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Circuit/System Testing

WARNING: This page is about a different car, the 2007 Cadillac SRX. However, it is still accessible from the selected car via links, so may be relevant.

High Speed GMLAN Initial Test

  1. Ignition OFF, test for less than 1.0 ohm of resistance between the data link connector (DLC) ground circuit terminal 5 and ground.

    If greater than the specified range, test the ground circuit for an open/high resistance.

  2. Disconnect the 2nd and 3rd combs from the SP200 splice pack.
  3. Install 3 amp fused jumper wires between the following SP200 terminals.
    • Terminal 21 and terminal 22
    • Terminal 32 and terminal 33
    • Terminal 12 and terminal 16
  4. Ignition ON, attempt to communicate with the electronic suspension control module (ESC).

    If communication is established refer to DIAGNOSTIC 2.

    If communication is not established, refer to DIAGNOSTIC 1.

DIAGNOSTIC 1

  1. Connect the SP200 splice pack connector
  2. Remove the terminator resistor located in the right rear cargo area.
  3. Test for 108-132 ohms of resistance between terminals A and B of the terminator resistor.

    If not within the specified range, replace the resistor.

  4. Connect the harness connector at the terminator resistor
  5. Ignition OFF, disconnect the C3 harness connector at the BCM.
  6. Ignition OFF, test for less than 2 ohms of resistance between the DLC serial data circuit terminal 6 and BCM serial data circuit terminal 8.

    If greater than the specified range, test the serial data circuit for open/high resistance.

  7. Ignition OFF, disconnect the C2 and C4 harness connectors at the BCM.
  8. Test for less than 5 ohms of resistance between the following ground circuit terminals and ground.
    • C3 terminal 1
    • C3 terminal 5
    • C4 terminal 9

    If greater than the specified range, test the ground circuit for an open/high resistance.

  9. Ignition ON, verify a test lamp illuminates between the following B+ circuit terminals and ground.
    • C2 terminal 2
    • C3 terminal 2
    • C3 terminal 3
    • C4 terminal 1
    • C4 terminal 2
    • C4 terminal 3
    • C4 terminal 4
    • C4 terminal 10

    If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, also test the B+ output circuits for a short to ground.

  10. Ignition OFF, test for infinite resistance between the following serial data circuits of the DLC and ground.
    • Terminal 6
    • Terminal 14

    If less than the specified value, test the serial data circuits for a short to ground.

  11. Ignition ON, test for less than 1-volt between the following serial data circuits of the DLC and ground.
    • Terminal 6
    • Terminal 14

    If greater than the specified range, test the serial data circuit for a short to voltage.

  12. Ignition OFF, test for infinite resistance between the DLC serial data circuit terminal 6 and terminal 14

    If less than the specified value, test for a short between the serial data circuits.

  13. Connect the C2, C3 and C4 harness connector at the BCM.
  14. Connect the harness connector at the TCM
  15. Ignition OFF, disconnect the harness connector of the ESC module.
  16. Ignition ON, attempt to communicate with the TCM. Communication should not be available.

    If communication is established, remove the terminator resistor and test the following serial data circuits between the ESC module and the terminator resistor for a short between the circuits, short to ground or a short to voltage. If the circuits test normal, replace the ESC module.

    • ESC module terminal 24
    • ESC module terminal 25
    • ESC module terminal 24 and terminal 25
  17. Ignition OFF, disconnect the C2 harness connector of the vehicle communication interface module (VCIM).
  18. Ignition ON, attempt to communicate with the TCM. Communication should not be available.

    If communication is established, test the following serial data circuits between the VCIM and the ESC module for a short between the circuits, short to ground or a short to voltage. If the circuits test normal, replace the VCIM.

    • VCIM terminal 3
    • VCIM terminal 4
    • VCIM terminal 3 and terminal 4
  19. Ignition OFF, disconnect the C3 harness connector at the BCM.
  20. Ignition OFF, test for infinite resistance between the following serial data circuits and ground.
    • Terminal 16
    • Terminal 17

      • If greater than the specified range, test the serial data circuit for a short to voltage.

  21. Ignition ON, test for less than 1-volt between the following serial data circuits and ground.
    • Terminal 16
    • Terminal 17

      • If greater than the specified range, test the serial data circuit for a short to voltage.

  22. Ignition OFF, test for infinite resistance between the serial data circuit terminal 16 and terminal 17.

    If less than the specified value, test for a short between the serial data circuits.

  23. If the circuits test normal, replace the BCM.

DIAGNOSTIC 2

  1. Connect the SP200 splice pack connector
  2. Ignition OFF, disconnect the appropriate harness connector listed below at the ECM.
    • RPO LY7 - C2
    • RPO LH2 - C3
  3. Ignition ON, attempt to communicate with the TCM. Communication should not be available.

    If communication is established, replace the ECM.

  4. Ignition OFF, disconnect the harness connector at the electronic brake control module (EBCM).
  5. Ignition ON, attempt to communicate with the TCM. Communication should not be available.

    If communication is established, test the following serial data circuits between the ECM and the EBCM for a short between the serial data circuits, short to ground or a short to voltage. If the circuits test normal replace the EBCM.

    • EBCM terminal B12
    • EBCM terminal B9
    • EBCM terminal B12 and terminal B9
  6. Ignition OFF, disconnect the harness connector at the TCM
  7. Ignition OFF, test for infinite resistance between the following serial data circuits of TCM and ground.
    • RPO LY7 - Terminal F20
    • RPO LY7 - Terminal F21
    • RPO LH2 - Terminal 13
    • RPO LH2 - Terminal 14

      • If less than the specified value, test the serial data circuit for a short to ground.

  8. Ignition ON, test for less than 1-volt between the following serial data circuits of TCM and ground.
    • RPO LY7 - Terminal F20
    • RPO LY7 - Terminal F21
    • RPO LH2 - Terminal 13
    • RPO LH2 - Terminal 14

    If greater than the specified range, test the serial data circuit for a short to voltage.

  9. Ignition OFF, test for infinite resistance between the following serial data circuit terminals.
    • RPO LY7 - Terminal F20 and terminal F21
    • RPO LH2 - Terminal 13 and terminal 14

    If less than the specified value, test for a short between the serial data circuits.

  10. If all circuits test normal, replace the TCM.
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