Battery 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 turn signal/multifunction switch is suppled 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 LAMP and RT PRK LAMP 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

Ignition ON, observe the scan tool Parklamp Switch parameter while cycling the park lamp switch ON and OFF. The readings should toggle between Active and Inactive.

Park Lamp Switch Malfunction

1. Ignition OFF, disconnect the X1 harness connector at the turn signal/multifunction switch.
2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal 1.

⇒	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 3 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 3 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 an open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the turn signal/multifunction switch.

Park, License, and/or Tail Lamps Malfunction

1. Ignition OFF, remove the fuse of the inoperative park/marker lamps and inspect.

⇒	If the fuse is OPEN, test the control circuit of the blown fuse for a short to ground.

2. Install the fuse.
3. Ignition OFF, disconnect the X2 harness connector at the underhood fuse block.
4. Connect a test lamp between the control circuit terminal 6 and B+.
5. 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 open/high resistance. If the circuit tests normal, replace the BCM.

6. Ignition OFF, connect the X2 harness connector at the underhood fuse block.
7. Disconnect the harness connector at the inoperative park/license/marker lamp.
8. Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms between the ground circuit terminal and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

9. Connect a test lamp between the inoperative park/license/marker lamp control circuit terminal and ground.
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 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.

11. If all circuits test normal, replace the inoperative park/license/marker lamp.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.