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.

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

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 Parking Lamps Switch Malfunction.

2. Ignition ON, command the Parking Lamps ON and OFF with a scan tool. The Parking Lamps should turn ON and OFF.

⇒	If the parking lamps do not turn ON and OFF between the commanded states, refer to Park Lamp Malfunction.

Park Lamp Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Ignition OFF, test for less than 5.0 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 3A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool BCM 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. Connect a test lamp between the control circuit terminal 87 and ground. The test lamp should not illuminate.

⇒	If the test lamp illuminates, test the control circuit for a short to voltage.

3. Connect a test lamp between the relay B+ terminals 30 and ground. The test lamp should illuminate.

⇒	If the test lamp does not illuminate, test the B+ circuit for short to ground.

4. Connect a test lamp between the relay B+ terminal 86 and ground. The test lamp should illuminate.

⇒	If the test lamp does not illuminate, test the B+ circuit for short to ground.

5. Connect a 15A fused jumper wire between the relay B+ circuit terminal 30 and the park lamp control circuit terminal 87. The Park/Tail lamps should illuminate.

⇒	If the Park/Tail lamps do not illuminate, and the appropriate PARK lamp fuse tests normal, test the park lamp control circuit for a short to ground or an open/high resistance.

6. Connect a test lamp between the relay control circuit terminal 85 and B+ circuit terminal 86.
7. Ignition ON, command the Parking Lamps ON and OFF with a scan tool. The test should turn ON and OFF.

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

⇒	If the test lamp is always ON, test the relay control circuit for a short to ground. If the circuit tests normal, replace the BCM.

8. Ignition OFF, disconnect the harness connector at the appropriate park, marker, license, or tail lamp.
9. Verify that a test lamp illuminates when connected between battery voltage and the listed ground circuit terminal below.

•	Park/Turn Signal Lamp -- Left of Right front terminal C -- with X88

•	Park/Turn Signal Lamp -- Left of Right front terminal G -- with Z88

•	Marker Lamp -- Left or Right front terminal A -- with Z75

•	Marker Lamp -- Left or Right front terminal B -- with Z88 or X88

•	Park Lamp -- Left or Right front terminal B -- Z75

•	Tail/Stop and Turn Signal Lamp -- Lower Left or Right rear terminal G -- w/o X88 - E52

•	Tail/Stop and Turn Signal Lamp -- Upper Left or Right rear terminal GND -- with X88 - E52

•	Tail/Turn Signal Lamp -- Left or Right terminal G -- w/o X88 + E52

•	Tail/Turn Signal Lamp -- Left or Right terminal GND -- with X88 + E52

•	Tail/Stop Lamp -- Left or Right Rear terminal G -- w/o X88 + E52

•	Tail/Stop Lamp -- Left or Right Rear terminal GND -- w/o X88 + E52

•	Marker Lamp -- Left or Right Rear terminal B -- with Z88

•	Marker Lamp -- Left or Right Rear terminal A -- with Z75 or X88 - E52

•	Tail Lamp Circuit Board -- Left or Right Rear terminal D -- with Z75 + E52

•	License lamp terminal B

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

10. Ignition ON, connect a test lamp between the listed control circuit terminal and ground.

•	Park/Turn Signal Lamp -- Left of Right front terminal B -- with X88

•	Park/Turn Signal Lamp -- Left of Right front terminalB -- with Z88

•	Marker Lamp -- Left or Right front terminal D -- with Z75

•	Marker Lamp -- Left or Right front terminal A -- with Z88 or X88

•	Park Lamp -- Left or Right front terminal A -- Z75

•	Tail/Stop and Turn Signal Lamp -- Lower Left or Right rear terminal B -- w/o X88 - E52

•	Tail/Stop and Turn Signal Lamp -- Lower Left or Right rear terminal MNR -- with X88 - E52

•	Tail/Turn Signal Lamp -- Left or Right Rear terminal B -- w/o X88 + E52

•	Tail/Turn Signal Lamp -- Left or Right Rear terminal MNR -- with X88 + E52

•	Tail/Stop Lamp -- Left or Right Rear terminal B -- w/o X88 + E52

•	Tail/Stop Lamp -- Left or Right Rear terminal MNR -- with X88 + E52

•	Marker Lamp -- Left or Right Rear terminal B -- with Z88

•	Marker Lamp -- Left or Right Rear terminal A -- with Z75 or X88 - E52

•	Tail Lamp Circuit Board -- Left or Right Rear terminal A -- with Z75 + E52

•	License lamp terminal A

11. Ignition ON, 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 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, and the appropriate park lamp fuse tests normal, replace the underhood fuse block.

12. If all circuits test normal, test or replace the appropriate lamp.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.