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Class 2 Communication Malfunction: Testing

  1. Connect scan tool to DLC. Select DISPLAY DTCs for each module. Record each DTC, DTC status and module stored in. If any DTC between U1000 and U1255 exist with a history status, go to DTC UXXX: LOST COMMUNICATION WITH XXX  . If no DTCs between U1000 and U1255 exist as a history DTC, go to next step. If other DTCs exist, go to appropriate system starting point for related system.
  2. Turn ignition switch to RUN position. Attempt to communicate with each module on Class 2 serial data circuit (PCM, EBCM, SDM, IPC, DIC, Remote CD Player, Radio, Auxiliary Power Connector and BCM). If communication does not exist with any module(s), go to next step. If communication exists with all modules, go to step  11 .
  3. Check positive battery voltage circuits and ignition voltage circuit(s) of module(s) not communicating, for short to ground. Repair as necessary. After repair, go to step  9 . If battery and ignition voltage circuit(s) are okay, go to next step.
  4. Turn ignition switch to OFF position. Check ground circuit(s) of module(s) not communicating, for open or high resistance. Repair as necessary. After repair, go to step  9 . If ground circuit(s) are okay, go to next step.
  5. Disconnect splice pack SP205. Check for poor terminal contact at splice pack harness connector. Repair as necessary. After repair, go to step  9 . If terminal contact is okay, go to next step.
  6. Check class 2 serial data circuit for open between splice pack connector SP205 and module that is not communicating. See appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS. Repair as necessary. After repair, go to step  9 . If class 2 serial data circuits are okay, go to next step.
  7. Check for poor terminal contact at battery voltage, ignition voltage, class 2 serial data and ground circuits of module(s) that are not communicating. Repair terminal connections as necessary. See appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS. If terminal connections are okay, go to next step.
  8. Replace module that is not communicating. Go to appropriate system article for replacement procedures. After repair, go to step  11 .
  9. Connect scan tool to DLC. Turn ignition switch to RUN position. Select DISPLAY DTCs function for module that was communicating. If scan tool does not display any communication DTCs exist (DTCs beginning with a "U"), go to appropriate system diagnostic system check starting point for related system. If any communication DTCs exist, go to next step. If other DTCs exist, go to appropriate system starting point for related system.
  10. Using scan tool, clear all DTCs. Go to next step.
  11. Select DISPLAY DTCs function for module that had U1000 or U1255 set as a current DTC. If scan tool displays any DTCs that do not begin with "U", go to appropriate system diagnostic system check starting point for related system. If no DTCs that begin with "U" exist, clear all DTCs. Go to next step.
  12. Connect scan tool to DLC. Turn ignition switch to RUN position. Clear all DTCs. Turn ignition to OFF position for 5 seconds. Turn ignition switch to RUN position. Select DISPLAY DTCs function. If DTC U1000 or U1255 exists as a current DTC, go to next step. If DTC U1000 or U1255 does not exist as a current DTC, go to DIAGNOSTIC AIDS  .
  13. Replace module that had DTC U1000 or U1255 set as current DTC. Clear DTCs. Retest system.
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