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

Ignition 1 voltage is supplied to the ignition coils. 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.

### Diagnostic Aids

• | The ignition coils for each bank are fused separately. If a fuse opens or the ignition 1 voltage circuit opens between the fuse and the splice, all the ignition coils for one bank of the engine would be inoperative. If the ground circuit opens at the engine block, the ignition coils would be inoperative for one bank of the engine

• | Inspect the ignition coils for aftermarket devices. An aftermarket device connected to the ignition coil circuits, may cause a condition with the ignition coils.

### 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

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### 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 appropriate ignition coil.
2. Ignition ON, load test for B+ between the ignition voltage circuit terminal listed below and ground.

• | Terminal D for LY7

• | Terminal 2 for LLT

⇒ | If less than B+, repair the ignition voltage circuit of the ignition coil for a short to ground or an open/high resistance.

3. Crank or start the engine. Test for 200-400 mV between the IC circuit terminal listed below and ground.

• | Terminal C for LY7

• | Terminal 1 for LLT

⇒ | If less than the specified range, test the IC circuit for a short to ground or an open/high resistance. If the circuit/connection tests normal, replace the ECM.

⇒ | If greater than the specified range, test the IC circuit for a short to voltage. If the circuit/connection tests normal, replace the ECM.

4. Connect a test lamp between the each of the ground circuits terminal listed below, and B+. The test lamp should illuminate on each circuit.

• | Terminal A for LY7

• | Terminal 3 for LLT

• | Terminal 4 for LLT

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

Note: This step only applies to the LY7 engine.

5. Ignition OFF, test for less than 5 Ω between the low reference circuit terminal B 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 ECM.

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

### Repair Instructions

Perform the Diagnostic Repair Verification.

• | Ignition Coil Replacement - Bank 1

• | Ignition Coil Replacement - Bank 2