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DTC U1000 Or U1255: Class 2 Communication Malfunction: Testing

  1. If any history DTCs in the range of U1001-U1199 exist, perform appropriate diagnostic and repair procedure. See BODY CONTROL MODULE DIAGNOSTIC TROUBLE CODE INDEX  table under SELF-DIAGNOSTIC SYSTEM. If no history DTCs within this range are set, go to next step.
  2. Turn ignition on. Using scan tool, communicate with each module along the class 2 serial data line. Compare modules communicating with scan tool to actual modules along class 2 serial data line. See DATA LINK CONNECTORS article in WIRING DIAGRAMS. If any modules are not communicating, go to next step. If all modules are communicating, go to step  11 .
  3. Check power circuit of non-communicating module for open or short to ground conditions. See POWER DISTRIBUTION article in WIRING DIAGRAMS. If faulty circuit is found, repair as necessary and go to step  9 . If power circuit is okay, go to next step.
  4. Turn ignition off. Check ground circuit for non-communicating module for open condition. See GROUND DISTRIBUTION article in WIRING DIAGRAMS. If faulty circuit is found, repair as necessary and go to step  9 . If circuit is okay, go to next step.
  5. Check for poor connections at power, ground and class 2 circuits at non-communicating module connector. If faulty connection is found, repair as necessary and go to step  7 . If connections are okay, go to next step.
  6. Replace non-communicating module. See appropriate procedure under REMOVAL & INSTALLATION  . After repairs, go to step  9 .
  7. Connect scan tool to Data Link Connector (DLC). Turn ignition on. Select DISPLAY DTCs function for non-communicating module. If any DTCs that do not begin with "U" are present, perform appropriate diagnostic system check. See appropriate diagnostic system check in appropriate article for module that is not communicating. If no DTCs that do not begin with "U" are present, go to next step.
  8. Using scan tool, clear DTCs. Go to next step.
  9. Using scan tool, select DISPLAY DTCs function for non-communicating module that had DTC U1000 or U1255 set as current. If any DTCs that do not begin with "U" are present, perform appropriate diagnostic system check. See appropriate diagnostic system check in appropriate article for module that had a current DTC U1000 or U1255. If no DTCs that do not begin with "U" are present, go to next step.
  10. Using scan tool, clear DTCs. System is okay at this time.
  11. Display DTCs for module that had a current DTC U1000 or U1255. If any other DTCs were present, perform appropriate diagnostic system check. See appropriate diagnostic system check in appropriate article for module that had a current DTC U1000 or U1255. If no other DTCs were present, go to next step.
  12. Using scan tool, clear DTCs, Turn ignition off and wait at least 5 seconds. Turn ignition on. Select DISPLAY DTCs function. If DTC U1000 or U1255 is set as current, go to next step. If DTC U1000 or U1255 is not set as current, go to DIAGNOSTIC AIDS  .
  13. Replace non-communicating module that had DTC U1000 or U1255 set as current. See appropriate procedure under REMOVAL & INSTALLATION  .
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