Inspection and Verification

Visually inspect for obvious signs of mechanical or electrical damage.

VISUAL INSPECTION CHART

Mechanical	Electrical
Headlamp switch	Wiring, terminals or connectors Light sensor Smart Junction Box (SJB)

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 to use the latest scan tool software release.

If the cause is not visually evident, connect the scan tool to the Data Link Connector (DLC).

NOTE: The Vehicle Communication Module (VCM) LED prove-out confirms power and ground from the DLC are provided to the VCM.

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 power to the scan tool.
If the scan tool does not communicate with the vehicle:
- Verify the ignition is in the ON position.
- The air bag warning indicator prove-out (other indicators may not prove ignition ON) confirm ignition ON. If the ignition does not turn on, refer to STEERING COLUMN SWITCHES article to diagnose no power in RUN.
- Verify the scan tool operation with a known good vehicle.
- Refer to MODULE COMMUNICATIONS NETWORK article to diagnose no response from the 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 DTCs.
Clear the continuous DTCs and carry out the self-test diagnostics for the SJB.
If the DTCs retrieved are related to the concern, refer to DIAGNOSTIC TROUBLE CODE (DTC) CHART . For all other DTCs, refer to the Diagnostic Trouble Code (DTC) Chart in MULTIFUNCTION ELECTRONIC MODULE article.
If no DTCs related to the concern are retrieved, GO to SYMPTOM CHART .