Circuit 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.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0703 Brake Switch Circuit 2
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 the 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
| • | Repair any brake system related DTCs before performing this diagnostic. |
| • | If an BCM has been replaced, the brake pedal position (BPP) sensor must be calibrated. Refer to Brake Pedal Position Sensor Calibration. |
| • | This DTC may be stored as a history DTC without affecting the operation of the BCM. If stored only as a history DTC and not retrieved as a current DTC, do not replace the BCM. |
| • | If this DTC is retrieved as both a current and a history DTC, replace the BCM. |
| • | For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections. |
Test Description
The numbers below refer to the step numbers located in the diagnostic table.
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This step is performed in order to confirm that DTC P0703 is current within the ECM.
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This step is performed in order to correct a BPP sensor that must be calibrated, possibly due to a BCM replacement or for a BPP sensor that is out of adjustment.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Cruise Control Schematics Connector End View Reference: Cruise Control Connector End Views or Computer/Integrating Systems Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
Is DTC P0703 current in the engine control module (ECM)? | Go to Step 3 | Go to Diagnostic Aids | |
Does the DTC reset? | Go to Step 4 | System OK | |
4 | Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | Go to Step 6 | Go to Step 5 |
5 | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 6 | -- |
6 |
Does the DTC reset? | Go to Step 2 | System OK |
