For 1990-2009 cars

### Diagnostic Instructions

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

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### Circuit/System Description

The ignition system uses individual ignition coil/module assemblies for each cylinder. The engine control module (ECM) controls the individual coils by transmitting timing pulses on the ignition control (IC) circuit of each ignition coil/module to enable a spark event. Each ignition coil/module has the following circuits:

• | An ignition voltage circuit

• | The ground circuit

• | An IC circuit

• | Low reference circuit

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Engine Control Module Scan Tool Information

#### Special Tools

J 26792 HEI Spark Tester

### Circuit/System Verification

Observe the Engine Controls Schematic for the ignition coils/modules, and review the Ignition System Specifications to verify the following:

• | The ignition coil/modules are correctly connected

• | The proper firing order

• | The proper spark plug type

• | The proper spark plug gap and torque

• | Refer to Ignition System Specifications.

### Circuit/System Testing

Note: Verify that the engine is in good mechanical condition before continuing with this diagnosis.

1. Turn the ignition OFF.
2. Inspect the fuse that supplies voltage to the ignition coil/modules.

⇒ | If the fuse is open, test the spliced circuits and the individual ignition coil/modules for a short to ground.

3. Disconnect the affected ignition coil/module.
4. Connect a test lamp between the ignition coil/module ignition 1 voltage circuit and a good ground.
5. With the test lamp still connected, measure for battery voltage between the ignition 1 voltage circuit and a good ground.

⇒ | If the voltage is within 0.5 V of battery voltage, repair the high resistance or the open in the ignition 1 voltage circuit.

6. Turn OFF the ignition and all electrical accessories. Allow sufficient time for all of the control modules to power down before taking a resistance measurement.
7. Measure for less than 5 ohms of a proper value between the ground circuit of the affected ignition coil/module and a good ground.

⇒ | If the resistance is more than 5 ohms, repair the high resistance or the open in the ground circuit.

8. Change the affected ignition coil/module with the ignition/coil module of a good cylinder.
9. Start the engine, and observe the scan tool.

⇒ | If the misfire occurs with the suspect ignition coil/module, replace as needed.

⇒ | If the misfire does not occur with the suspected ignition coil/module, observe the component testing procedures below, replace the spark plugs as needed.

### Component Testing

• | Use the Spark Plug Inspection procedure to verify the integrity of the spark plugs. Refer to Spark Plug Inspection.

• | Verify the output of each ignition coil/module using the J 26792 .

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Ignition Coil Replacement - Bank 1

• | Ignition Coil Replacement - Bank 2

• | Spark Plug Replacement