For 1990-2009 cars

### 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 P0572: Brake Switch Circuit 1 Low Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open or High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Stop Lamp Switch Signal | P0572 | P0573 | P0573 | --

### Circuit/System Description

The brake pedal position sensor (BPP) is used to sense the action of the driver application of the brake pedal. The BPP provides an analog voltage signal that will increase as the brake pedal is applied. The BPP receives a low reference signal and a 5-volt reference voltage from the body control module (BCM) when the driver applies the brakes. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery voltage to the stop/turn signal voltage supply circuit to illuminate the stop lamps and the center high mounted stop lamp (CHMSL). The BCM also sends a BPP signal to the engine control module (ECM) as well as a serial data message to indicate the application of the brake pedal.

### Conditions for Running the DTC

• | The ignition is ON.

• | Battery voltage is greater than 11.5 volts.

### Conditions for Setting the DTC

The ECM detects a short to ground on the stop lamp switch signal circuit when the serial data message from the BCM indicates the brakes are 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.

### Conditions for Clearing the DTC

• | The condition responsible for setting the DTC no longer exists.

• | You issue a scan tool CLEAR DTCs command.

• | A history DTC will clear once 40 malfunction-free ignition cycles have occurred.

### Diagnostic Aids

Verify that the BPP is properly calibrated.

### Reference Information

#### Schematic Reference

Exterior Lights Schematics

#### Connector End View Reference

Lighting Systems Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Output Controls

• | Scan Tool Data List

• | Scan Tool Data Definitions

### Circuit/System Testing

1. With a scan tool, recalibrate the BPP, clear all DTCs, and operate the vehicle within the Conditions for Running the DTC.

⇒ | If DTC P0572 resets as current, test the stop lamp switch signal circuit for a short to ground.

2. If circuits test OK, replace the ECM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Brake Pedal Position Sensor Replacement

• | Control Module References for ECM replacement, setup, and programming

• | Brake Pedal Position Sensor Calibration