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Park, License, and/or Tail Lamps Malfunction



Park, License, and/or Tail Lamps Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* 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/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 battery positive voltage 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 relay coil 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.

Circuit/System Verification

1. Ignition ON, command the park lamps ON and OFF with a scan tool. The park lamps should illuminate when commanded ON.

^ If the park lamps do not illuminate, refer to Park Lamps Inoperative From BCM.

^ If the park lamps are always illuminated, refer to Park Lamps Always On From Relay.

2. Refer to Park Lamps Inoperative From Switch.

Circuit/System Testing

Park Lamps Inoperative From BCM
1. Ignition OFF, disconnect the PRK LAMP relay.
2. Ignition ON, verify that a test lamp does not illuminate between the relay controlled output circuit terminal 87 and ground.

^ If the test lamp illuminates, test the relay controlled output circuit for a short to voltage.

3. Verify that a test lamp illuminates between the relay coil B+ circuit terminal 85 and ground.

^ If the test lamp does not illuminate, test the relay coil B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the relay coil B+ circuit fuse is open, test the relay controlled output circuit for a short to ground. If the circuit tests normal, test or replace the PRK LAMP relay.

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

^ If the test lamp does not illuminate, test the relay switch B+ circuit for an open/high resistance.

5. Connect a test lamp between the relay coil B+ circuit terminal 85 and the relay coil control circuit terminal 86.
6. 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 relay coil control circuit for a short to ground. If the circuit tests normal, replace the BCM.

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

7. 8. Connect a 10A fused jumper wire between the relay switch B+ circuit terminal 30 and the relay controlled output circuit terminal 87.
8. Disconnect the harness connector at the left tail lamp.
9. Verify that a test lamp illuminates between the park lamp voltage supply circuit listed below and ground:

* RPO W49/WDA - terminal C
* RPO Z88 - terminal A

^ If the test lamp does not illuminate, test the voltage supply circuit for a short to ground or an open/high resistance.

10. Verify that a test lamp illuminates between the park lamp ground circuit listed below and B+:

* RPO W49/WDA - terminal B
* RPO Z88 - terminal D

^ If the test lamp does not illuminate, test the ground circuit for a open/high resistance.

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

Park Lamps Always On From Relay
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 relay controlled output circuit for a short to voltage.

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

^ If the test lamp illuminates, test the relay coil 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 Switch
1. Disconnect the harness connector at the headlamp switch.
2. Install a 3A fused jumper wire between the park lamp switch 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 terminal 2 for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

3. Test the signal circuit terminal 2 for a short to ground. If all circuits test normal, replace the headlamp switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Relay Replacement (Attached to Wire Harness) Relay Replacement (Within an Electrical Center)
* Headlamp Switch Replacement
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