The throttle cable if you pull it to rev you will see the end of a cylindrical pully that the throttle wire sits around. If you look at the rest point of that it hits a tiny micro switch which is about 2cm Long and 1cm wide it will either have a black rubber dot or a red rubber dot where the throttle activates this switch from rest to load or open & closed postions. There it should be mounted via one or two screws most peeps just push against the rubber cover to hear if it clicks, but if you have a multi meter you cna test the circuit if there is continuity in an open or closed position.
Not sure if you cna just buy the switch I tried many times its sometimes moulded onto the throttle body itself and you have to drill it out just to fit a new one on. In the end I just took one off a whole throttle body!
