Electronic Ignition (EI) System Diagnosis

Electronic Ignition (EI) System Diagnosis

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* 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 module (ICM). The ICM contains coil driver circuits that command the coils to operate. The ICM 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 ICM for the proper coil to enable a spark event.

Diagnostic Aids

Inspect the spark plug wires for proper orientation.

Special Tools

* J 26792 Spark Tester
* J 43244 Relay Puller Pliers

Circuit/System Testing

1. With the ignition OFF, remove the fuel pump relay using the J 43244.
2. Crank the engine and test for a 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 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.
^ If there is no spark on any of the cylinders, test the ignition voltage circuit of the ICM for an open/high resistance or short to ground, or test the ground circuit of the ICM for an open/high resistance, or a faulty ICM. The wire circuit resistance should measure less than 3 ohms.
^ If spark is present on one or more of the cylinders, inspect and test the spark plug wires for arching, cuts, rubbing on other components, and proper resistance.
^ 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 ICM.

^ If the resistance is not within the specified range, replace the ICM.

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

^ If the resistance is not within the specified range, replace the ICM.

Repair Instructions

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

* Ignition Coil Replacement
* Spark Plug Replacement
* Spark Plug Wire Replacement