Park, License, and/or Tail Lamps Malfunction
Park, License, and/or Tail Lamps Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
B+ is applied at all times to both the coil and switch sides of the PARK LAMP Relay located in the underhood fuse block. The turn signal/multifunction switch is supplied with ground 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 B+ to flow through the LT PRK, RT PRK, and TRLR 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 1-2 Shift Solenoid (SS) Valve (M30)
Description and Operation
Exterior Lighting Systems Description and Operation Exterior Lighting Systems
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON, observe the scan tool Parklamp Switch parameter while cycling the headlamp switch between the OFF and Park positions. The parameter should toggle between Active and Inactive.
• If the readings do not change between the commanded states, refer to Park Lamp Switch Malfunction.
2. Command the Parking Lamps ON and OFF with a scan tool. The park lamps should turn ON and OFF when changing between the commanded states.
• If the park lamps do not turn ON and OFF when commanded, refer to 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. Test for less than 1.0 ohms between the ground circuit terminal 8 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Parklamp 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 3 A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool Parklamp 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.
Park Lamps Malfunction
1. Ignition OFF, disconnect the park 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 85 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 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.
5. Disconnect the harness connector at the appropriate park lamp.
6. Test for less than 5 ohms between the park lamp ground circuit terminal listed below and ground:
* Park/Turn Signal Lamp - Terminal G
* Tail/Stop and Turn Signal Lamp - Terminal GRD
* License Lamp - Terminal B
* Rear Fender Clearance Lamp - Terminal B
* Side Marker Lamp - Terminal A
* Roof Clearance Lamp - Terminal A
* Tailgate Marker Lamp - Terminal B
• If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
7. Connect the harness connector at the park lamp.
8. Connect a 15 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the park lamp is activated.
• If the park lamp does not activate and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, replace the park lamp.
• If the park lamp does not activate and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, replace the park 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 park lamp relay.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Parking and Turn Signal Lamp Bulb Replacement (Chevrolet) Service and RepairParking and Turn Signal Lamp Bulb Replacement (GMC) Service and Repair
* Rear License Plate Lamp Replacement (Silverado GMC) Rear License Plate Lamp Replacement (Silverado GMC)Rear License Plate Lamp Replacement (VF7) Rear License Plate Lamp Replacement (VF7)
* Tail Lamp Bulb Replacement (Chevrolet) Service and RepairTail Lamp Bulb Replacement (GMC) Service and Repair
* Headlamp Switch Replacement (without RPO SLT) Headlamp Switch Replacement (without RPO SLT)Headlamp Switch Replacement (with RPO SLT) Headlamp Switch Replacement (with RPO SLT)
* Control Module References Control Module References for BCM replacement, programming, and setup.