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

Ignition voltage is supplied to the ignition coil assembly. The engine control module (ECM) provides a ground for the ignition control (IC) circuits. When the ECM removes the ground path of the ignition primary coil, the magnetic field produced by the coil collapses. The collapsing magnetic field produces a voltage in the secondary coil which ignites the spark plugs. The sequencing and timing are controlled by the ECM.

Reference Information
Schematic Reference

Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Electronic Ignition System Description (Electronic Ignition System Description)
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 (Programming and Relearning) for scan tool information

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 for 1 minute, disconnect the harness connector at the ignition coil.
2. Test for less than 5 ohm between the ground circuit terminal B and ground.

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

3. Test for less than 5 ohm between the low reference circuit terminal C and ground.

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

4. Test for less than 2 ohm between the ignition voltage circuit terminal A and the fuse.

• If greater than the specified range, repair the ignition voltage circuit for high resistance.

5. Ignition ON, verify that a test lamp illuminates between the ignition voltage circuit terminal A and ground.

• If the test lamp does not illuminate, test the ignition voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition voltage circuit fuse is open, test all components connected to the ignition voltage circuit and replace as necessary.

6. If all circuits test normal, test or replace the ignition coil assembly.

Repair Instructions

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

* Ignition Coil Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming