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 Control | B2585 06 | B2585 06 | B2585 01 | --
Park Lamp Switch ON Signal | 2 | 2 | 2 | --
License Lamp Supply Voltage | 1 | 1 | 1 | --
Marker Lamp Voltage Supply | 1 | 1 | 1 | --
Park Lamp Voltage Supply | 1 | 1 | 1 | --
License Lamp Ground | -- | 1 | 1 | --
Marker Lamp Ground | 1 | 1 | 1 | --
Park/Turn Lamp - LF Ground | -- | 1 | 1 | --
Park/Turn Lamp - RF Ground | -- | 1 | 1 | --
Tail/Stop and Turn Signal Lamps - LR Ground | -- | 1 | 1 | --
Tail/Stop and Turn Signal Lamps - RR Ground | -- | 1 | 1 | --
Turn Signal/Multifunction Switch Ground | -- | 2 | 2 | --
1. Park, License, Marker, and/or Tail Lamps Malfunction 2. Park Lamp Switch Malfunction

### Circuit/System Description

Battery voltage is applied at all times to the coil and switch sides of the PRK LAMPS relay located in the underhood fuse block. Ground is applied at G300 to the turn signal/multifunction switch at all times. When the headlamp switch is placed in either the HEAD or PARK position, ground is applied to the park lamp switch on signal circuit to the body control module (BCM). The BCM reacts to the signal from the park lamp switch by applying ground to the park lamp relay control circuit. This energizes the park lamp relay allowing voltage flows through the PRK LAMPS fuse through the switch contacts of the relay to all park, tail, license, and side marker lamps. Ground for the front park and side marker lamps is supplied at G101 for the left and G102 for the right. Ground for the license and right rear tail lamps is supplied at G402, and the left rear tail lamps at G400.

### Reference Information

#### Schematic Reference

Exterior Lights Schematics

#### Connector End View Reference

Lighting Systems Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Output Controls

• | Scan Tool Data List

• | Scan Tool Data Definitions

### Circuit/System Verification

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

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

### Circuit/System Testing

#### Park Lamp Switch Malfunction

1. Ignition OFF, disconnect the C1 harness connector at the turn signal/multifunction switch.
2. Test for less than 1.0 ohm of resistance 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 ON, verify the scan tool park lamp switch parameter is INACTIVE.

⇒ | If not the specified value, test the signal circuit terminal 3 for a short to ground. If the circuit tests normal, replace the BCM.

4. Install a 3-A fused jumper wire between the signal circuit terminal 3 and ground. Verify the scan tool park lamp switch parameter is ACTIVE.

⇒ | If not the specified value, test the signal circuit terminal 3 for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the turn signal/multifunction switch.

#### Park, License, Marker, and/or Tail Lamps Malfunction

1. Ignition OFF, disconnect the park lamp relay.
2. Ignition ON, verify that a test lamp does not illuminate between the relay controlled switched output circuit and ground.

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

3. Verify that a test lamp illuminates between the relay switch B+ circuit and ground.

⇒ | If the test lamp does not illuminate, test the relay switch B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the relay controlled switched output circuit for a short to ground. If the circuit tests normal, test or replace the park lamp relay.

4. Verify that a test lamp illuminates between the relay coil B+ circuit and ground.

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

5. Disconnect the harness connector at the inoperative park lamp.
6. Test for less than 1.0 ohm of resistance between the inoperative park lamp 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 lamp.
8. Connect a 15-A fused jumper wire between the relay switch B+ circuit and the relay controlled switched output circuit. Verify the park lamps are activated.

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

9. Connect a test lamp between the relay coil B+ circuit and the relay coil control circuit.
10. Command the parks 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 park lamp relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Parking and Turn Signal Lamp Replacement

• | Tail Lamp Replacement

• | Front Side Marker Lamp Replacement

• | License Lamp Bulb Replacement

• | Underhood Electrical Center or Junction Block Replacement

• | Relay Replacement

• | Turn Signal Multifunction Switch Replacement

• | Front Side Marker Lamp Bulb Replacement

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