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 P0571: Brake Switch Circuit 1

### Circuit/System Description

The stop lamp switch signal circuit is a direct hardwire input to the engine control module (ECM) from the brake switch assembly. The ECM monitors the stop lamp switch signal circuit in order to detect when the brake pedal has been applied.

### Conditions for Running the DTC

Engine is running.

### Conditions for Setting the DTC

• | Brake switch active and vehicle speed is greater than 90 km/h.

• | Brake switch is not active when the brake light switch active for 20 seconds.

• | Vehicle deceleration without brake light switch active for 4 seconds.

### Action Taken When the DTC Sets

• | The Service Vehicle Soon (SVS) Lamp will be illuminated as soon as the error occurs.

• | The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in Failure Records buffers.

• | A history DTC is stored.

### Conditions for Clearing the DTC

• | The SVS lamp will turn off after current driving cycle in which the diagnostic runs without a fault.

• | A history DTC will clear after 20 consecutive warm-up cycles without a fault.

• | DTCs can be cleared by using the scan tool

• | Disconnecting the ECM battery feed for 10 seconds.

### Diagnostic Aids

In order to avoid a misdiagnosis, inspect for proper operation of the stop lamps.

### Reference Information

#### Schematic Reference

Cruise Control Schematics

#### Connector End View Reference

Cruise Control Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

### Circuit/System Testing

1. Apply the brake pedal to test that the stop lamps operate properly?

⇒ | If the brake lamps do not turn on while the brake pedal is depressed, refer to Diagnostic Starting Point - Lighting Systems .

2. Test the stop lamp switch signal circuit for an open or for a high resistance between the brake switch and the engine control module (ECM).
3. Inspect for poor connections at the harness connector of the ECM.
4. If no problems found, replace the ECM.
5. Use the scan tool in order to clear the DTCs. Operate the vehicle within the conditions for running the DTC and verify that the DTC does not reset.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement and programming