Inspection And Verification
CAUTION:
Diagnosis by substitution from a donor vehicle is NOT
acceptable. Substitution of control modules does not guarantee confirmation of a fault and may also cause additional faults in the vehicle being checked and/or the donor vehicle.
NOTE:
Check and rectify basic faults before beginning diagnostic routines involving pinpoint tests.
NOTE:
Prior to carrying out fault diagnosis of the trailer lamp system, verify the operation of the towing vehicle lighting system with the trailer lighting plug(s) disconnected from the vehicle socket(s).
- Verify the customer concern.
- Visually inspect for obvious signs of mechanical or electrical damage.VISUAL INSPECTION
Mechanical Electrical - Trailer lamp(s) condition and installation
- Bulbs and installation
- Bulb holders and installation
- Trailer socket(s), plug(s) and installation
- Fuses
- Relays
- Stop lamp switch
- Wiring harness
- Loose or corroded connector(s)
- Trailer socket(s) ground circuit(s)
- Battery Junction Box (BJB)
- Central Junction Box (CJB)
- Trailer fuse box
- Trailer relay box
- Instrument Cluster (IC)
- Controller Area Network (CAN) circuits
- If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.
- If the cause is not visually evident, verify the symptom and refer to the Symptom Chart, alternatively check for Diagnostic Trouble Codes (DTCs) and refer to the relevant DTC Index.