Ignition System: Testing and Inspection

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

There are 3 dual-tower ignition coils that are part of the ignition control (IC) module. The IC module contains coil driver circuits that command the coils to operate. The IC module has the following circuits:

* An ignition voltage circuit
* A ground
* An ignition control (IC) 1 control circuit for the 1-4 ignition coil
* An IC 2 control circuit for the 2-5 ignition coil
* An IC 3 control circuit for the 3-6 ignition coil
* A low reference circuit

The engine control module (ECM) controls each dual-tower ignition coil by transmitting timing pulses on the ignition coil control circuit to the IC module for the proper coil to enable a spark event.

Diagnostic Aids

Inspect the spark plug wires for proper orientation.

Reference Information
Schematic Reference

Computers and Control Systems Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Electronic Ignition System Description (Description and Operation)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Programming and Relearning (Programming and Relearning) for scan tool information
Special Tools

J 26792 Spark Tester

Circuit/System Testing

1. With the ignition OFF, remove the fuel pump relay.
2. Crank the engine and test for a strong spark on each cylinder spark plug wire using the J 26792. Ground the companion cylinder spark plug wire of each cylinder when it is tested.

• If a strong bright blue spark is present on all 6 of the cylinders, remove and inspect all of the spark plugs for proper torque, proper gap, wear, damage, and fouling. Refer to Spark Plug Inspection (Testing and Inspection). Replace the spark plugs if necessary.
• If there is no spark on any of the cylinders, test the ignition voltage circuit of the IC module for an open/high resistance or short to ground, or test the ground circuit of the IC module for an open/high resistance, or a faulty IC module. The wire circuit resistance should measure less than 3 ohms.
• If spark is present on one or more of the cylinders, inspect the spark plug wires for arching, cuts, rubbing on other components, and proper resistance, refer to Spark Plug Wire Inspection (Testing and Inspection).
• If all tests are normal, then the system is operating correctly.

Component Testing

* With positive polarity to the low reference terminal, measure for 9,000-11,000 ohms at 20-23°C (68-74°F) room temperature between each of the ignition coil control terminals and the low reference terminal of the IC module.

• If the resistance is not within the specified range, replace the IC module.

* Measure for 7,000-15,000 ohms at 20-23°C (68-74°F) room temperature between each pair of coil towers on the IC module.

• If the resistance is not within the specified range, replace the IC module.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Spark Plug Wire Replacement (Service and Repair)
* Spark Plug Replacement (Service and Repair)
* Ignition Coil Replacement (Service and Repair)