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Diagnostic Procedures

  1. Turn ignition off. Connect scan tool. Turn ignition on, with engine off. Using scan tool, attempt to establish communication with module. If scan tool communicates with module, go to next step. If scan tool does not communicate with module, go to step 4).
  2. Using scan tool, check for module related DTCs. If any DTC exists, go to next step. If no DTCs exist, system is operating properly.
  3. Check if a Class-II serial data communications related DTCs ("U" codes) are set. If a Class-II DTC is set, go to applicable "U" type code for diagnosis. If other than "U" type DTCs are set, go to appropriate DTC test for diagnosis.
  4. Attempt to establish communication with other modules connected to same serial data line (PCM, RFA, IPC, etc.). If scan tool communicates with the other systems, go to next step. If scan tool does not communicate with the other systems, ensure scan tool is operating properly. If scan tool is okay, check Data Link Connector (DLC) circuit. See WIRING DIAGRAMS  .
  5. Ensure ignition switch is in RUN position. Using a test light connected to ground, probe both sides of BCM power feed fuse. See WIRING DIAGRAMS  . If test light illuminates both circuits, go to next step. If test light does not illuminate on both circuits, go to step 8).
  6. Turn ignition off. Disconnect BCM harness connectors. Turn ignition on. Using a test light connected to ground, probe all module power circuits. See WIRING DIAGRAMS  . If test light illuminates on all circuits, go to next step. If test light does not illuminate on all circuits, go to step 10).
  7. Using a test light connected to battery voltage, probe each BCM module ground circuit. See WIRING DIAGRAMS  . If test light illuminates on all circuits, go to step 11). If test light does not illuminate on all circuits, go to step 9).
  8. Repair open in ignition or battery feed to module power feed fuse. If any fuse is open, locate and repair short in affected circuit. See WIRING DIAGRAMS  . After repairs, go to step 11).
  9. Locate and repair open in module ground circuit. After repairs, go to step 11).
  10. Locate and repair open in module power circuit. After repairs, go to next step.
  11. Turn ignition off. Reinstall all components or connectors. Clear DTCs. See CLEARING DTCS  . After clearing DTCs, ensure system is operating properly. If DTCs are set, go to appropriate DTC diagnostic test.
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