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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> Accessories & Equipment >> Communication Devices >> Data Communications >> Diagnostic Information and Procedures >> Scan Tool Does Not Communicate with High Speed GMLAN Device >> Circuit/System Testing

Circuit/System Testing

  1. Test for less than 1.0 ohm between the DLC ground circuit terminal 5 and ground.
    • If greater than the specified range, test the ground circuit for open/high resistance.
  2. Remove the terminator resistor.
  3. Test for 110-130 ohms between the terminals of the resistor.
    • If not within the specified range, replace the resistor.
  4. Connect the terminator resistor.
  5. Ignition OFF, disconnect the harness connector X3 of the BCM.
  6. Test for less than 2 ohms of resistance in the GMLAN serial data circuit between the DLC terminal 6 and BCM terminal 16.
    • If greater than specified, test the GMLAN serial data circuit for open/high resistance.
  7. Ignition OFF, disconnect the harness connector X4 of the BCM.
  8. Verify a test lamp illuminates between each ground circuit terminal of the BCM listed below and B+.
    • X3 terminal 1
    • X3 terminal 5
    • X4 terminal 9
    • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  9. Ignition ON, verify a test lamp illuminates between each B+ circuit terminal of the BCM listed below and ground.
    • X4 terminal 1
    • X4 terminal 3
    • X4 terminal 4
    • If the test lamp does not illuminate, test the B+ circuit for an open/high resistance or short to ground.
  10. Ignition OFF, disconnect the harness connector of the vehicle communication interface module (VCIM).
  11. Test for infinite resistance between the high speed GMLAN serial data circuit of the DLC terminal 6 and ground, and terminal 14 and ground.
    • If less than the specified range, test the serial data circuit for a short to ground.
  12. Ignition ON, test for less than 1 volt between the high speed GMLAN serial data circuit of the DLC terminal 6 and ground, and terminal 14 and ground.
    • If greater than the specified range, test the serial data circuit for a short to voltage.
  13. Test for infinite resistance between the high speed GMLAN serial data circuits of the DLC terminal 6 and 14.
    • If less than the specified range, test the serial data circuits for a short between them.
  14. Connect the harness connectors of the BCM and the VCIM.
  15. Disconnect the harness connector of the air suspension control module (ASCM).
  16. Attempt to communicate with the BCM. Communication should not be available.
    • If communication is established, Test the serial data circuits between the ASCM and the terminator resistor for a short to ground, short to voltage, and a short between them. If the circuits test normal, replace the ASCM.
  17. Ignition OFF, disconnect the harness connector of the fuel pump flow control module (FPCM).
  18. Attempt to communicate with the BCM. Communication should not be available.
    • If communication is established, test the serial data circuits for a short between the circuits, short to voltage, or a short to ground between the FPCM and the ASCM. If the circuits test normal, replace the FPCM.
  19. Ignition OFF, disconnect the harness connector X2 of the electronic brake control module (EBCM).
  20. Attempt to communicate with the BCM. Communication should not be available.
    • If communication is established, test the serial data circuits for a short between the circuits, short to voltage, or a short to ground between the EBCM and the FPCM. If the circuits test normal, replace the EBCM.
  21. Ignition OFF, disconnect the harness connector X1 of the transfer case control module (TCCM).
  22. Attempt to communicate with the BCM. Communication should not be available.
    • If communication is established, test the serial data circuits for a short between the circuits, short to voltage, or a short to ground between the TCCM and the EBCM. If the circuits test normal, replace the TCCM.
  23. Ignition OFF, disconnect the harness connector X1 of the VCIM.
  24. Attempt to communicate with the BCM. Communication should not be available.
    • If communication is established, test the serial data circuits for a short between the circuits, short to voltage, or a short to ground between the VCIM and the TCCM. If the circuits test normal, replace the VCIM.
  25. Ignition OFF, connect the harness connectors of disconnected modules.
  26. Ignition OFF, disconnect the harness connector X1 of the ECM.
  27. Attempt to communicate with the BCM. Communication should not be available.
    • If communication is established, replace the ECM.
  28. Ignition OFF, disconnect the harness connector of the transmission control module (TCM). Attempt to communicate with the BCM. Communication should not be available.
    • If communication is established, test the serial data circuits for a short between the circuits, short to voltage, or a short to ground between the TCM and the ECM. If the circuits test normal, replace the TCM.
  29. Ignition OFF, disconnect the harness connector X3 of the BCM.
  30. Test for infinite resistance between the serial data circuits of BCM terminal 8 and ground, and between BCM terminal 9 and ground.
    • If less than the specified range, test the circuit for a short to ground.
  31. Ignition ON, test for less than 1 volt between the serial data circuits of BCM terminal 8 and ground, and between BCM terminal 9 and ground.
    • If greater than the specified range, test the circuit for a short to voltage.
  32. Test for infinite resistance between the serial data circuits of BCM terminal 8 terminal 9.
    • If less than the specified range, test the serial data circuits for a short between them.
  33. If the circuits test normal, replace the BCM.
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