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 vehicle park, license, and tail lamps are controlled by the body control module (BCM) based on an input from the headlamp switch. The headlamp switch has four positions: Off, Auto, Park, and Headlamps. The default headlamp switch position is Auto, in which the BCM uses the ambient light sensor to determine when exterior lamps are needed. The Off portion of the headlamp switch is a momentary switch which overrides the automatic lamps and will turn off the vehicle lamps. The Park position of the headlamp switch will only illuminate the vehicle parking lamps. The Headlamp position of the headlamp switch will illuminate both the parking lamps, as well as the headlamps. With the headlamp switch in the Park position, the park lamp switch on signal circuit is grounded prompting the BCM to turn ON the exterior lamps, regardless of other factors such as ambient light.
When a park lamp request is received, the BCM grounds the park lamp relay control circuit. This energizes the PARK LP PCB relay. Battery voltage is then applied through the switch side of the relay, the LT PARK and RT PARK fuses illuminating the front park, license, tail, and marker lamps.
Reference Information
Schematic Reference
Exterior Lights Schematics Exterior Lights Schematics
Connector End View Reference
Component Connector End Views A/C Compressor Clutch
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 BCM Parklamp Switch parameter while cycling the headlamp switch between the Park and Auto positions. The parameter should change between Active and Inactive.
• If the parameter does not change between the specified values, refer to Headlamp Switch Malfunction.
2. Command the Parking Lamps ON and OFF with a scan tool. The front park, license, and tail lamps should turn ON and OFF when changing between the commanded states.
• If all of the lamps are always OFF or remain ON, refer to the Park Lamp Relay Malfunction.
• If one or more of the lamps is always OFF, refer to Park Lamps Malfunction.
Circuit/System Testing
Headlamp Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Ignition OFF, verify that a test lamp illuminates between the ground circuit terminal 8 and B+.
• If the test lamp does not illuminate, 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 and open/high resistance. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, test or replace the headlamp switch.
Park Lamp Relay Malfunction
1. Ignition OFF, disconnect the harness connector X2 at the underhood fuse block.
2. Connect a test lamp between the control circuit terminal K2 and B+.
3. Ignition ON, 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.
4. If the circuit tests normal, replace the underhood fuse block.
Park Lamps Malfunction
1. Ignition OFF, disconnect the harness connector at the appropriate exterior lamp.
2. Ignition OFF, test for less than 5.0 ohms between the ground circuit terminal listed below and ground.
* Marker Lamps terminal B
* Tail Lamps terminal B
* License Lamp terminal B
* Tail/Stop/Turn Signal Lamps terminal G
* Front Park/Turn Signal Lamps terminal G
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the control circuit terminal listed below and ground.
* Marker Lamps terminal A
* Tail Lamps terminal A
* License Lamp terminal A
* Tail/Stop/Turn Signal Lamps terminal B
* Front Park/Turn Signal Lamps terminal B
4. Ignition ON, 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 voltage. If the circuit tests normal, replace the underhood fuse block.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the underhood fuse block.
5. If all circuits test normal, test or replace the park lamp.
Component Testing
Headlamp Switch
Note:
If the switch tests open in any switch position other than Auto, test the switch signal circuits for a short to voltage before replacing the switch.
1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Test for infinite resistance between the signal terminal 1 and the ground terminal 8 with the switch in the Auto position.
• If not the specified value, replace the headlamp switch.
3. Test for less than 2.0 ohms between the signal terminal 1 and the ground terminal 8 with the switch in the Headlamp ON position.
• If greater than the specified value, replace the headlamp switch.
4. Test for infinite resistance between the signal terminal 2 and the ground terminal 8 with the switch in the Auto position.
• If not the specified value, replace the headlamp switch.
5. Test for less than 2.0 ohms between the signal terminal 2 and the ground terminal 8 with the switch in the Park position.
• If greater than the specified value, replace the headlamp switch.
6. Test for infinite resistance between the signal terminal 3 and the ground terminal 8 with the switch in the Auto position.
• If not the specified value, replace the headlamp switch.
7. Test for less than 2.0 ohms between the signal terminal 3 and the ground terminal 8 with the switch in the Off position.
• If greater than the specified value, replace the headlamp switch.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Headlamp Switch Replacement (Impala) Service and Repair
* Headlamp Bulb Replacement Service and Repair
* Tail Lamp Bulb Replacement (Impala) Service and Repair
* Rear Turn Signal Lamp Bulb Replacement Service and Repair
* Rear License Plate Lamp Replacement (Impala) Service and Repair
* Accessory Wiring Junction Block Replacement Accessory Wiring Junction Block Replacement
* Control Module References Control Module References for BCM replacement, setup and programming