Diagnostic Instructions
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. |
| • | Use the scan tool in order to clear the DTC. |
Diagnostic Aids
Important: Repair any brake system related DTCs before performing this diagnostic.
| • | This DTC may be stored as a history DTC without affecting the operation of the ECM. If stored only as a history DTC and not retrieved as a current DTC, do not replace the BCM or ECM. |
| • | If this DTC is retrieved as both a current and a history DTC, replace the ECM. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Scan Tool Data List
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
.
Circuit/System Testing
Important: Fix 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 BCM or ECM if this DTC is stored only as a history DTC and is not retrieved as a current DTC.
- Ignition ON, perform the brake pedal position (BPP) sensor calibration procedure and verify the BPP is calibrated properly. Refer to
Brake Pedal Position Sensor Calibration
.
| ⇒ | If the BPP will not calibrate properly, replace the BPP. |
- Cycle the ignition, apply and release the brake pedal. Using a scan tool, check for DTC P0703 in the ECM.
| ⇒ | If DTC P0703 sets as current in the ECM, replace the ECM. |
| ⇒ | If DTC P0703 does not set in the ECM, the system is OK. |
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
