DTC U2106: Lost Communication With TCM
- Perform VEHICLE ON-BOARD DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM. If vehicle on-board diagnostic system check has been performed, go to next step.
- Using scan tool, attempt to establish communication with TCM. If scan tool does not communicate with TCM, go to next step. If scan tool communicates with TCM, go to step 6.
- Check CONTROLS IGN 1 fuse (10-amp) and CONTROLS B+ fuse (10-amp), located in underhood fuse block. See COMPONENT LOCATIONS . If fuses are okay, go to next step. If fuse(s) is blown, replace fuse(s) and check affected circuit(s) for short to ground. See POWER DISTRIBUTION article in WIRING DIAGRAMS. Repair affected circuit as necessary and retest operation.
- Turn ignition off. Disconnect Gray 58-pin TCM connector. See COMPONENT LOCATIONS . Connect test light between ground and TCM harness connector terminals No. 6 (Orange wire) and No. 1 (Pink wire). See Fig 1. If test light illuminates on both circuits, go to next step. If test light does not illuminate on either circuit, repair open in Orange wire between TCM and CONTROLS B+ fuse, or repair open in Pink wire between TCM and CONTROLS IGN 1 fuse. See POWER DISTRIBUTION article in WIRING DIAGRAMS.
- Connect test light between battery voltage and Gray 58-pin TCM connector terminal No. 39 (Black/White wire). If test light illuminates, check for poor connections between ground or underhood fuse block, and TCM. Repair as necessary. If TCM connections are okay, replace TCM. See TRANSAXLE CONTROL MODULE under REMOVAL & INSTALLATION. If test light does not illuminate, repair open in Black/White wire between TCM and ground. See GROUND DISTRIBUTION article in WIRING DIAGRAMS.
- Turn ignition off for 10 seconds. Turn ignition on. Using scan tool, observe scan tool display for DTC U2106 in BCM. If scan tool displays LAST TEST FAILED for DTC U2106 for BCM, go to next step. If scan tool does not display LAST TEST FAILED for DTC U2106 for BCM, problem is intermittent. Check all connections and CAN link circuits for an open. See DATA LINK CONNECTORS article in WIRING DIAGRAMS.
- Turn ignition off. Disconnect Black 64-pin ECM connector J2. Using a DVOM, measure voltage between ground and ECM harness connector J2 terminals No. 45 (Tan/White wire) and No. 61 (Tan wire). If voltage is not 1.5-3.5 volts on either circuit, go to next step. If voltage is 1.5-3.5 volts on both circuits, check connections between ECM and TCM. If connections are okay, replace ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE.
- Check for open in Tan wire (CAN low circuit) or Tan/White wire (CAN high circuit), or for loose connections between ECM and TCM. If circuits and connections are okay, replace TCM. See TRANSAXLE CONTROL MODULE under REMOVAL & INSTALLATION.
Courtesy of GENERAL MOTORS CORP.