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Home >> Pontiac >> 2007 >> G6 Base, 2.4 B >> Repair and Diagnosis >> External Pages >> Different car >> Section 1021 (Data Communication System) >> Diagnostic Information and Procedures >> Scan Tool Does Not Communicate with High Speed GMLAN Device >> Circuit/System Testing
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Circuit/System Testing

WARNING: This page is about a different car, the 2007 Buick Lucerne. However, it is still accessible from the selected car via links, so may be relevant.
  1. With a scan tool verify that communication is not available for all high speed serial data modules.
    • If any high speed module communicates and no DTC beginning with a U exists, Refer to DTC U0100-U0299  for diagnostics
  2. Test for less than 1.0 ohm of resistance between the DLC ground circuit terminal 5 and ground.
    • If greater than 1.0 ohm, test the ground circuit for open/high resistance.
  3. Ignition OFF, disconnect the harness connector of the BCM.
  4. Ignition ON, test for battery voltage between each voltage input circuit of the BCM and ground.
    • If less than battery voltage, test each voltage output circuit of the BCM for a short to ground, and each voltage input circuit of the BCM for a short to ground or and open/high resistance. If the circuits test normal, replace the faulty module.
  5. Test for less than 1 ohm of resistance between each ground circuit of the BCM and ground.
    • If greater than 1 ohm, repair the ground circuit for an open/high resistance.
  6. Remove the terminator resistor located in the rear fuse block.
  7. Attempt to communicate with the EBCM. Communication should not be available.
    • If communication is established, test or replace the resistor.
  8. Ignition OFF, disconnect the harness connector of the suspension control module.
  9. Attempt to communicate with the EBCM. Communication should not be available.
    • If communication is established, test the serial data circuits for a short between them, short to ground or a short to voltage between the suspension control module and the terminator resistor. If the circuits test normal, replace the suspension control module.
  10. Ignition OFF, disconnect the harness connector of the distance sensing cruise control module.
  11. Attempt to communicate with the EBCM. Communication should not be available.
    • If communication is established, replace the cruise control module.
  12. Ignition OFF, disconnect the harness connector of the vehicle communication interface module.
  13. Attempt to communicate with the EBCM. Communication should not be available.
    • If communication is established, test the serial data circuits for a short between them, short to ground or a short to voltage between the between the vehicle communication interface module and the suspension control module. If the circuits test normal, replace the vehicle communication interface module.
  14. Ignition OFF, disconnect BCM harness connector C3.
  15. Test for infinite resistance between the serial data circuits of BCM harness connector C3 terminal 8 and ground and between BCM harness connector C3 terminal 9 and ground.
    • If less than infinite, test the circuit for a short to ground.
  16. Ignition OFF, disconnect the harness connector of the engine control module. Connect the harness connector C3 of the BCM
  17. Attempt to communicate with the EBCM. Communication should not be available.
    • If communication is established, replace the engine control module.
  18. Ignition OFF, disconnect the harness connector of the transmission control module.
  19. Attempt to communicate with the EBCM. Communication should not be available.
    • If communication is established, test the serial data circuits for a short between them, short to ground or a short to voltage between the transmission control module and the engine control module. If the circuits test normal, replace the transmission control module.
  20. Ignition OFF, connect the harness connector of the suspension control module. Disconnect the harness connector of the EBCM.
  21. Attempt to communicate with the suspension control module. Communication should not be available.
    • If communication is established, test the serial data circuits for a short between them, short to ground or a short to voltage between the EBCM and the transmission control module. If the circuits test normal, replace the EBCM.
  22. Ignition OFF, disconnect the harness connector C3 of the BCM.
  23. Test for less than 1 volt between the high speed GMLAN serial data circuits of the DLC and ground.
    • If greater than 1 volt, test the serial data circuit for a short to voltage.
  24. Test for infinite resistance between the high speed GMLAN serial data circuit of the DLC and ground.
    • If less than infinite resistance, test the serial data circuit for a short to ground.
  25. Test for infinite resistance between the high speed GMLAN serial data (+) and (-) circuits of the DLC.
    • If less than infinite resistance, test the serial data circuits for a short between them.
  26. If the circuits test normal, replace the BCM.
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