P0571

DTC P0571

Diagnostic Instructions

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

DTC Descriptor
DTC P0571
- Cruise Control Brake Switch Circuit

Diagnostic Fault Information





Circuit/System Description

The stop lamp switch signal circuit is a voltage input from the body control module (BCM) to the engine control module (ECM). 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 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.

Conditions for Running the DTC

* The vehicle has cycled from 0-60 km/h (0-37 mph) 3 times in 1 ignition cycle.
* Continuous once the previous criteria have been met.

Conditions for Setting the DTC

This DTC will set if the serial data message and the voltage signal on the discrete brake signal circuit do not match for 10 consecutive times when this diagnostic is run. This condition must be present for greater than 2 seconds.

Actions Taken When the DTC Sets

DTC P0571 is a type C DTC.

Conditions for Clearing the DTC

DTC P0571 is a type C DTC.

Reference Information
Schematic Reference

Cruise Control Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

Cruise Control Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing For Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference

Control Module References (Programming and Relearning) 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.

Circuit/System Testing

1. Ignition OFF, disconnect the appropriate harness connector listed below at the ECM:

* X1 (L99/LS3)
* X2 (LLT)

2. Connect a test lamp between the appropriate signal circuit terminal listed below and ground:

* Terminal 9 (L99/LS3)
* Terminal 52 (LLT)

3. Ignition ON, press and release the brake pedal. Verify the test lamp turns ON and OFF when pressing 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, 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. If all circuits test normal, replace the ECM.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

Control Module References (Programming and Relearning) for BCM or ECM replacement, setup, and programming