P0573

DTC P0573

DTC Descriptor
DTC P0573
- Brake Switch Circuit 1 High Voltage

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview






Circuit/System Description

The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor provides an analog voltage signal that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5-volt reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery positive voltage to the stop lamps, transmission control module (TCM), engine control module (ECM), and stop lamp relay coil side. The BCM also supplies the stop lamp relay coil with ground. When the stop lamp relay receives battery voltage and ground from the BCM, the relay coil is energized and the stop lamp relay switch contacts close applying battery voltage through the STOP/B/U/LPS fuse to illuminate the center high mounted stop lamp (CHMSL).

Conditions for Running the DTC

* The ignition is in the ON position.
* Battery voltage greater than 11.5 volts.

Conditions for Setting the DTC

The ECM detects a short to voltage on the signal circuit when the serial data message from the BCM indicates the brakes are not applied.

Actions Taken When the DTC Sets

* The ECM stores the DTC to memory.
* The ECM will record the operating conditions at the time the diagnostic failed. The ECM stores this information in Failure Records.

Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists.
* You issue a scan tool CLEAR DTCs command.
* A history DTC will clear once 40 malfunction free ignition cycles have occurred.

Diagnostic Aids

Important: The stop lamps will not illuminate unless the ignition is in the ON position. For more detailed information concerning stop lamp operation, refer to Exterior Lighting Systems Description and Operation.

Verify that the brake pedal position sensor is properly calibrated.

Circuit/System Testing

1. Ignition OFF, disconnect the C1 harness connector at the ECM.
2. Connect a test lamp between stop lamp switch signal circuit and ground.
3. Ignition ON, command the stop lamp relay control ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

• If the test lamp is always ON, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

4. If all circuits test normal, replace the ECM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Brake Pedal Position Sensor Calibration.
* Refer to Programming and Relearning. Programming and Relearning