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 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 direct hardwire input from the body control module (BCM) to the engine control module (ECM) and the transmission control module (TCM). The modules monitor the stop lamp switch signal circuit to detect when the brake pedal has been applied. The BCM monitors the brake apply sensor signal circuit to determine when the brake pedal is applied. When the brake pedal is applied, the BCM sends a serial data message to the modules and also a voltage signal on the stop lamp switch signal circuit indicating that the brake pedal has been applied.

Conditions for Running the DTC

* The ignition is ON.
* 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 when the serial data message from the BCM indicates the brakes are applied.

P0573

The ECM detects 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.

Action Taken When the DTC Sets

* 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.
* The cruise control system becomes inoperative.

Conditions for Clearing the DTC

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

Circuit/System Testing

1. Ignition OFF, disconnect the harness connectors at the control modules ECM X1 and TCM.
2. Connect a test lamp between the TCM harness connector terminal 42 and ground.
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. Ignition OFF, connect the harness connector at the TCM.
5. Connect a test lamp between the appropriate signal circuit terminal listed below and ground.

* ECM terminal 9 X1 (with LZE/LZ4/LZ8)
* ECM terminal 7 X1 (with LS4)

6. 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 OFF, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the TCM.

7. If all circuit tests normal, replace the ECM.

Repair Instructions

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