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DTC U2100: Can Bus Communications Malfunction

NOTE: Applies to V6 models only.
  1. 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.
  2. Turn ignition on. Using scan tool, monitor and record all BCM and TCM DTCs. Clear all BCM and TCM DTCs. Turn ignition off for 10 seconds. Turn ignition on. Wait 10 seconds. If BCM sets DTCs U2105 and U2106, and TCM sets DTCs U2105 and U2107, go to next step. If BCM and TCM do not set any "U" type DTCs, problem is intermittent, check CAN link wiring for chafing or broken insulation.
  3. Check CAN low or CAN high for short to voltage or power, or for short between circuits. Access BCM. See COMPONENT LOCATIONS . Connect negative lead of DVOM to ground and backprobe with positive lead to BCM connector J3 terminal A12 (CAN low), and terminal B11 (CAN high). If both voltages are 1.5-3.5 volts, go to next step. If voltage is not between 1.5-3.5 volts, go to step  5.
  4. Check for short between CAN low and CAN high circuits. Turn ignition off. Disconnect Pink 24-pin BCM connector J3, Black 64-pin ECM connector J2 and Gray 58-pin TCM connector. Check continuity between CAN low and CAN high circuits between BCM, ECM and TCM. See WIRING DIAGRAMS . Repair short between appropriate circuits as necessary.
  5. Turn ignition off. Disconnect Black 64-pin ECM connector J2. Turn ignition on. Using a DVOM, measure voltage between ground and ECM harness connector J2 terminals No. 12 (CAN low) and No. 29 (CAN high). If voltage is between 1.5-3.5 volts on both circuits, go to step  8. If voltage is less than 1.5 volt on either circuit, go to step  7. If voltage is more than 3.5 volts on either circuit, go to next step.
    6. NOTE: If one CAN circuit is shorted to voltage, the other CAN circuit voltage will read high.
  6. Check both CAN low and CAN high circuits between BCM and ECM for short to voltage. Turn ignition off. Ensure ECM is disconnected. Disconnect Pink 24-pin BCM connector J3. Turn ignition on. Using a DVOM, measure voltage between ground and BCM harness connector J3 terminal A12 (Tan wire), and terminal B11 (Tan/White wire). See WIRING DIAGRAMS . Repair short to voltage in appropriate circuit as necessary.
    7. NOTE: If one CAN circuit is shorted to ground, the other CAN circuit voltage will read low.
  7. Check both CAN low and CAN high circuits between BCM and ECM for short to ground. Turn ignition off. Ensure ECM is disconnected. Disconnect Pink 24-pin BCM connector J3. Using a DVOM, measure resistance between ground and BCM harness connector J3 terminal A12 (Tan wire), and terminal B11 (Tan/White wire). See WIRING DIAGRAMS . Repair short to ground in appropriate circuit as necessary. If neither circuit is shorted to ground, replace BCM. See BODY CONTROL MODULE  under REMOVAL & INSTALLATION.
  8. Using a DVOM, measure voltage between ground and ECM harness connector J2 terminals No. 45 (CAN high) and No. 61 (CAN low). If voltage is between 1.5-3.5 volts on both circuits, replace ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. If voltage is less than 1.5 volt on either circuit, go to next step. If voltage is more than 3.5 volts, go to step  10.
    9. NOTE: If one CAN circuit is shorted to ground, the other CAN circuit voltage will read low.
  9. Check both CAN low and CAN high circuits between ECM and TCM for short to ground. Turn ignition off. Ensure ECM is disconnected. Disconnect Gray 58-pin TCM connector. Using a DVOM, measure resistance between ground and TCM harness connector terminal 33 (Tan wire), and terminal 34 (Tan/White wire). See WIRING DIAGRAMS . Repair short to ground in appropriate circuit as necessary. If neither circuit is shorted to ground, replace TCM. See TRANSAXLE CONTROL MODULE  under REMOVAL & INSTALLATION.
    10. NOTE: If one CAN circuit is shorted to voltage, the other CAN circuit voltage will read high.
  10. Check both CAN low and CAN high circuits between ECM and TCM for short to voltage. Turn ignition off. Ensure ECM is disconnected. Disconnect Gray 58-pin TCM connector. Using a DVOM, measure voltage between ground and TCM harness connector terminal 33 (Tan wire), and terminal 34 (Tan/White wire). See WIRING DIAGRAMS . Repair short to voltage in appropriate circuit as necessary.
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