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Scan Tool Does Not Communicate With Serial Data Line: Testing

  1. If data link communications diagnostic system check has been performed, go to next step. If data link communications diagnostic system check has not been performed, go to DATA LINK COMMUNICATIONS DIAGNOSTIC SYSTEM CHECK  .
  2. Turn ignition off. Connect scan tool to Data Link Connector (DLC). Disconnect bus bars from Black 12-pin star connectors No. 1 and 2. See COMPONENT LOCATIONS  . Connect Serial Data Link Tester (J-42236) to both star connectors. See Fig 1 . Ensure star connectors correctly correspond with serial data link testing connectors No. 1 and 2. Using serial data link tester, put switch in STAR CONNECTOR #1 position. Rotate rotary switch to "M" position. Turn ignition on. Using scan tool, attempt to establish communication with Body Control Module (BCM). If scan tool communicates with BCM, go to next step. If scan tool does not communicate with BCM, go to step  5 .
  3. Ensure switch on serial data link tester is in STAR CONNECTOR #1 position. Using scan tool, attempt to establish communication with the following vehicle systems by rotating rotary switch on serial data link tester as specified:

    • "L"

      Heating, Ventilation and A/C (HVAC) system (W/CJ2 system).

    • "J"

      Remote Function Actuator (RFA) system.

    • "H"

      Real Time Damping (RTD) system (if equipped).

    • "G"

      Instrument Panel Cluster (IPC).

    • "E"

      Traction Control System (TCS).

    • "D"

      Radio system.

    • "B"

      Powertrain Control Module (PCM).

    If scan tool communicates with each system, go to next step. If scan tool does not communicate with each system, go to step  8 .

  4. Turn switch on serial data link tester to STAR CONNECTOR #2 position. Using scan tool, attempt to establish communication with the following vehicle systems by rotating rotary switch on serial data link tester as specified:

    • "C"

      Left Door Control Module (DCM) system.

    • "D"

      Right Door Control Module (DCM) system.

    • "K"

      Seat Control Module (SCM) system (if equipped).

    If scan tool communicates with each system, go to step  10 . If scan tool does not communicate with each system, go to step  8 .

  5. Turn ignition off. Disconnect serial data link tester. Ensure bus bars are still disconnected from star connectors No. 1 and 2. Using DVOM, check continuity of Purple wire between DLC connector terminal No. 2 and star connector No. 1 terminal "A". See WIRING DIAGRAMS  . If continuity exists, go to next step. If continuity does not exist, go to step  11 .
  6. Check continuity between DLC connector terminal No. 2 (Purple wire) and ground. If continuity exists, go to step  11 . If continuity does not exist, go to next step.
  7. Turn ignition on. Using DVOM, check voltage between DLC connector terminal No. 2 (Purple wire) and ground. If any voltage exists, go to step  11 . If no voltage exists, go to next step.
  8. Turn ignition off. Disconnect appropriate system module for system that did not communicate with scan tool. See COMPONENT LOCATIONS  . Using DVOM, check for continuity between appropriate terminal on appropriate star connector and ground. If continuity exists, go to step  12 . If continuity does not exist, go to next step.
  9. Turn ignition on. Using test light connected to ground, probe appropriate terminal on appropriate star connector for system that is not communicating. If test light comes on, go to step  13 . If test light does not come on, go to step  14 .
  10. Check for loose star connector, intermittent short to ground, short to voltage or open in serial data line circuits. If no problem is found, system is operating properly. If problem is found, repair as necessary. After repairs, go to step  15 .
  11. Repair short to ground, short to voltage or open in Purple wire between DLC and star connector No. 1. After repairs, go to step  15 .
  12. Repair short to ground in appropriate wire between unresponsive module and appropriate star connector. After repairs, go to step  15 .
  13. Repair short to voltage in appropriate wire between unresponsive module and appropriate star connector. After repairs, go to step  15 .
  14. Replace appropriate module. After repairs, go to next step.
  15. Turn ignition off. Reinstall all components or connectors. Clear DTCs. Ensure system is operating properly.
Fig 1: Identifying Serial Data Link Tester (J-42236)
G99E08606Courtesy of GENERAL MOTORS CORP.
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