GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2008 🢒 XLR 🢒 DTC 🢒 DTC B1451

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC B1451 02: Device Ignition ACCESSORY Circuit Short to Ground

DTC B1451 05: Device Ignition ACCESSORY Circuit Short to Battery

Circuit/System Description

The body control module (BCM) provides an accessory voltage output, enabled in Run and Accessory power modes. The accessory voltage circuit provides power for engine control module (ECM), transmission control module (TCM), the traffic information receiver (U3Z, if equipped), and the wiper run/acc relay.

Conditions for Running the DTC

Voltage supplied to the module is in the normal operating voltage range of 9-16 volts.

Conditions for Setting the DTC
    • The BCM detects a short to ground in the accessory power circuit.
    • The BCM detects a short to battery or an open in the accessory power circuit.

Action Taken When the DTC Sets

The BCM will disable the accessory power output until the next ignition cycle.

Conditions for Clearing the DTC
    • A current DTC clears when the malfunction is no longer present.
    • A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Reference Information

Schematic Reference

    •  Power Distribution Schematics
    •  Wiper/Washer Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

    •  Retained Accessory Power Description and Operation
    •  Power Mode Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing
  1. Ignition OFF, disconnect the wiper run/acc relay.
  2. Verify DTC B1451 is set.
    3. ⇒If DTC is not set, replace the wiper run/acc relay.
  3. Ignition OFF, disconnect the X3 harness connector at the underhood fuse block.
  4. Ignition ON, verify a test lamp illuminates between the underhood fuse block terminal E7 and ground.
    5. ⇒If test lamp does not illuminate, test the accessory voltage circuit for a short to ground or an open/high resistance. If circuit tests normal, replace the BCM.
  5. Ignition OFF, connect the X3 harness connector at the underhood fuse block.
  6. Disconnect the X1 harness connector at the ECM and X400 harness connector at the TCM.
  7. Ignition OFF, verify the a test lamp does not illuminate between the ECM accessory voltage circuit 18 and ground.
    8. ⇒If the test lamp illuminates, test the accessory voltage circuit for a short to voltage. If all circuit tests normal, replace the BCM.
  8. Ignition ON, verify a test lamp illuminates between the ECM accessory voltage circuit terminal 18 and ground.
    9. ⇒If the test lamp does not illuminate, test the following conditions:
    • Accessory voltage circuit for a short to ground or an open/high resistance.
    • Heated seat/wiper relay ignition voltage circuit for a short to ground.
    ⇒If all circuit tests normal, replace the BCM.
  9. Connect the X1 harness connector at the ECM.
  10. Verify DTC B1451 is not set.
    11. ⇒If DTC is set, replace the ECM.
  11. If all circuits test normal, replace the TCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for BCM, TCM, and ECM replacement, setup, and programming