The stop lamp switch signal circuit is a high voltage input from the instrument panel module (IPM) to the engine control module (ECM), transmission control module (TCM) and the center high mounted stop lamp (CHMSL). The ECM monitors the stop lamp switch circuit to detect when the brake pedal has been applied. The IPM monitors the brake pedal position sensor to determine when the brake pedal is applied. When the brake pedal is applied, the IPM supplies a high voltage signal on the stop lamp switch signal circuit and also sends a serial data message to the ECM indicating that the brake pedal has been applied. The ECM senses a high voltage signal on the stop lamp switch signal circuit when the brake pedal has been applied.

The ECM detects either a low voltage signal on the stop lamp switch signal circuit when the serial data message from the IPM indicates the brakes are applied, or a high voltage signal on the stop lamp switch signal circuit when the serial data message from the IPM indicates the brakes are not applied.

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Cruise Control Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

With a scan tool, command the stop lamps ON and OFF. The stop lamps should turn ON and OFF when changing between the commanded states.

1. Verify that DTC P0572 or P0572 is not set as current.

⇒	If the DTC is set as current, refer to DTC P0572 or P0573

2. Road test the vehicle and attempt to engage cruise. Verify that cruise control engages properly and the DTC P0571 is not set.

⇒	If DTC P0571 sets as current, replace the ECM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming