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
The park, tail, marker, license and clearance lamps are turned ON when the headlamp switch is placed in the PARK or ON position or anytime the headlights are requested On. The underhood fuse block supplies B+ to both the park lamp relay switch contacts and the park lamp relay coil circuit. The body control module (BCM) supplies a ground 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, license and clearance lamps. The front park, marker, tail, license and clearance lamps are grounded at G105, G350, G340 and G420. If the driver places the headlight switch in the ON position after the ignition switch has been turned OFF, the park, tail, marker, license and clearance lamps will remain ON until turned OFF.
Reference Information
Schematic Reference
Exterior Lights Schematics (Exterior Lights Schematics)
Connector End View Reference
Component Connector End Views (Component Connector End 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 BCM Parklamp Switch parameter while cycling the headlamp switch between the Park and Off positions. The parameter should cycle between Active and Inactive.
• If the parameter does not cycle between the specified values, refer to Headlamp Switch Circuit Test.
2. Command the Parking Lamps ON and OFF with a scan tool. Verify the park, license, and tail lamps turn ON and OFF.
• If any of the lamps do not cycle between the commanded states, refer to Exterior Lamps Circuit Test.
Circuit/System Testing
Headlamp Switch Circuit Test
1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Test for less than 1.0 ohm between the low reference circuit terminal 3 and ground.
• If greater than the specified range, test the low reference circuit for an open/high resistance.
3. Ignition ON, verify the scan tool BCM Parklamp Switch parameter is Off.
• 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 BCM Parklamp Switch parameter is On.
• 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 switch.
Exterior Lamps Circuit Test
1. Ignition OFF, disconnect the appropriate park or license lamp bulb.
2. Verify that a test lamp illuminates when connected between B+ and the listed ground circuit terminal.
* Park lamp terminal C
* Tail lamp terminal G
* Marker or license lamp terminal B
• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
3. Ignition ON, connect a test lamp between the listed control circuit terminal and ground.
* Park or tail lamp terminal B
* Marker or license lamp terminal A
4. Turn the park lamp switch On and Off and verify that the test lamp turns on an off.
• If the test lamp does not illuminate, test the control circuit for an open/high resistance.
• If the test lamp remains illuminated, test the control circuit for a short to voltage.
5. If all circuits test normal, replace the appropriate bulb.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Headlamp Switch Replacement (Service and Repair)
* Front Side Marker Lamp Bulb Replacement (Front Side Marker Lamp Bulb Replacement)
* Park/Turn Signal Lamp Bulb Replacement (Service and Repair)
* Rear License Lamp Replacement (with BRM and RHD) (Rear License Lamp Replacement (with BRM and RHD))Rear License Lamp Replacement (Base) (Rear License Lamp Replacement (Base))
* Tail Lamp Bulb Replacement (Service and Repair)