Diagnostic Instructions
DTC Descriptor
DTC P0571: Cruise Control Brake Switch Circuit
Circuit/System Description
The body control module (BCM) monitors the brake pedal position sensor. When the brake pedal is applied, the BCM detects a predetermined voltage signal. The BCM sends a serial data message to the engine control module (ECM) indicating the status of the
stop lamps.
This diagnostic test functions on the assumption that a sudden decrease in vehicle speed is caused by a brake pedal application. When the ECM detects that there is a 4.2 km/h (2.6 mph) or greater decrease in vehicle speed within 0.25 seconds without a
transition of the stop lamp switch, the ECM sets DTC P0571.
Conditions for Running the DTC
| • | The engine speed is greater than 700 RPM. |
| • | The traction control system or the antilock brake system are not active and have not failed. |
| • | The vehicle speed is greater than 48 km/h (30 mph). |
| • | The diagnostic will disable when the wheel speed is less than 16 km/h (10 mph). |
Conditions for Setting the DTC
The ECM detects either a low voltage signal on the stop lamp switch signal circuit when the serial data message from the BCM indicates the brakes are applied, or a high voltage signal on the stop lamp switch signal circuit when the serial data message
from the BCM indicates the brakes are not applied.
Actions Taken When the DTC Sets
| • | The cruise control system is disabled. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
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
Connector End View Reference
Component Connector End Views
Description and Operation
Cruise Control Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Verify that DTC P0572 or P0573 is not set.
- Verify that DTC P0571 is not set..
| ⇒ | If DTC is set, replace the BCM. Clear the DTC and road test the vehicle. If DTC resets, replace the ECM. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for BCM or ECM replacement, setup, and programming.
