Diagnostic Instructions
DTC Descriptor
DTC P0571: Cruise Control Brake Switch Circuit
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 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 malfunction indicator lamp (MIL) will not illuminate. |
| • | The cruise control system becomes disabled. |
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC not 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
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Ignition ON, observe the Stoplamp Pedal Switch parameter while applying and releasing the brake pedal. The reading should change between Applied/Released, and all brake lights should turn ON and OFF accordingly. Refer to
Exterior Lighting Systems Description and Operation
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
