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DTC P0571

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 00

Brake Switch Circuit 1 Malfunction

Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Stop Lamp Switch Signal

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P0571 00



Circuit/System Description

The stop lamp switch signal circuit is direct hardwire inputs to the engine control module (ECM) and the electronic brake control module (EBCM). The ECM monitor the stop lamp switch signal circuit to detect when the brake pedal has been applied. If the ECM detects the brake pedal signal is too high or too low for a period of time, a DTC will set.

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 s.

Action Taken When the DTC Sets

DTC P0571 00 is a type C DTC.

Conditions for Clearing the DTC

DTC P0571 00 is a type C DTC.

Reference Information

Schematic Reference

Cruise Control 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


DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, observe the Brake Lamps Command parameter while applying and releasing the brake pedal. The reading should change between Active/Inactive, and all brake lights should turn ON and OFF accordingly.

Circuit/System Testing


1. Ignition OFF, disconnect the harness at the B22 Brake Pedal Position Sensor.

2. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal A and ground.

3. If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace K9 Body Control Module.

4. If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.

5. Test for 4.8-5.2 V between the 5 V reference circuit terminal A and the low reference circuit terminal C.

6. If the value is less than the specified range, test the low reference circuit for an open circuit/high resistance. If the circuit tests normal, replace K9 Body Control Module.

7. If greater than the specified range, test the low reference circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.

8. Verify the scan tool Brake Lamps Command parameter is INACTIVE.

9. If the Brake Lamps Command parameter is ACTIVE, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.

10. Install a 3 A fused jumper wire between the 5 V reference circuit terminal A and the signal circuit terminal B. Verify the scan tool Brake Lamps Command parameter is ACTIVE.

11. If the Brake Lamps Command parameter is INACTIVE, test the signal circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.

12. If all circuits test normal, replace the B22 Brake Pedal Position Sensor.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control module replacement, setup and programming