DTC P0572 or P0573. Buick LaCrosse 2008

For 1990-2009 cars only

Makes 🢒 Buick 🢒 2008 🢒 LaCrosse 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P0572 or P0573

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 P0572: Brake Switch Circuit 1 Low Voltage

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	--

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) (L26), or engine control module (ECM) (LS4/LY7), transmission control module (TCM) with (LS4/LY7), and throttle actuator control (TAC) with (L26) module, 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.

•	The engine is running.

•	Battery voltage is greater than 11.5 volts.

Conditions for Setting the DTC

P0572

The ECM/PCM detects a short to ground or an open/high resistance on the stop lamp switch signal circuit while the brakes are applied

P0573

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

Actions Taken When the DTC Sets

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

•	The malfunction indicator lamp (MIL) will not illuminate.

•	The cruise control system is disabled.

Conditions for Clearing the DTC

•	The condition responsible for setting the DTC no longer exists.

•	A history DTC will clear after 100 malfunction-free ignition cycles have occurred.

Reference Information

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Scan Tool Reference

Control Module References for Scan Tool Information

Circuit/System Testing

Ignition OFF, disconnect the harness connectors at the appropriate control modules listed below.

•	ECM X2 module and TCM (LY7)

•	ECM X1 module and TCM (LS4)

•	PCM X1 module and TAC (L26)

Connect a test lamp between the appropriate signal circuit terminal listed below and ground.

•	TAC terminal 6 (L26)

•	TCM terminal 42

Ignition ON, verify the test lamp illuminates ON and OFF while pressing and releasing the brake pedal.

⇒	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.

Ignition OFF, connect the harness connector at the TCM or TAC.
Connect a test lamp between the appropriate signal circuit terminal listed below and ground.

•	ECM terminal 59 (LY7)

•	ECM terminal 29 (LS4)

•	PCM terminal 32 (L26)

Ignition ON, verify the test lamp illuminates ON and OFF while pressing and releasing the brake pedal.

⇒	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 appropriate TCM or TAC.

If all circuits tests normal, replace the appropriate ECM with (LS4/LY7), or PCM with (L26).

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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