Ignition System: Testing and Inspection

Electronic Ignition (EI) System Diagnosis

Diagnostic Fault Information

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

Circuit/System Description

Ignition 1 voltage is supplied to the ignition coil. The engine control module (ECM) provides a ground for the ignition coil (IC) control 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 Electrical Diagrams

Connector End View Reference
* Engine Control Module (ECM) Connector End Views Engine Control Module (ECM) Connector End Views
* Engine Controls Connector End Views Engine Controls Connector End Views

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
* Scan Tool Data List (w/o Throttle Actuator Control) Scan Tool Data List (w/o Throttle Actuator Control)Scan Tool Data List (w/Throttle Actuator Control) Scan Tool Data List (w/Throttle Actuator Control)
* Scan Tool Data Definitions Scan Tool Data Definitions
* Scan Tool Output Controls Scan Tool Output Controls

Special Tools Required
* J 26792 Spark Tester
* J 43244 Relay Puller Pliers

Circuit/System Testing

Important: Do not perform this diagnostic procedure if you were not sent here from a misfire DTC or the Engine Cranks but Does Not Run diagnostic.


1. Ignition OFF, disconnect the harness connector of the ignition coil.
2. Ignition ON, load test for battery voltage between the ignition 1 voltage circuit of the ignition coil and ground.

• If less than B+, repair the ignition 1 voltage circuit of the ignition coil for a short to ground or an open/high resistance.

3. Ignition OFF, test for less than 5 Ohms of resistance between the ground circuit of the ignition coil and the negative terminal of the battery.

• If greater than 5 Ohms, repair the ground circuit of the ignition coil for an open/high resistance.

4. If all circuits/connections test normal, replace the ignition coil.

Repair Instructions

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

Ignition Coil(s) Replacement Service and Repair