Test B: No Communication On Class 2 Data Link
- Turn ignition off. Gain access to Body Control Module (BCM), located under upper instrument panel trim panel, behind instrument cluster. See BODY CONTROL MODULE (BCM) under REMOVAL & INSTALLATION. Disconnect BCM. Check for open, short to ground or short to voltage in Purple wire between Light Blue 24-pin BCM connector terminal B9 and Data Link Connector (DLC) terminal No. 2. See Figure and Fig 1
. See DATA LINK CONNECTORS article in WIRING DIAGRAMS. Repair as necessary and retest operation. If Purple wire checks okay, go to next step.
- Reconnect BCM. Disconnect Sensing and Diagnostic Module (SDM), located under rear of center console. Turn ignition on. Using scan tool, attempt to establish communications with BCM. If scan tool is able to communicate with BCM, replace SDM. See appropriate AIR BAG RESTRAINT SYSTEMS article. If scan tool is still unable to communicate with BCM, go to next step.
- Turn ignition off. Reconnect SDM. Disconnect one class-2 module at a time (other than the BCM and SDM). See WIRING DIAGRAMS . Turn ignition on. Using scan tool, attempt to establish communications with BCM. If scan tool is able to communicate with BCM, replace disconnected module. If scan tool is still unable to communicate with BCM, go to next step.
- Check for open, short to ground or short to voltage in serial data line (Purple wire). Repair as necessary and retest operation. If Purple wire checks okay, go to DTC U1064: LOST COMMUNICATIONS WITH BODY CONTROL MODULE under DIAGNOSTIC TESTS.
Courtesy of GENERAL MOTORS CORP.