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.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Parklamp Control Circuit | B2585 00 B3867 00 | B2585 00 B3867 00 | B2585 00 B3867 00 | --
Headlamp Switch Parklamp Signal Circuit | 1 | 2 | -- | --
Headlamp Switch Parklamp Ground Circuit | -- | 2 | 2 | --
Headlamp Switch | 1 | 2 | 2 | --
1. Parklamp Always ON 2. Parklamp Inoperative

### Circuit/System Description

The body control module (BCM) controls the park lamp relay by grounding the control circuit on the park lamp relay when the headlamp switch is turned to the PARK or the HEAD position. This energizes the park lamp relay, illuminating the park lamps.

### Diagnostic Aids

A short to ground, a short to voltage or an open in the following location may cause a malfunction to occur:

• | The park lamp relay control circuit

• | The park lamp relay

• | The headlamp switch supply circuit

• | The headlamp switch ground circuit

• | The headlamp switch

• | The BCM

### Reference Information

#### Schematic Reference

Exterior Lights Schematics

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Data Definitions

• | Scan Tool Data List

• | Scan Tool Output Controls

### Circuit/System Verification

Ignition ON, turn the headlamps ON with the headlamp switch. Observes the park lamps, the park lamps should be ON.

### Circuit/System Testing

#### Parklamp Switch Circuit Testing

1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Verify that the park lamps are OFF

⇒ | If not OFF, test the signal circuit for a short to ground. If the circuit tests normal, replace the BCM.

3. Install a 3-amp fused jumper wire between the signal circuit and ground. Verify that the park lamps are ON.

⇒ | If not ON, test the signal circuit of the headlamp switch for a short to voltage or an open/high resistance. If circuit tests normal, replace the BCM.

4. If all circuits test normal, test or replace the headlamp switch.

### Component Testing

#### Parklamp Switch Testing

1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Test for infinite resistance between the signal terminal and the voltage supply terminal with the switch in the open position.

⇒ | If less than infinite resistance, replace the headlamp switch.

3. Test for less than 1.5 ohms between the signal terminal and the voltage supply terminal with the switch in the closed position.

⇒ | If greater than 1.5 ohms, replace the headlamp switch.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Control Module References for BCM replacement, setup, and programming

• | Turn Signal Multifunction Switch Replacement