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
--- | --- | --- | --- | ---
Park Lamp Relay B+ | 1 | 1 | -- | --
Park Lamp Switch Signal | 2 | 2 | 2 | --
Park Lamp Relay Control | 1 | 1 | B2585 00 | --
Park Lamp Control | 1 | 1 | 1 | --
Park Lamp Ground | -- | 1 | -- | --
Park Lamp Switch Low Reference | -- | 2 | -- | --
1. Park Lamps Malfunction 2. Park Lamp Switch Malfunction

### Circuit/System Description

Battery positive voltage is applied at all times to both the coil and switch sides of the PRK/LAMP relay located in the underhood fuse block. The turn signal/multifunction switch is supplied with ground at G106 at all times. When the headlamp and panel dimmer switch is placed in either the HEAD or PARK position, ground is applied to the park lamp signal circuit to the body control module (BCM). The BCM responds by applying ground to the park lamp relay control circuit. This energizes the park lamp relay coil causing the relay switch contacts to close allowing battery voltage to flow through the FRT PRK LAMP and REAR PRK LAMP fuses to all of the park, tail, license, and marker lamps.

### Reference Information

#### Schematic Reference

Exterior Lights Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Exterior Lighting Systems Description and Operation

#### 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

### Circuit/System Verification

1. Ignition ON, observe the scan tool park lamp switch parameter while cycling the park lamp switch ON and OFF. The readings should toggle between ACTIVE and INACTIVE.

⇒ | If the readings do not change between the commanded states, refer to Park Lamp Switch Malfunction.

2. Ignition ON, command the park lamps ON and OFF with a scan tool. The park lamps should turn ON and OFF.

⇒ | If the park lamps do not turn ON and OFF, refer to the Park or License Lamp Malfunction.

### Circuit/System Testing

#### Park Lamp Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the headlamp and panel dimmer switch.
2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal 3 and ground.

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

3. Ignition ON, verify the scan tool Park Lamp Switch parameter is OFF.

⇒ | If not the specified value, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the BCM.

4. Install a 3A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool Park Lamp Switch parameter is ON.

⇒ | If not the specified value, test the signal circuit for a short to voltage or open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the headlamp and panel dimmer switch.

#### Park or License Lamps Malfunction

1. Ignition OFF, disconnect the PRK LAMP relay.
2. Ignition ON, verify a test lamp does not illuminate between the control circuit terminal 87 and ground.

⇒ | If the test lamp illuminates, test the control circuit for a short to voltage.

3. Verify a test lamp illuminates between the B+ circuit terminal 30 and ground.

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

4. Verify a test lamp illuminates between the B+ circuit terminal 85 and ground.

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

5. Disconnect the harness connector at the inoperative park or license lamp.
6. Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms between the ground circuit and ground.

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

7. Connect the harness connector at the inoperative park or license lamp.
8. Connect a 15A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the park and license lamps are activated.

⇒ | If the park and license lamps do not activate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the inoperative park or license lamp.

9. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
10. Command the parking lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.

⇒ | If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

11. If all circuits test normal, test or replace the PRK LAMP relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Headlamp Switch Replacement

• | Park/Turn Signal/Side Marker Lamp Bulb Replacement

• | License Lamp Bulb Replacement

• | Tail Lamp Bulb Replacement