Inspection and Verification
- Verify the customer concern.
- Verify the exterior lighting system of the vehicle is operating correctly. If not, refer to the appropriate pinpoint test.
- Visually inspect the following for obvious signs of electrical damage.VISUAL INSPECTION CHART
Electrical - Bussed electrical center (BEC) fuse(s):
- 46 (20A) (trailer tow stop/turn lamp relays)
- 52 (20A) (trailer tow parking lamp relay)
- BEC
- Circuity
- Relay(s)
- Bulb(s)
- Bussed electrical center (BEC) fuse(s):
- 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, connect the scan tool to the data link connector (DLC).
- If the scan tool does not communicate with the VCM:
- Check the VCM connection to the vehicle.
- Check the scan tool connection to the VCM.
- Refer to MODULE COMMUNICATIONS NETWORK article, No Power To The Scan Tool, to diagnose no communication with the scan tool.
- If the scan tool does not communicate with the vehicle:
- Verify the ignition key is in the ON position.
- Verify the scan tool operation with a known good vehicle.
- Refer to MODULE COMMUNICATIONS NETWORK article to diagnose no response from the powertrain control module (PCM).
- Carry out the network test.
- If the scan tool responds with no communication for one or more modules, refer to MODULE COMMUNICATIONS NETWORK article.
- If the network test passes, retrieve and record the continuous memory diagnostic trouble codes (DTCs).
- Clear the continuous DTCs and carry out the self-test diagnostics for the SJB.
- If the DTCs retrieved are related to the concern, go to the Smart Junction Box (SJB) Diagnostic Trouble Code (DTC) Index. For all other DTCs, refer to MULTIFUNCTION ELECTRONIC MODULES article.
- If no DTCs related to the concern are retrieved, go to Symptom Chart .
NOTE:
Make sure the headlamp switch is in the OFF position.
NOTE:
Make sure the multifunction switch is in the LOW BEAM position.
NOTE:
Make sure to use the latest scan tool software release.
NOTE:
The vehicle communication module (VCM) LED prove-out confirms power and ground from the DLC are provided to the VCM.
SMART JUNCTION BOX (SJB) DIAGNOSTIC TROUBLE CODE (DTC) INDEX
| DTC | Description | Action |
|---|---|---|
| B1342 | ECU is Defective | CLEAR the DTCs. RETRIEVE the DTCs. If DTC B1342 is retrieved, INSTALL a new SJB. REFER to MULTIFUNCTION ELECTRONIC MODULES article. TEST the system for normal operation. |
| B2070 | Trailer Tow Relay Coil(s) Circuit Failure | If a trailer lamp is inoperative, go to Pinpoint Test W . If a trailer lamp is always on, go to Pinpoint Test X . |
| All other DTCs | - | REFER to MULTIFUNCTION ELECTRONIC MODULES article. |