HEI Spark Tester

Circuit/System Testing


1. Ignition OFF, disconnect the harness connector at the affected T8 ignition coil/modules.

2. Ignition OFF, all vehicle systems OFF. This may take up to 2 minutes. Test for less than 5 Ω between the ground circuit terminal A/1 and ground.

3. If greater than the specified range, test the ground circuit for an open/high resistance.

4. Test for less than 5 Ω between the low reference circuit terminal B/2 and ground.

5. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.

6. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal D/4 and ground.

7. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.

8. Exchange the affected T8 ignition coil/module with the T8 ignition coil/module of a good cylinder.

9. Start the engine, and observe the scan tool Misfire Current Cylinder parameters.

10. If the misfire transfers with the suspect T8 ignition coil/module, replace as needed.

11. If the circuits test normal, test or replace the spark plug/s.


Component Testing

Use the J 26792 Spark Tester to verify the output of each ignition coil/module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


• Ignition Coil Replacement

• Spark Plug Replacement