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For 1990-2009 cars only
Makes 🢒 Buick 🢒 2009 🢒 Enclave - AWD 🢒 Driver Information and Entertainment 🢒 Cellular, Entertainment, and Navigation 🢒 DTC P0571

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 Descriptor

DTC P0571: Cruise Control Brake Switch Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Stop Lamp Switch Signal

P0571

P0571

P0571

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Circuit/System Description

The brake applied signal circuit is a high voltage input from the body control module (BCM) to the engine control module (ECM) and transmission control module (TCM). The ECM monitors the stop lamp switch circuit to detect when the brake pedal has been applied. The BCM monitors the brake pedal position sensor to determine when the brake pedal is applied. When the brake pedal is applied, the BCM supplies a high voltage signal on the brake applied signal circuit and also sends a serial data message to the ECM indicating that the brake pedal has been applied. The ECM senses a high voltage signal on the brake applied signal circuit when the brake pedal has been applied.

Conditions for Running the DTC
    • The engine is running.
    • Battery voltage is greater than 11.5 volts.

Conditions for Setting the DTC

The ECM detects either a low voltage signal on the brake applied signal circuit when the serial data message from the BCM indicates the brakes are applied, or a high voltage signal on the brake applied signal circuit when the serial data message from the BCM indicates the brakes are not applied.

Actions Taken When the DTC Sets
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The cruise control system is disabled.

Conditions for Clearing the DTC
    • The condition responsible for setting the DTC no longer exists.
    • A history DTC will clear after 40 malfunction-free ignition cycles have occurred.

Reference Information

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Cruise Control 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 harness connectors at the appropriate control modules listed below.
    2. • ECM X2
    • TCM
  2. Connect a test lamp between the appropriate signal circuit terminal listed below and ground.
    3. • ECM terminal 52
    • TCM terminal 6
  3. Ignition ON, verify the test lamp turns ON and OFF when pressing and releasing the brake pedal.
    4. ⇒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 TCM.
  5. Connect a test lamp between the ECM signal circuit terminal 52 and ground.
  6. Ignition ON, verify the test lamp turns ON and OFF when pressing and releasing the brake pedal.
    7. ⇒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 TCM.
  7. If all circuits test normal, replace the ECM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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