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

Stop Lamp Switch Signal

B3445, P0573

P0573

P0572

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Circuit/System Description

When the brake pedal is applied, the BCM receives a brake applied signal from the brake pedal position sensor (BPPS). The BCM applies B+ to the stop lamp switch signal circuit. This circuit supplies a B+ signal to the powertrain control module (PCM) (V6), engine control module (ECM) (V8), transmission control module (TCM) (V8), throttle actuator control (TAC) module (V6), and electronic brake control module (EBCM) indicating the brakes are applied. B+ is also supplied to the center high mound stop lamp (CHMSL), illuminating it when the brakes are depressed.

Conditions for Running the DTC

The ignition is ON

Conditions for Setting the DTC

The ECM detects a short to voltage on the stop lamp switch signal circuit while the brakes are not applied

Action Taken When the DTC Sets

    • Stop lamp switch input is ignored. Brake apply status is obtained through serial data messages.
    • Cruise control is disabled

Conditions for Clearing the DTC

    • The condition responsible for setting the DTC no longer exists
    • A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred

Reference Information

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Lighting Systems Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

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

Circuit/System Verification

Ignition ON, depress the brake pedal. The stop lamps should illuminate.

Circuit/System Testing

  1. Ignition OFF, disconnect the C1 harness connector at the ECM.
  2. Connect a test lamp between the signal circuit terminal 7 and ground.
  3. Ignition ON, press and release the brake pedal. The test lamp should turn ON and OFF when pressing and releasing the brake pedal.
  4. If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    If the test lamp is always OFF, test the signal circuit for a short to ground 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.

Control Module References for BCM or ECM replacement, setup, and programming