DTC P0572 or P0573. Buick Lucerne 2009

For 1990-2009 cars only

Makes 🢒 Buick 🢒 2009 🢒 Lucerne 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 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 Descriptors

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	P0572, P1574,	P0572, P1574	P0573	--

The stop lamp switch signal circuit is a direct hardwire input from the body control module (BCM) to the engine control module (ECM), powertrain control module (PCM), transmission control module (TCM) and throttle actuator control (TAC) module (L26). The modules monitor the stop lamp switch signal circuit to detect when the brake pedal has been applied. When the brake pedal is applied, the BCM sends a serial data message to the modules and also a voltage signal on the stop lamp switch signal circuit indicating that the brake pedal has been applied.

Conditions for Running the DTC

•	The engine is running.

•	Battery voltage is greater than 11.5 volts.

Conditions for Setting the DTC

P0572

The ECM/PCM detects a low voltage signal on the stop lamp switch signal circuit when the serial data message from the BCM indicates the brakes are applied.

P0573

The ECM/PCM detects a high voltage signal on the stop lamp switch signal circuit when the serial data message from the BCM indicates the brakes are not applied.

Actions Taken When the DTC Sets

•	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 40 malfunction-free ignition cycles have occurred.

Reference Information

Schematic Reference

•	Exterior Lights Schematics

•	Cruise Control Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Cruise Control Description and Operation

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.

•	PCM X1 and TAC module (L26)

•	ECM X1 and TCM (LD8)

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

•	TAC terminal 6 (L26)

•	TCM terminal 42 (LD8)

Ignition ON, press and release the brake pedal. Verify the test lamp turns ON and OFF when 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 TAC module (L26) or the TCM (LD8).
Connect a test lamp between the appropriate signal circuit terminal listed below and ground.

•	PCM terminal 32 X1 (L26)

•	ECM terminal 7 X1 (LD8)

Ignition ON, press and release the brake pedal. Verify the test lamp turns ON and OFF when pressing and releasing the brake pedal.

⇒	If the test lamp is always OFF, test the signal circuit for an open/high resistance. If the circuit test normal, replace the TAC module (L26) or the TCM (LD8).

If all circuit tests normal, replace the PCM (L26) or the ECM (LD8).

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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