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Home >> Cadillac >> 2012 >> Escalade EXT >> Repair and Diagnosis >> External Pages >> Different car >> Section 1133 (Data Communication System) >> Diagnostic Information and Procedures >> Scan Tool Does Not Communicate with High Speed GMLAN Device >> Circuit/System Testing >> Diagnostic 2
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Diagnostic 2

WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Connect the harness connector at the TCC module.
  2. Ignition OFF, disconnect the harness connector the ECM.
  3. Ignition ON, attempt to communicate with the VCIM. Communication should not be available.
    • If communication is established, replace the ECM.
  4. Ignition OFF, disconnect the harness connector at the transmission control module (TCM).
  5. Ignition ON, attempt to communicate with the VCIM. Communication should not be available.
    • If communication is established, test the following serial data circuits between the ECM and the TCM for a short between the circuits, short to ground or a short to voltage. If the circuits test normal replace the EBCM.
      • Terminal 13
      • Terminal 14
  6. Ignition OFF, disconnect the harness connector at the electronic brake control module (EBCM).
  7. Ignition ON, attempt to communicate with the VCIM. Communication should not be available.
    • If communication is established, test the following serial data circuits between the TCM and the EBCM for a short between the circuits, short to ground or a short to voltage. If the circuits test normal replace the EBCM.
      • Terminal 24
      • Terminal 37
  8. Ignition OFF, disconnect the harness connector at the headlamp leveling module.
  9. Ignition ON, attempt to communicate with the VCIM. Communication should not be available.
    • If communication is established, test the following serial data circuits between the EBCM and the headlamp leveling module for a short between the circuits, short to ground or a short to voltage. If the circuits test normal replace the headlamp leveling module.
      • Terminal 7
      • Terminal 8
  10. Ignition OFF, disconnect the X1 harness connector at the pedestrian impact protection (PIP) module.
  11. Ignition ON, attempt to communicate with the VCIM. Communication should not be available.
    • If communication is established, test the following serial data circuits between the PIP module and the headlamp leveling module for a short between the circuits, short to ground or a short to voltage. If the circuits test normal replace the PIP module.
      • Terminal 35
      • Terminal 37
  12. Ignition OFF, disconnect the X1 harness connector at the TCC module.
  13. Ignition ON, attempt to communicate with the VCIM. Communication should not be available.
    • If communication is established, test the following serial data circuits between the TCC module and the PIP module for a short between the circuits, short to ground or a short to voltage. If the circuits test normal replace the TCC module.
      • Terminal 7
      • Terminal 8
  14. Ignition OFF, disconnect the harness connector at the BCM.
  15. Ignition OFF, test for infinite resistance between the following serial data circuits of BCM and ground.
    • Terminal 8
    • Terminal 9
    • If less than the specified value, test the serial data circuit for a short to ground.
  16. Ignition ON, test for less than 1-volt between the following serial data circuits of BCM and ground.
    • Terminal 8
    • Terminal 9
    • If greater than the specified range, test the serial data circuit for a short to voltage.
  17. Ignition OFF, test for infinite resistance between the BCM serial data circuit terminals 8 and 9.
    • If less than the specified value, test for a short between the serial data circuits.
  18. If all circuits test normal, replace the BCM.
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