Inspection and Verification
- Verify the customer concern.
- Visually inspect the following for obvious signs of mechanical or electrical damage.VISUAL INSPECTION CHART
Mechanical Electrical - Instrument panel dimmer switch
- Smart junction box (SJB) fuse 6 (5A)
- Miniature bulb(s)
- Circuitry
- Delayed accessory relay
- Instrument cluster
- Instrument panel dimmer switch
- Illuminated component(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 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 or the Instrument Cluster 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 .SMART JUNCTION BOX (SJB) DIAGNOSTIC TROUBLE CODE (DTC) INDEX
DTC Description Action B2026 Incandescent Backlighting Output Circuit Failure Go to Pinpoint Test C . B2027 LED Backlighting Output Circuit Failure Go to Pinpoint Test C . All other DTCs - REFER to MULTIFUNCTION ELECTRONIC MODULES article. INSTRUMENT CLUSTER DIAGNOSTIC TROUBLE CODE (DTC) INDEXDTC Description Action U1222 SCP Invalid or Missing Data for Interior Lamps or Missing Data for Tire Pressure Monitoring System (TPMS) OBSERVE the operation of the backlighting intensity and the headlamps command On/Off SCP messages.
If the backlighting intensity and dimming curve operates correctly, REFER to INFORMATION AND MESSAGE CENTER article.
If the backlighting intensity and dimming curve does not operate correctly, go to Pinpoint Test E .All other DTCs - REFER to MULTIFUNCTION ELECTRONIC MODULES article.
NOTE:
Make sure to use the latest scan tool release software.
NOTE:
The vehicle communication module (VCM) LED prove-out confirms voltage and ground from the DLC are provided to the VCM.