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 provide an overview of each diagnostic category.

### 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. The ignition coil consist of the following circuits:

• | The ignition 1 voltage

• | The IC 1 and 4 control

• | The IC 2 and 3 control

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Controls Component Views

• | Engine Control Module Connector End Views

#### Description and Operation:

Electronic Ignition (EI) System Description

#### 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

• | Scan Tool Output Controls

### 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.

Important: The test lamp is used to load the circuit and may not illuminate.

2. Connect a test lamp between the ignition 1 voltage circuit of the ignition coil and ground.
3. 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.

4. Ignition OFF, connect a DMM between the ignition 1 voltage circuit of the ignition coil from the fuse to the harness connector terminal of the ignition coil.

⇒ | If more than 2 ohms, repair the high resistance on the ignition 1 voltage circuit.

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.