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 |
