Throttle position sensor (TPS)
A throttle position sensor (TPS) is a sensor used to monitor the position of the throttle in an internal combustion engine. The sensor is usually located on the butterfly spindle so that it can directly monitor the position of the throttle. More advanced forms of the sensor are also used, for example an extra closed throttle position sensor (CTPS) may be employed to indicate that the throttle is completely closed. Some engine control units (ECUs) also control the throttle position and if that is done the position sensor is used in a feedback loop to enable that control.
Related to the TPS are accelerator pedal sensors, which often include a wide open throttle (WOT) sensor. The accelerator pedal sensors are used in "drive by wire" systems, and the most common use of a wide open throttle sensor is for the kick-down function on automatic transmissions.
Modern day sensors are non contact type, wherein a magnet and a Hall effect sensor are used. In the potentiometric type sensors, two metal parts are in contact with each other, while the butterfly valve is turned from zero to WOT, there is a change in the resistance and this change in resistance is given as the input to the ECU.
Non contact type TPS work on the principle of Hall effect, wherein the magnet is the dynamic part which mounted on the butterfly valve spindle and the Hall effect sensor is mounted with the body and is stationary. When the magnet mounted on the spindle which is rotated from zero to WOT, there is a change in the magnetic field for the Hall effect sensor. The change in the magnetic field is sensed by the Hall effect sensor and the voltage generated is given as the input to the ECU. Normally a two pole magnet is used for TPS and the magnet may be of diametrical type, ring type or segment type. The magnet is defined to have a certain magnetic field. In case of failure of the TPS operation the CHECK ENGINE light remains illuminated even if there is no problem or error in the ECU. It cannot be corrected by clearing ECU errors by running diagnostic software. In order to rectify the malfunction the TPS needs to be replaced by a new one.
TPS Throttle position sensor location