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Circuit/System Testing

WARNING: This page is about a different car, the 2009 Buick Lucerne. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connectors at the appropriate control modules listed below.
    • PCM X1 and TAC module (L26)
    • ECM X1 and TCM (LD8)
  2. Connect a test lamp between the appropriate signal circuit terminal listed below and ground.
    • TAC terminal 6 (L26)
    • TCM terminal 42 (LD8)
  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 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 (L26) or the TCM (LD8).
  5. Connect a test lamp between the appropriate signal circuit terminal listed below and ground.
    • PCM terminal 32 X1 (L26)
    • ECM terminal 7 X1 (LD8)
  6. 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 OFF, test the signal circuit for an open/high resistance. If the circuit test normal, replace the TAC module (L26) or the TCM (LD8).
  7. If all circuit tests normal, replace the PCM (L26) or the ECM (LD8).
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