P0703

DTC P0703

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview)provides an overview of each diagnostic category.



DTC Descriptor
DTC P0703 00
- Brake Switch Circuit 2




Circuit/System Description

The body control module (BCM) monitors the brake pedal position sensor. When the brake pedal is applied, the BCM detects a predetermined voltage signal. 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.
* The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records.



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.



Reference Information
Schematic Reference

Cruise Control Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Cruise Control Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning)for Scan Tool Information


Circuit/System Verification

Ignition ON, observe for proper operation of the brake system including the brake lights. Refer to Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation) .


Circuit/System Testing

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



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.



1. Cycle the ignition, apply and release the brake pedal. Using a scan tool, verify that DTC P0703 does not set as current in the ECM.

• If DTC P0703 sets as current in the ECM, replace the ECM.

2. If all circuits test normal, the system is OK. Do not replace the ECM.



Repair Instructions

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


Control Module References (Programming and Relearning)for ECM replacement, setup, and programming