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Cellular Telephone Module Diagnostic System Check

  1. Connect a scan tool to Data Link Connector (DLC). If scan tool powers up, go to next step. If scan tool does not power up, go to TEST A: SCAN TOOL DOES NOT POWER UP  under SYSTEM TESTS.
  2. Turn ignition on. Try to communicate with cellular telephone module (with RPO UV8) and OnStar(R) Vehicle Interface Unit (VIU). If scan tool communicates with both modules, go to next step. If scan tool does not communicate with both modules, go to TEST B: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE  under SYSTEM TESTS.
  3. Access CLASS 2 POWER MODE in DIAGNOSTIC CIRCUIT CHECK on scan tool. Rotate ignition switch through all positions while observing ignition switch power mode parameter. If ignition switch parameter reading matches ignition switch position for all switch positions, go to next step. If ignition switch parameter reading does not match ignition switch position for all switch positions, go to step TEST C: POWER MODE MISMATCH  under SYSTEM TESTS.
  4. Connect scan tool. Select DISPLAY DTCs function for cellular telephone module (with RPO code UV8) and OnStar(R) Vehicle Interface Unit (VIU). If scan tool displays any DTCs, go to next step. If scan tool does not display any DTCs, repair cellular telephone as necessary.
  5. If scan tool displays any DTCs that begin with a "U", go to next step. If scan tool does not display any DTC's that begin with a "U", go to step  7.
  6. If scan tool displays U1500, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If scan tool does not display U1500, see TEST B: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE  under SYSTEM TESTS.
  7. If scan tool does not display DTCs B1000, B1004, B1007 or B1009, go to next step. If scan tool displays DTC B1000, B1004, B1007 or B1009, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  8. If scan tool displays DTC B1327 or B1328, see DIAGNOSTIC TROUBLE CODE DEFINITIONS in GENERATORS & REGULATORS - DEVILLE article in STARTING & CHARGING SYSTEMS. If scan tool does not display DTC B1327 or B1328, diagnose any other DTCs that exist. See DIAGNOSTIC TROUBLE CODE DEFINITIONS  for information on any other DTCs found.
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