brake pedal position switch

The brake pedal position sensor is mounted on the power brake booster in the engine compartment. Its task is to supply the Engine control module (ECM) with information about the position of the brake pedal.

The brake pedal position sensor is affected by the brake pedal push rod and is a sliding potentiometer. The sensor is supplied with 5 V from the engine control module (ECM) and the signal that varies depending on the position of the brake pedal is sent to the engine control module (ECM).

When the pedal is released the signal is 3 - 4.5 V, the precise value depends on the engine control system in the vehicle. The reason that the signal differs between different engine control systems, despite it being the same sensor, is that the control module's internal circuits differ, which affects the signal level from the sensor. When the pedal is depressed, the voltage from the sensor drops.

From model year 2002 the brake pedal position sensor is directly connected to the brake control module (BCM), information is sent over the CAN to the Engine control module (ECM).

The information from the brake pedal position sensor is used: 

• together with information from the stop lamp switch to determine when it is permitted to use cruise control
• to determine whether the information from the stop lamp switch is valid or not.

To determine whether the information from the stop lamp switch can be used or not, the Engine control module (ECM) and the Electronic throttle module (ETM) carry out an electrical check of the circuits and plausibility checks.