P0572

DTC P0572 or P0573

Diagnostic Instructions

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

DTC Descriptor

DTC P0572 00
- Brake Switch Circuit 1 Low Voltage

DTC P0573 00
- Brake Switch Circuit 1High Voltage

Diagnostic Fault Information






Circuit/System Description

The TCC Brake 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 TCC Brake 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 00

The ECM detects a low voltage signal on the TCC brake 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 00

The ECM detects a high voltage signal on the TCC brake 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.

Action Taken When the DTC Sets

* The cruise control system becomes inoperative.
* The ECM stores the DTC to memory.
* The ECM will record the operating conditions at the time the diagnostic failed. The ECM stores this information in Failure Records.

Conditions for Clearing the DTC

* The condition for setting the DTC no longer exists.
* A history DTC will clear once 40 malfunction-free ignition cycles have occurred.

Diagnostic Aids

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

Circuit/System Testing

1. Disconnect the harness connector of the stop lamp switch.
2. Ignition ON, test for B+ between the stop lamp switch connector terminal B and ground.

^ If the reading is less than specified, test the supply circuit for a short to ground or an open/high resistance.

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

^ If the parameter displays applied, test the TCC Brake signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

4. Connect a 3 amp fused jumper between stop lamp switch harness terminals A and B. Verify the BPP Circuit Signal data parameter displays applied.

^ If the parameter displays released, test the TCC Brake 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

Stop Lamp Switch Test
1. Ignition OFF, disconnect the stop lamp switch.
2. With the brake pedal released, test for infinite resistance between terminals A and B of the switch.

^ If resistance is not as specified, replace the stop lamp switch.

3. With the brake pedal released, test for less than 1.0 ohm resistance between terminals C and D of the switch.

^ If resistance is not as specified, replace the stop lamp switch.

4. With the brake pedal applied, test for less than 1.0 ohm resistance between terminals A and B of the switch.

^ If resistance is not as specified, replace the stop lamp switch.

5. With the brake pedal applied, test for infinite resistance between terminals C and D of the switch.

^ If resistance is not as specified, replace the stop lamp switch.

Repair Instructions

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

* Stop Lamp Switch Replacement.
* Refer to Programming and Relearning. Programming and Relearning