Cruise Control

DTC P0703

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* 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

Circuit/System Description

The body control module (BCM) monitors the stop lamp switch, mounted on the brake pedal. The BCM sends a GMLAN serial data message to the engine control module (ECM) indicating the status of the stop lamp switch.

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

Ensure all the stop lamps operate properly. Refer to Exterior Lighting Systems Description and Operation to avoid misdiagnosis. If the vehicle stop lamps operate improperly, refer to Symptoms - Lighting. - Symptoms - Lighting

Circuit/System Testing

Important: Repair any Brake System related DTCs before using this diagnostic.

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

1. Verify proper operation of the vehicle stop lamps. refer to Exterior Lighting Systems Description and Operation.

• If the vehicle stop lamps do not operate as described, refer to Symptoms - Lighting. - Symptoms - Lighting

2. Ignition ON, press and release the brake pedal several times. With a scan tool, verify DTC P0703 is not set as current in the ECM.

• If DTC P0703 is current in the ECM, replace the BCM.

3. The system is OK. Clear the history DTC. Do not replace any components.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests