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DTC U2100: Can-Bus Communication Malfunction: Testing

  1. Perform appropriate diagnostic system check. See appropriate ENGINE PERFORMANCE article for ECM, appropriate AUTOMATIC TRANSMISSION article for TCM and appropriate ANTI-LOCK/TCS article for EBTCM. After performing diagnostic system check, go to next step.
  2. Test CAN bus high and low circuits for short to ground between ECM and TCM. See appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS. If fault is located and repaired, go to step  15 . If fault is not located and repaired, go to next step.
  3. Test CAN bus high and low circuits for short to ground between ECM and EBTCM. See appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS. If fault is located and repaired, go to step  15 . If fault is not located and repaired, go to next step.
  4. Test CAN bus high and low circuits for short together between ECM and TCM. See appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS. If fault is located and repaired, go to step  15 . If fault is not located and repaired, go to next step.
  5. Test CAN bus high and low circuits for short together between ECM and EBTCM. See appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS. If fault is located and repaired, go to step  15 . If fault is not located and repaired, go to next step.
  6. Test CAN bus high and low circuits for short to voltage between ECM and TCM. See appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS. If fault is located and repaired, go to step  15 . If fault is not located and repaired, go to next step.
  7. Test CAN bus high and low circuits for short to voltage between ECM and EBTCM. See appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS. If fault is located and repaired, go to step  15 . If fault is not located and repaired, go to next step.
  8. Turn ignition off. Reconnect all disconnected modules and any remaining disconnected connectors. Install scan tool to DLC. Turn ignition on. Clear DTCs from ECM, EBTCM and TCM. Turn ignition off. Disconnect TCM and EBTCM. Turn ignition on. Using scan tool, select display DTCs for ECM. If DTC U2100 is set as current, go to next step. If DTC U2100 is not set as current, go to step  10 .
  9. Replace and reprogram ECM. See appropriate ENGINE PERFORMANCE article in ENGINE PERFORMANCE. After replacement and reprogramming, go to step  13 .
  10. Turn ignition off. Reconnect TCM. Turn ignition on. Using scan tool, select display DTCs for ECM and TCM. If DTC U2100 is set as current in ECM or TCM, go to next step. If DTC U2100 is not set as current in ECM or TCM, go to step  12 .
  11. Replace TCM. See appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS. After replacement, go to step  13 .
  12. Replace EBTCM. See appropriate ANTI-LOCK/TCS article in BRAKES. After replacement, go to next step.
  13. Turn ignition off. Reconnect all disconnected modules. Install scan tool to DLC. Turn ignition on. Using scan tool, select display DTCs for ECM, EBTCM and TCM. If any DTCs beginning with U21XX is set as current, go to next step. If any DTCs not beginning with U21XX is set as current, go to step  15 .
  14. If scan tool displayed any DTCs beginning with U21XX as current, go to BODY CONTROL MODULE (BCM) DTC DEFINITIONS  table and perform diagnostic test for that DTC. After fault has been located and repaired, go to next step.
  15. Using scan tool, clear DTCs. See CLEARING DTCS  under SELF-DIAGNOSTIC SYSTEM. After clearing DTCs, go to next step.
  16. Operate vehicle within conditions to set DTC. If DTC U2100 resets, return to step  1 . If DTC U2100 does not reset, system is okay.
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