Initial Inspection and Diagnostic Overview
Inspection and Verification1. Verify the customer concern.
2. Visually inspect for obvious signs of electrical damage.
3. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.
NOTE: Make sure the headlamp switch is in the OFF position.
NOTE: Make sure the multifunction switch is in the low beam position.
4. If the cause is not visually evident, connect the WDS or equivalent Tester to the data link connector and select the vehicle to be tested from the WDS or equivalent Tester menu. If the WDS or equivalent Tester does not communicate with the vehicle:
- check that the program card is correctly installed.
- check the connections to the vehicle.
- check the ignition switch position.
5. If the WDS or equivalent Tester still does not communicate with the vehicle, see the WDS or equivalent Tester operating manual.
6. Carry out the WDS or equivalent Tester data link test. If the WDS or equivalent Tester responds with:
- CAN or ISO circuit fault; all electronic control units no response/not equipped, see COMMUNICATIONS NETWORK.
- No response/not equipped for SJB, see PINPOINT TEST 6: NO MEDIUM SPEED CONTROLLER AREA NETWORK (CAN) COMMUNICATION.
- System passed, retrieve and record the continuous diagnostic trouble codes (DTCs), erase the continuous DTCs and carry out self-test diagnostics for the SJB.
7. If the DTCs retrieved are related to the concern, go to the Smart Junction Box (SJB) Diagnostic Trouble Code (DTC) Index to continue diagnostics. Trailer Lamps
8. If no DTCs related to the concern are retrieved, see SYMPTOM TROUBLESHOOTING CHART. Symptom Related Diagnostic Procedures
- TRAILER LAMPS, to continue diagnostics.
NOTE: When diagnosing the trailer tow lamps, begin by verifying that the vehicle lamp systems are all functioning correctly with the trailer disconnected.
NOTE: For a complete master list of DTCs, see COMMUNICATIONS NETWORK.