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Cellular Communication Diagnostic System Check

NOTE: The presence of DTCs which begin with "U" indicate some other module on class 2 serial data line is not communicating.
  1. Connect scan tool to Data Link Connector (DLC). DLC is located under left side of instrument panel. 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 switch to RUN position. Attempt to establish communication with Vehicle Interface Unit (VIU). If scan tool communicates with VIU, go to next step. If scan tool does not communicate with VIU, go to TEST B: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE  under SYSTEM TESTS.
    3. NOTE: Engine may start during following step. Turn off engine as soon as crank power mode is observed.
  3. Using scan tool, access class 2 power mode from diagnostic circuit check function. Rotate ignition switch through all positions while observing ignition switch power mode parameter on scan tool. 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 TEST C: POWER MODE MISMATCH  under SYSTEM TESTS.
  4. Using scan tool, select DISPLAY DTCS function and retrieve any VIU DTCs. If scan tool displays any DTCs, go to next step. If scan tool does not display any DTCs, repair cellular communication system as necessary.
  5. If scan tool displays any DTCs which begin with a "U", go to next step. If scan tool does not display any DTCs which begin with a "U", go to step  7.
  6. If scan tool displays DTC U1500, go to DTC U1500  under DIAGNOSTIC TESTS. If scan tool displays any other DTCs, perform appropriate test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  7. If scan tool does not display DTC B1000, B1004, B1007 or B1009, go to next step. If scan tool displays DTC B1000, B1004, B1007 or B1009, perform appropriate test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  8. If scan tool displays DTC B1327 or B1328, repair engine electrical concern. See appropriate GENERATOR & REGULATOR article in STARTING & CHARGING SYSTEMS. If scan tool displays any other DTCs, perform appropriate test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
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