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DTC U1000 Or U1255: Class 2 Communication Malfunction: Testing

  1. If any history DTCs between DTC U1001 and U1199 are present, go to DTC U1001-U1254: LOSS OF XXX COMMUNICATION . If no history DTCs between DTC U1001 and U1199 are present, go to next step.
  2. Turn ignition on. Using scan tool, attempt to communicate with each module on class 2 serial data line. See DATA LINK CONNECTORS article in WIRING DIAGRAMS. If scan tool does not communicate with one or more modules, go to next step. If scan tool communicates with all modules, go to step  13.
  3. Check power circuits for 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 circuits are 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. Disconnect splice pack SP205. Inspect splice pack SP205 for poor connections. Repair as necessary and go to step  9. If splice pack is okay, go to next step.
  6. Check for open in class 2 serial data line for non-communicating module. See DATA LINK CONNECTORS article in WIRING DIAGRAMS. Repair circuit as necessary and go to step  9. If circuit is okay, go to next step.
  7. Check for poor connections at power and ground circuits at harness connector for non-communicating module. Repair connector as necessary and go to step  9. If connector is okay, go to next step.
  8. Replace non-communicating module. See appropriate procedure under REMOVAL & INSTALLATION. Go to step  11.
  9. Connect scan tool to DLC. Turn ignition on. Select display DTCs function for non-communicating module. If scan tool displays any DTCs that do not begin with a "U", perform appropriate diagnostic system check. See appropriate article for malfunctioning system. If scan tool does not display any DTCs that do not begin with a "U", go to next step.
  10. Using scan tool, clear DTCs. Go to next step.
  11. Select display DTCs function for module that had DTC U1000 or U1255 set as current. If scan tool displays any DTCs that do not begin with a "U", perform appropriate diagnostic system check. See appropriate article for malfunctioning system. If scan tool does not display any DTCs that do not begin with a "U", go to next step.
  12. Using scan tool, clear DTCs. System is okay.
  13. If any other DTCs are present, perform appropriate diagnostic system check. See appropriate article for malfunctioning system. If no other DTCs are present, go to next step.
  14. Connect scan tool to DLC. Turn ignition on. 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 .
  15. Replace module that had DTC U1000 or U1255 set as current. See appropriate procedure under REMOVAL & INSTALLATION. System is okay.
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