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 Descriptors

DTC P0572 : Brake Switch Circuit 1 Low Voltage
DTC P0573: Brake Switch Circuit 1 High Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Stop Lamp Switch Signal | P0572 P0703 | P0572 P0703 | P0573 P0703 | --

### Circuit/System Description

The stop lamp switch signal circuits are direct hardwire inputs to the engine control module (ECM) The modules monitor the stop lamp switch signal circuit to detect when the brake pedal has been applied. The ECM monitors both switch signal circuits to determine when the brake pedal is applied.

### Conditions for Running the DTC

The ignition is ON.

### Conditions for Setting the DTC

#### P0572

The ECM detects a low voltage signal on the stop lamp switch signal circuit when the brakes are applied.

#### P0573

The ECM detects a high voltage signal on the stop lamp switch signal circuit when the brakes are not applied.

### Action Taken When the DTC Sets

The cruise control system becomes disabled.

### Conditions for Clearing the DTC

The condition responsible for setting the DTC no longer exists.

### 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 Verification

Ignition ON, boserve the BPP Circuit Signal and TCC/Cruise Brake Pedal Switch parameters the readinge should be Released and change to Applied when the brake pedal is pressed.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
2. Verify that a test lamp illuminates between the B+ citcuit terminal 4 and ground.

⇒ | If the test lamp does not illuminate test the B+ cicuit for an open/high resistance or short to ground.

3. Ignition ON, verify that a test lamp illuminates between the ignition citcuit terminal 3 and ground.

⇒ | If the test lamp does not illuminate test the ignition cicuit for an open/high resistance or short to ground.

4. Connect the harness connector at the stop lamp switch.
5. Ignition OFF, disconnect the harness connectors at the ECM.
6. Connect a test lamp between the appropriate brake switch signal circuit terminal and ground.
7. 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 stop lamp switch.

⇒ | 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 stop lamp switch.

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Stop Lamp Switch Replacement

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