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.

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 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 Parklamp Switch Malfunction.

2. Ignition ON, 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 Malfunction.

Parklamp Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Test for less than 5 ohms 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 Malfunction

1. Ignition OFF, disconnect the appropriate park or license lamp.
2. Test for less than 5 ohms between the listed ground circuit terminals and ground.

•	Park/Turn Signal Lamp terminal C

•	Tail/Stop and Turn lamp terminal G

•	Marker or License lamp terminal B

•	Roof Marker Lamps terminal B

⇒	If greater than the specified range, 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/Turn Signal Lamp terminal B

•	Tail/Stop and Turn lamp terminal B

•	Marker or License lamp terminal A

•	Roof Marker Lamps terminal A

4. Turn the park lamp switch On and Off and verify that the test lamp turns ON and OFF.

⇒	If the test lamp does not illuminate, test the control circuit for a short to ground or 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.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.