Operation CHARM: Car repair manuals for everyone.
Home >> GMC Truck >> 2009 >> Yukon XL 4WD V8-5.3L >> Repair and Diagnosis >> Lighting and Horns >> Testing and Inspection >> Symptom Related Diagnostic Procedures >> Park, License, and/or Tail Lamps Malfunction (Front LED Park/Marker Lamps with T4Q)

Park, License, and/or Tail Lamps Malfunction (Front LED Park/Marker Lamps with T4Q)




Park, License, and/or Tail Lamps Malfunction (Front LED Park/Marker Lamps with T4Q)

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (with HP2) (Initial Inspection and Diagnostic Overview)Diagnostic System Check - Vehicle (without HP2) (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.

Diagnostic Fault Information





Circuit/System Description

Battery positive voltage is applied at all times to both the coil and switch sides of the PARK LAMP Relay located in the underhood fuse block. The Headlamp and Panel Dimmer switch is supplied with ground at G201 at all times. When the headlamp 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 LT PRK fuses and RT PRK fuses to all of the park, tail, license, and marker lamps.

Reference Information
Schematic Reference

Exterior Lights Schematics (Exterior Lights Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

1. Ignition ON, observe the scan tool Parking 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 Parking Lamps ON and OFF with a scan tool. The front LED park lamps should turn ON and OFF when changing between the commanded states.

• If the front LED park lamps do not turn ON and OFF when commanded, refer to Front LED Park Lamps 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, verify that a test lamp illuminates between B+ and the ground circuit terminal 8.

• If the test lamp does not illuminate, 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 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 Active.

• 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.

Front LED Park Lamps Malfunction
1. Ignition OFF, disconnect the PRK LAMP relay.
2. Ignition ON, verify that 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 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 a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal 87 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 B+ circuit terminal 86 and ground.

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

5. Disconnect the harness connector at the inoperative headlamp/park lamp assembly.
6. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal J 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 headlamp/park lamp assembly.
8. Connect a 20A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the marker lamps illuminate.

• If all of the front park/marker lamp LEDs do not illuminate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the headlamp control module.
• If some of the front park/marker lamp LEDs illuminate, replace the appropriate headlamp assembly.

9. Connect a test lamp between the control circuit terminal 85 and B+ circuit terminal 86.
10. 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.

11. If all circuits test normal, test or replace the park lamp relay.

Repair Instructions

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

* Headlamp Switch Replacement (Cadillac) (Service and Repair)Headlamp Switch Replacement (Except Cadillac) (Service and Repair)
* Headlamp Replacement (Non HID) (Service and Repair)Headlamp Replacement (Cadillac Escalade) (Service and Repair)Headlamp Replacement (Escalade PLATINUM) (Service and Repair)Headlamp Replacement (Tahoe, Avalanche) (Service and Repair)Headlamp Replacement (Chrevrolet Tahoe Two-mode Hybrid) (Service and Repair)Headlamp Replacement (Yukon) (Service and Repair)Headlamp Replacement (GMC Yukon Two-mode Hybrid) (Service and Repair)
* Control Module References (Programming and Relearning) for BCM or headlamp control module replacement, setup, and programming

pro multis · About Operation CHARM