Electronic Ignition (EI) System Diagnosis

Electronic Ignition System Diagnosis

Diagnostic Instructions

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

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

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

Circuit/System Description

This ignition system uses individual ignition coil assemblies for each cylinder. The engine control module (ECM) controls the spark events by transmitting the timing pulses on the ignition control (IC) circuits to the individual ignition module/coil assemblies in firing order sequence. Each ignition module/coil has the following circuits:

* An ignition 1 voltage circuit

* A ground circuit

* An IC circuit

* A low reference circuit

Diagnostic Aids

* An open/high resistance on the low reference circuit to the ignition coil may cause a misfire.

* An erratic or weak spark is considered a no spark condition.

Reference Information

Schematic Reference

Engine Controls Schematics [1][2]Electrical Diagrams

Connector End View Reference

Component Connector End Views Outside Rearview Mirror - Driver

Description and Operation

Electronic Ignition System Description Description and Operation

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Control Module References

Special Tools

EL 26792 - HEI Spark Tester

For equivalent regional tools, refer to Special Tools Tools and Equipment.

Circuit/System Testing

Note: Do not perform this diagnostic procedure unless you were sent here from a misfire DTC or the Engine Cranks But Does Not Run diagnostic.

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the appropriate T8 Ignition Coil. It may take up to 2 minutes for all vehicle systems to power down.

2. Test for less than 5 ohms between the ground circuit terminal A and ground.

• If 5 ohms or greater

1. Ignition OFF.

2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, repair the open/high resistance in the ground connection.

• If less than 5 ohms

3. Test for less than 5 ohms between the low reference circuit terminal B and ground.

• If 5 ohms or greater

1. Ignition OFF, disconnect the X3 harness connector at the K20 Engine Control Module.

2. Test for less than 2 ohms in the low reference circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K20 Engine Control Module.

• If less than 5 ohms

4. Ignition ON.

5. Test for 11-16 V between the ignition voltage circuit terminal D and ground.

• If not between 11-16 V
Repair the open/high resistance in the circuit.

• If between 11-16 V

6. Ignition OFF, disconnect the X3 harness connector at the K20 Engine Control Module.

7. Test for infinite resistance between the harness connector at the T8 Ignition Coil control circuit terminal C and ground.

• If less than infinite resistance
Repair the short to ground on the circuit.

• If infinite resistance

8. Ignition OFF, exchange the suspect T8 Ignition Coil with the T8 Ignition Coil of a known functioning cylinder.

9. Engine running.

10. Verify the scan tool Ignition Coil Control Circuit Status parameter displays OK for the same cylinder that the suspect T8 Ignition Coil was removed from.

• If OK is not displayed
Replace the K20 Engine Control Module.

• If OK is displayed
Test or replace the suspect T8 Ignition Coil.

Component Test

Note: You must perform the Circuit/System Testing before proceeding with Component Testing.

1. Ignition OFF, connect the EL 26792 - spark tester to the appropriate T8 Ignition Coil.

2. Engine running.

3. Verify the spark output of the T8 Ignition Coil.

• If no output or the output is weak
Replace the T8 Ignition Coil.

• If the output is normal

4. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* Ignition Coil Replacement Service and Repair

* Control Module References Control Module References for engine control module replacement, programming, and setup.