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 | 2 | 1 | B2585 00 | --
Park Lamp Switch On Signal | B257A 00 | B257A 00 | B257A 00 | --
Left Park Lamp Control | 3 | 3 | 3 | --
Right Park Lamp Control | 4 | 4 | 4 | --
Left Park Lamp Ground | -- | 3 | 3 | --
Right Park Lamp Ground | -- | 4 | 4 | --
Headlamp Switch Ground | -- | 5 | -- | --
1. All Park Lamps Inoperative 2. All Park Lamps Always On 3. Left Park Lamps Malfunction 4. Right Park Lamps Malfunction 5. Headlamps and Park Lamps Inoperative

### Circuit/System Description

The park, tail, marker, and license lamps are turned ON when the headlamp switch is placed in the PARK or ON position or anytime the headlights are requested. The underhood fuse block supplies B+ to both the park lamp relay switch contacts and the park lamp coil circuit. The body control module (BCM) provides a ground or control circuit to the park lamp circuit. When the park lamps are requested ON, the BCM energizes the park lamp relay. Current flow is from the park lamp relay to the individual park lamp circuit fuses and to their respective park, tail, marker, and license 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, command the park lamps ON and OFF with a scan tool. The park lamps should turn ON and OFF as commanded.

⇒ | If all park lamps are inoperative, refer to Park Lamps Inoperative - All

⇒ | If one or more, but not all, park lamps are inoperative, refer to Park Lamps Inoperative - One or More

⇒ | If the park lamps are always illuminated, refer to Park Lamps Always ON

2. Command the park lamps ON and OFF using the headlamp switch. Verify the scan tool Park Lamp Switch parameter cycles between Active and Inactive as commanded.

⇒ | If the parameter does not cycle between the specified values, refer to Park Lamp Switch Malfunction.

### Circuit/System Testing

#### Park Lamps Inoperative - All

1. Ignition OFF, disconnect the PRK LAMP relay.
2. Verify that 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.

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

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

4. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
5. Command the park 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.

6. Connect a 10A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87.
7. Disconnect the harness connector at the left tail lamp.
8. Test for less than 5.0 ohms between the appropriate ground circuit listed below and ground:

• | RPO W49/WDA - terminal B

• | RPO Z88 - terminal D

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

9. Verify that a test lamp illuminates between the appropriate control circuit terminal listed below and ground:

• | RPO W49/WDA - terminal C

• | RPO Z88 - terminal A

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

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

#### Park Lamps Inoperative - One or More

1. Ignition OFF, disconnect the harness connector at the appropriate park lamp.
2. Test for less than 5.0 ohms between the appropriate ground circuit terminal listed below and ground:

• | LF/RF Marker Lamp (WDA) - Terminal 1

• | LF/RF Marker Lamp (W49/Z88) - Terminal B

• | LR/RR Marker Lamp (WDA/W49) - Terminal B

• | Left/Right Tail Lamp Assembly (Z88) - Terminal D

• | Left/Right Tail Lamp (W49/WDA) - Terminal B

• | LR/RR Park Lamp (Z88) - Terminal 2

• | LR/RR Park Lamp (W49) - Terminal A

• | Left/Right License Lamp - Terminal B

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

3. Park lamps ON, verify a test lamp illuminates between the appropriate control circuit terminal listed below and ground:

• | LF/RF Marker Lamp (WDA) - Terminal 2

• | LF/RF Marker Lamp (W49/Z88) - Terminal A

• | LR/RR Marker Lamp (WDA/W49) - Terminal A

• | Left/Right Tail Lamp Assembly (Z88) - Terminal A

• | Left/Right Tail Lamp (W49/WDA) - Terminal A

• | LR/RR Park Lamp (Z88) - Terminal 1

• | LR/RR Park Lamp (W49) - Terminal B

• | Left/Right License Lamp - Terminal A

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

4. If all circuits test normal, test or replace the appropriate bulb or lamp assembly.

#### Park Lamps Always ON

1. Ignition OFF, disconnect the PRK LAMP relay.
2. Ignition ON, verify that the park lamps are not illuminated.

⇒ | If the park lamps are illuminated, test the control circuit for a short to voltage.

3. Ignition ON, connect a test lamp between the control circuit terminal 86 and B+. The test lamp should not illuminate.

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

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

#### Park Lamps Inoperative From Park Lamp Switch

1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Verify the scan tool Park Lamp Switch parameter is Inactive.

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

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

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

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Relay Replacement

• | Headlamp Switch Replacement

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