Abstract: A throttle position sensor having a potentiometer module which fits into a connector casing for mounting on a carburetor or and air-fuel mixture control system for an internal combustion engine. The position sensor assembly is mounted such that movement of the butterfly valve and thus the throttle, acts to move the wiper element of the potentiometer in a predictable manner. The modules can be tested independently of the casing and rejected without unnecessary waste. Additionally, the same potentiometer module can be used with different connector casings. The potentiometer module includes a one piece casing having an integrally formed cantilever bearing system with two spaced bearing surfaces for rotatably mounting the rotor holding the potentiometer wipers and a "pilot diameter" boss aligned with the axis of rotation of the rotor. Longitudinal movement of the rotor within the casing is limited by position two stop members on either side of an annular ridge extending outwardly from the rotor.