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Circuit/System Testing

WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the X1 harness connector at the PCM and the TAC module.
  2. Connect a test lamp between the TAC module harness connector terminal 6 and ground.
  3. Ignition ON, press and release the brake pedal. Verify the test lamp turns ON and OFF when pressing and releasing the brake pedal.
    • If the test lamp is always ON, test the stoplamp switch signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    • If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  4. Ignition OFF, connect the harness connector at the TAC module.
  5. Connect a test lamp between the PCM connector X1 terminal 32 and ground.
  6. Ignition ON, press and release the brake pedal. Verify he test lamp turns ON and OFF when pressing and releasing the brake pedal.
    • If the test lamp is always OFF, test the stoplamp switch signal circuit for an open/high resistance. If the circuit tests normal, replace the TAC module.
  7. If all circuit tests normal, replace the TAC module. Clear the DTC and road test the vehicle. If DTC P1574 resets as current, replace the PCM.
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