Circuit 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 brake pedal position sensor receives a low reference signal and a 5-volt reference voltage from the body control module (BCM) when the driver applies the brakes. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM 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 BCM 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 P0572 Brake Switch Circuit 1 Low Voltage
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 ground on the signal circuit when the serial data message from the BCM indicates the brakes are applied.
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
Important:
• Verify that the brake pedal position 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
in Wiring Systems.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Exterior Lights Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 | Test the stop lamp switch signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. 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 in Wiring Systems. Did you find and correct the condition? | Go to Step 5 | Go to Step 4 |
4 | Replace the ECM. Refer to Control Module References in Computer/Integrating Systems 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 |
