2012 Buick VeranoFACTORY OEM SERVICE PROCEDURE

Circuit/System Testing

NOTE:
  • Use the schematic to identify the following:
    • LIN devices the vehicle are equipped with
    • The LIN device's B+, ignition, ground, and serial data circuit terminals
  • Use the Control Module U-Code list to determine which control module is not communicating with the master control module. Refer to Control Module U Code ListΒ .
  • A loss of serial data communications DTC does not represent a failure of the master control module that set it.
  1. Ignition OFF, disconnect the harness connector at a LIN device that is not communicating.
  2. Test for less than 10 Ξ© between each ground circuit terminal and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. If equipped, verify that a test lamp illuminates between each B+ circuit terminal and ground.
    • 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, test the control circuits of the LIN device for a short to ground. If the circuits test normal, replace the LIN device.
  4. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground.
    • If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the LIN device for a short to ground. If the circuits test normal, replace the LIN device.
  5. Ignition ON, test for 2-12 V between the LIN serial data circuit and ground.
    • If greater than the specified range, test the LIN serial data circuit for a short to voltage. If the circuit tests normal, replace the master control module.
    • If less than the specified range, test the LIN serial data circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the master control module.
  6. If all circuits test normal, replace the LIN device.
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.

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