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

Each engine cylinder has a dedicated ignition coil assembly. The ignition coil assembly contains the ignition module circuitry. The power distribution circuit supplies system voltage to each coil assembly when the ignition switch is in the ON or START positions. Each coil assembly regulates current flow through the primary coil windings, creating a magnetic field. The powertrain control module (PCM) signals each coil assembly to supply a spark in a cylinder through the ignition control (IC) circuit. Each assembly does so by opening the primary circuit coil, inducing a high voltage in the secondary circuit coil. The high voltage in the secondary circuit grounds by arcing at the spark plug. This event creates a pulse on the fail safe circuit that the PCM recognizes as a confirmation of spark. The ignition coil consist of the following circuits:

* The ignition voltage circuit
* The ignition control (IC) circuit
* The ignition fail-safe circuit
* The ground circuit

Diagnostic Aids

Inspect for any of the following conditions:

* Any circuit malfunction between the ignition coil assembly and the PCM should set a fail safe circuit DTC P0351, P0352, P0353, or P0354.
* Check the crankshaft position (CKP) sensor engine reference signal with a scan tool. Observe the Engine Speed parameter while cranking the engine. The scan tool should indicate a steady 200-300 RPM while cranking. If erratic values, such as sudden spikes in the engine speed, are displayed, the engine reference signal is not stable enough for dependable ignition system operation.
* An ignition system that tests OK after sitting may be susceptible to moisture. Spray water on the ignition system components and wiring in order to check for an intermittent condition.

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 (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)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information
Special Tools

J 26792 Spark Tester

Circuit/System Testing

Note: 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 at the ignition coil.
2. Test for less than 5 ohm between the ground circuit terminal 4 and ground.

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

3. Ignition ON, verify that a test lamp illuminates between the ignition voltage circuit terminal 1 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.

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

Repair Instructions

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

* Spark Plug Replacement (Service and Repair)
* Ignition Coil Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for control module replacement, setup, and programming