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. |
Reference Information
Schematic Reference
Cruise Control Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References
for scan tool information
Circuit/System Verification
Important:
| • | Repair any brake system related DTCs before using this diagnostic. |
| • | 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, observe for proper operation of the brake system including the brake lights. Refer to
Exterior Lighting Systems Description and Operation
.
- 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 several times. Verify that DTC P0703 is only set as a history code.
| ⇒ | If DTC P0703 sets as current in the ECM, replace the ECM. |
- If the brake system tests normal, clear all codes. The vehicle is OK, do not replace the ECM.
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
