Circuit/System Testing

Ignition ON/vehicle in service mode, exterior lamps OFF.
Connect a test lamp between the trailer backup lamp Fuse F33UA and ground.

NOTE:

Scan tool control functions can be found under the K219 Lighting Control Module.

Verify the test lamp turns ON and OFF when commanding the Trailer Backup Lamps ON and OFF with a scan tool.
- If the test lamp is always OFF
1. Test the ground circuit at the X50A Engine Wiring Harness Junction Block for an open/high resistance.
  - If an open/high resistance is found, repair the fault on the ground circuit or ground connection.
  - Go to next step: If an open/high resistance is not found.
2. Test control circuit 38 for a short to ground.
  - If a short to ground is found, repair the fault on the circuit.
  - Go to next step: If a short to ground is not found.
3. Test control circuit 38 for an open/high resistance.
  - If an open/high resistance is found, repair the fault on the circuit.
  - Go to next step: If an open/high resistance is not found.
4. Replace the X50A Engine Wiring Harness Junction Block.
- If the test lamp is always ON
1. Test control circuit 38 for a short to voltage.
  - If a short to voltage is found, repair the fault on the circuit.
  - Go to next step: If a short to voltage is not found.
2. Replace the X50A Engine Wiring Harness Junction Block.
- Go to next step: If the test lamp turns ON and OFF
Replace the K219 Lighting Control Module.