GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0573: Brake Switch Circuit 1 High Voltage

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Brake Position Sensor Signal

C0277 06

C0277 06

C0277 07

C0277 09

Stop Lamp Relay Control

1

1

1

--

Stop Lamp Switch Signal

P0572, P0719

BP0573, P0719

P0573, P0724

--

Stop Lamp Relay Switch B+

1

1

--

--

Brake Position Sensor 5-Volt Reference

C0870 03

C0870 03

C0870 07

--

Brake Position Sensor Low Reference

--

C0277 06

C0277 07

--

Left Rear Stop/Turn Lamp Supply Voltage

1

1

1

--

Right Rear Stop/Turn Lamp Supply Voltage

1

1

1

--

Center High Mounted Stop Lamp (CHMSL) Ground

--

1

1

--

Rear Stop/Turn Lamp Ground

--

1

1

--

1. Stop Lamps Malfunction

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.

Reference Information

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Lighting Systems Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

    •  Scan Tool Output Controls
    •  Scan Tool Data List
    •  Scan Tool Data Definitions

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

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Brake Pedal Position Sensor Calibration
    •  Control Module References for BCM and ECM replacement, setup, and programming