P0572

DTC P0572 or P0573
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 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 B+ 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 B+ on the stop lamp switch 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 engine is running.
Battery voltage is greater than 11.5 V.

Conditions for Setting the DTC
P0572
This DTC will set when the ECM detects a short to ground or an open on the discrete brake signal circuit when the serial data message from the BCM indicates the brakes are applied. This diagnostic will run when the serial data message and the voltage signal on the brake switch signal circuit do not match for 8 out 10 times, and the condition is present for greater than 2 seconds.

P0573
This DTC will set when the ECM detects a short to voltage on the discrete brake signal circuit when the serial data message from the BCM indicates the brakes are NOT applied. This diagnostic will run when the serial data message and the voltage signal on the brake switch signal circuit do not match for 8 out 10 times, and the condition is present for greater than 2 seconds.

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.

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

Scan Tool Reference
Control Module References for scan tool information

Circuit/System Testing
Vehicle OFF, disconnect the X1 harness connector at the K20 ECM.
Connect a test lamp between terminal 33 and ground.
Vehicle in Service Module, 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 K9 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 K9 BCM.

If all circuits test normal, replace the K20 ECM.

Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
Control Module References for BCM or ECM, replacement, programming and setup