Throttle Position Sensor Replaces: Mercruiser 803148 / Volvo 3855296 Fits: MCM / MIE 350 Mag, Blk Scorpion Ski (0L005900 & up) 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.