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

This ignition system uses individual ignition module/coil assemblies for each cylinder. The engine control module (ECM) controls the spark events by transmitting the timing pulses on the ignition control (IC) circuits to the individual ignition module/coil assemblies in firing order sequence. Each ignition module/coil has the following circuits:

• | An ignition 1 voltage circuit

• | A ground circuit

• | An IC circuit

• | A low reference circuit

### Diagnostic Aids

• | This test procedure requires that the vehicle battery has passed a load test and is completely charged.

• | There is an adequate supply of fuel in the fuel tank.

• | When disconnecting electrical connectors or removing fuses and relays from a fuse block, always inspect both mating electrical terminals for corrosion and terminal tightness.

• | Use the J 35616 for any test that requires probing the underhood fuse block terminals, component wire harness terminals, or the ECM wire harness terminals.

### 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

Control Module References for scan tool information

#### Special Tools

• | J 26792 Spark Plug Tester

• | J 35616-A/BT-8637 Connector Test Adapter Kit

### Circuit/System Verification

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

• | The ignition modules/coils are correctly wired and connected

• | The proper spark plug type

• | The proper spark plug gap and torque

• | The proper ohm values for the spark plug wires

| Refer to Ignition System Specifications.

### Circuit/System Testing

1. Turn OFF the ignition.

Important: This engine application uses 2 fuses, one for each bank, to supply ignition 1 voltage to the ignition module/coil assemblies and also to the fuel injectors. A good indication that a fuse is open is that all 4 misfire counters are incrementing on one side of the engine

2. Inspect both fuses that supply ignition voltage to the ignition module/coils.

⇒ | If a fuse is open, test all 8 ignition voltage circuits to the ignition module/coils or the fuel injectors on that engine bank, for a short to ground.

3. Disconnect the 4 ignition module/coil, and the 4 fuel injector electrical connectors, for the engine bank that has the open fuse.
4. Replace the open fuse with a new fuse.
5. Ignition ON, engine OFF.
6. Reconnect each ignition module/coil, and fuel injector electrical connectors, one at a time.

⇒ | If the fuse opens when connecting an ignition module/coil or fuel injector electrical connector, then replace the component that caused the fuse to open.

7. Ignition OFF, disconnect the appropriate ignition module/coil electrical connector.
8. Ignition ON, verify that a test lamp illuminates between the ignition voltage circuit and ground.

⇒ | If the test lamp does not illuminate test the ignition voltage circuit for an open/high resistance.

9. Verify that a test lamp illuminates between the ignition module/coil ground circuit and B+.

⇒ | If the test lamp does not illuminate, test the ignition module/coil ground circuit for an open/high resistance.

10. Inspect and measure the resistance of the spark plug wire. Refer to Spark Plug Wire Inspection and Ignition System Specifications.

⇒ | If the resistance value is not within the specified range, or does not pass the inspection, replace the spark plug wire.

11. Exchange the misfiring cylinder, ignition module/coil assembly with the ignition module/coil assembly from a non-misfiring cylinder.
12. Start and idle the engine. Observe the misfire counters on the scan tool.

⇒ | If the misfire transfers with the suspect ignition module/coil, then replace the ignition module/coil assembly.

⇒ | If the misfire does not transfer with the suspect ignition module/coil, then measure the resistance of the IC circuit. The IC circuit should measure less than 5 ohms. If the circuit tests normal, replace the ECM.

### Component Testing

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

| Important: An erratic or weak spark is considered a no spark condition.

• | Use the J 26792 to verify the output of each ignition module/coil. If no spark is detected across the gap of the spark plug tester, then replace the ignition module/coil assembly.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Engine Control Module Programming and Setup

• | Engine Control Module Replacement

• | Ignition Coil Replacement

• | Spark Plug Replacement