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:

• | Ignition 1 voltage

• | Ground

• | IC

• | Low reference

### Diagnostic Aids

• | Depending on the location in the spliced ignition voltage circuit, a slight to moderate resistance can cause a misfire or a crank/no start concern.

• | Extended engine cranking time, will foul the spark plugs with excessive fuel and cause a crank/no start condition.

### 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 Tester

### Circuit/System Verification

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

• | Review the ignition system specifications and the spark plug inspection procedure 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 and Spark Plug Inspection.

• | If the engine will start, then observe the scan tool Misfire Current Cylinder parameters. This will indicate the affected ignition coil/modules.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the affected T8 ignition coil/modules.
2. Ignition OFF for 90 seconds, test for less than 5Ω between the ground circuit terminal 1 and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition OFF, test for less than 5Ω between the low reference circuit terminal 2 and ground.

⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.

4. Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit terminal 4 and ground.

⇒ | If the test lamp does not illuminate, test the ignition 1 voltage circuit for a short to ground or an open/high resistance.

5. Exchange the affected T8 ignition coil/module with the T8 ignition coil/module of a good cylinder.
6. Start the engine, observe the scan tool Misfire Current Cylinder parameters.

⇒ | If the misfire transfers with the suspect T8 ignition coil/module, replace it.

⇒ | If the misfire does not transfer with the suspect T8 ignition coil/module, replace the spark plug.

### Component Testing

Use the J 26792 to verify the output of each ignition coil/module.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Ignition Coil Replacement

• | Spark Plug Replacement