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 P0703: Brake Switch Circuit 2

### Circuit/System Description

The body control module (BCM) monitors the brake pedal position (BPP) sensor. The BCM sends a GMLAN serial data message to the engine control module (ECM) indicating the status of the stop lamps.

### Conditions for Running the DTC

The engine is ON.

### Conditions for Setting the DTC

• | The ECM receives an invalid brake pedal status GMLAN serial data message from the BCM.

• | This diagnostic runs continuously.

### Action Taken When the DTC Sets

• | The cruise control system is disabled.

• | The ECM stores the DTC information into memory when this diagnostic runs and fails.

• | The malfunction indicator lamp (MIL) will not illuminate.

• | All of the scan tool cruise control function switch parameters are set to Off.

### Conditions for Clearing the DTC

• | A last test failed, or the current DTC, clears when the diagnostic runs and does not fail.

• | A history DTC clears after 40 consecutive warm-up cycles, if failures are not reported by this or any other emission related diagnostic.

• | Use the scan tool in order to clear the DTC.

### Diagnostic Aids

If the BCM has been replaced, the BPP sensor must be calibrated.

### Reference Information

#### Schematic Reference

Cruise Control Schematics

#### Connector End View Reference

Data Communication Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

### Circuit/System Testing

Important:

• | Fix any brake system related DTCs and symptoms before using this diagnostic.

• | Perform the calibration procedure for the BPP sensor.

Important: This DTC may be stored as a history DTC without affecting the operation of the ECM. Do not replace the ECM if this DTC is stored only as a history DTC and is not retrieved as a current DTC.

Ignition ON, verify DTC P0703 is not current in the ECM.

⇒ | If DTC P0703 is current, replace the ECM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming