Circuit Description
The body control module (BCM) monitors the BPP sensor and sends brake signals to the transmission control module (TCM) via a discreet circuit indicating the status of the stop lamps. The BCM also sends brake signals via the GMLAN serial data circuit to the TCM indicating the status of the stop lamps. When the TCM detects a missing or an invalid brake signal from the BCM, DTC P0703 sets in the TCM. An invalid brake signal may be a result of a signal mismatch between the stop lamp discreet circuit and the GMLAN serial data circuit from the BCM.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
| • | The TCM detects a missing or invalid brake signal from the BCM. |
| • | This diagnostic runs continuously. |
Action Taken When the DTC Sets
| • | Autograde braking inhibited. |
| • | The cruise control system is disabled. |
| • | The TCM stores the DTC information into memory when the diagnostic runs and fails. |
| • | The TCM records the operating conditions at the time the diagnostic fails. The TCM stores this information in the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The DTC becomes history when the fault is no longer present. |
| • | A History DTC clears after 100 malfunction free ignition cycles. |
| • | Use the scan tool in order to clear the DTC. |
Diagnostic Aids
| • | If a BCM has been replaced, the brake pedal position (BPP) sensor must be calibrated. Refer to Brake Pedal Position Sensor Calibration in Lighting System. |
| • | This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module. |
| • | For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Test Description
The numbers below refer to the step numbers located in the diagnostic table.
-
This step is performed in order to confirm that DTC P0703 is current within the ECM.
-
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 Engine Control Module Connector End Views in Engine Controls - 4.6 L or Computer/Integrating Systems Connector End Views in Computer/Integrating Systems or Antilock Brake System Connector End Views in Antilock Brake System | |||
1 |
Important: Repair all DTCs related to the stop lamps and to the brake system before performing this table. Did you perform the Cruise Control Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
Is DTC P0703 current in the PCM? | 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 BCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 6 | Go to Step 5 |
5 |
Important: Program the replacement BCM. The BPP sensor must be calibrated after replacement. Replace the BCM. Refer to Body Control Module Replacement in Computer/integrating Systems. Did you complete the replacement? | Go to Step 6 | -- |
6 |
Does the DTC reset? | Go to Step 2 | System OK |
