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Home >> Cadillac >> 2012 >> Escalade EXT >> Repair and Diagnosis >> External Pages >> Different car >> Section 1807 (Trailer Brake Control System) >> Diagnostic Information and Procedures >> DTC B3894 (Gasoline Without LY6) >> Circuit/System Testing
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Circuit/System Testing

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NOTE:

Diagnose all other brake light DTCs or Symptoms prior to performing this diagnostic procedure.

  1. Verify that DTC B3445, C0277, C0297, or C0890 are not set.
  2. Ignition OFF, disconnect the harness connector at the fuel pump/trailer brake control module.
  3. Ignition ON, test for greater than 11 V between the ignition circuit terminal 15 and ground.
    • If less than the specified range, test the ignition circuit for a short to ground or an open/high resistance. If the circuit test normal and the MISC - IGN fuse is open, test the signal circuit terminal 37 for a short to ground.
  4. Ignition OFF, disconnect the harness at the stop lamp switch.
  5. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal B and ground.
    • If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  6. Ignition OFF, connect the harness connector at the stop lamp switch.
  7. Connect a test lamp between the signal circuit terminal 37 of the trailer brake control module harness connector and ground.
  8. Ignition ON, apply and release the brake pedal, the test lamp should turn ON and OFF when applying 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, test or replace the stop lamp switch.
    • If the test lamp is always OFF, test the signal circuit for an open/high resistance. If the circuit tests normal, test or replace the stop lamp switch.
  9. Ignition OFF, disconnect the X5 harness connector at the body control module (BCM).
  10. Ignition ON, verify a test lamp illuminates between the signal circuit terminal 5 and ground with the brake pedal applied.
    • If the test lamp does not illuminate, test the signal circuit for an open/high resistance.
  11. If all the circuits test normal, replace the fuel pump/trailer brake control module.
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