Circuit Description
The brake pedal position sensor is used to sense the action of the driver's application of the brake pedal. The BPP sensor provides an analog voltage signal that will increase as the brake pedal is applied. The BPP sensor receives a low reference signal and a 5-volt reference voltage from the instrument panel module (IPM) when the driver applies the brakes. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the IPM will apply battery voltage to the stop/turn signal voltage supply circuit to illuminate the stop lamps and the center high mounted stop lamp (CHMSL). The IPM also sends a brake pedal position sensor signal to the engine control module (ECM) as well as a serial data message to indicate the application of the brake pedal.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0573 Brake Switch Circuit 1 High Voltage
Conditions for Running the DTC
| • | Crank ignition voltage. |
| • | The engine speed is between 50-6,500 RPM. |
| • | The serial data message is valid. |
| • | The transmission control module indicates that the brake pedal is applied, lasts for 5 seconds. |
| • | The brake pedal sensor indicates brakes released. |
Conditions for Setting the DTC
When the serial data message from the IPM indicates that the brake pedal has been released, the signal detected by the ECM still displays applied. The condition occurs 15 times in 18 sampling, each lasting for 3 seconds.
Action 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
| • | Verify that the BPP sensor is properly calibrated. Refer to Brake Pedal Position Sensor Calibration . |
| • | Test drive the vehicle if a switch or circuit condition cannot be located. An intermittent condition may be duplicated during a test drive. |
| • | Thoroughly inspect the wiring and connectors. An incomplete inspection of the wiring and connectors may result in misdiagnosis causing part replacement with the reappearance of the malfunction. If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections. |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Exterior Lights Schematics Connector End View Reference: Master Electrical Component List | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 | Test the stop lamp switch signal circuit for an open or short to battery voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 5 | Go to Step 3 |
3 | Inspect for poor connections at the engine control module (ECM) harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 5 | Go to Step 4 |
4 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the repair? | Go to Step 5 | -- |
5 |
Does the DTC reset? | Go to Step 2 | System OK |
