Circuit Description
The brake pedal position sensor is used to sense the action of the driver's 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 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 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 IPM 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
| • | Verify that the Brake Pedal Position sensor is properly calibrated. Refer to Stop Lamp Switch Adjustment . |
| • | 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 a short to ground. 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 |
