Toyota Tundra Service Manual > Sfi System: Brake Switch "A" / "B" Correlation (P0504)
DESCRIPTION The stop light switch is a duplex system that transmits two signals: STP and ST1-. These two signals are used by the ECM to monitor whether or not the brake system is working properly. If the signals, which indicate the brake pedal is being depressed and released, are detected simultaneo ...
