P0572

DTC P0572 or P0573

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 Descriptors
DTC P0572
- Brake Switch Circuit 1 Low Voltage

DTC P0573
- Brake Switch Circuit 1 High Voltage

Diagnostic Fault Information





Circuit/System Description

The stop lamp switch signal circuit is a high voltage input to the body control module (BCM), engine control module (ECM), transmission control module (TCM), Power Take Off (PTO) module (if equipped) and Trailer Brake controller (if equipped). The BCM monitors the stop lamp switch circuit to detect when the brake pedal has been applied. The ECM monitors the stop lamp switch signal to determine when the brake pedal is applied. When the brake pedal is applied, the BCM 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 switch signal circuit when the stop lamp switch is closed.

Conditions for Running the DTC

* The engine is running.
* Battery voltage is greater than 11.5 volts.

Conditions for Setting the DTC

P0572

The ECM detects a low voltage signal on the stop lamp switch signal circuit for more than 2 seconds when the serial data message from the BCM indicates the brakes are applied. The ECM sets the DTC when the condition has been detected 8 out of 10 times.

P0573

The ECM detects a high voltage signal on the stop lamp switch signal circuit for more than 2 seconds when the serial data message from the BCM indicates the brakes are released. The ECM sets the DTC when the condition has been detected 8 out of 10 times.

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.

Diagnostic Aids

Ensure all the stop lamps operate properly. Refer to Exterior Lighting Systems Description and Operation (Exterior Lighting Systems) to avoid misdiagnosis. If the vehicle stop lamps operate improperly, refer to Symptoms - Lighting (Symptoms - Lighting).

Reference Information
Schematic Reference

* Cruise Control Schematics (Electrical Diagrams)
* Exterior Lights Schematics (Exterior Lights Schematics)

Connector End View Reference

Component Connector End Views (Connector Views)
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)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
2. Ignition ON, test for B+ between the B+ circuit terminal B and ground.

• If less than the specified value, test the B+ circuit for a short to ground or an open/high resistance.

3. Verify the BPP Circuit Signal data parameter displays released.

• If not the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

4. Connect a 3A fused jumper between the B+ circuit terminal B and the signal circuit terminal A. Verify the BPP Circuit Signal data parameter displays applied.

• If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

5. If all circuits test normal, test or replace the stop lamp switch.

Component Testing

1. Ignition OFF, disconnect the stop lamp switch.
2. With the brake pedal released, test for infinite resistance between terminal A and terminal B stop lamp switch.

• If not the specified value, replace the stop lamp switch.

3. With the brake pedal released, test for less than 1.0 ohm between terminal C and terminal D at the stop lamp switch.

• If not the specified value, replace the stop lamp switch.

4. With the brake pedal applied, test for less than 1.0 ohm between terminal A and terminal B at the stop lamp switch.

• If not the specified value, replace the stop lamp switch.

5. With the brake pedal applied, test for infinite resistance between terminal C and terminal D at the stop lamp switch.

• If not the specified value, replace the stop lamp switch.

Repair Instructions

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

* Stop Lamp Switch Replacement (With Adjustable Pedals) (Stop Lamp Switch Replacement (With Adjustable Pedals))Stop Lamp Switch Replacement (Without Adjustable Pedals) (Stop Lamp Switch Replacement (Without Adjustable Pedals))
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming