Anyone know what a auto throttle sensor is on a 94 land rover discovery?

My Land rover (94) discovery is dying when I back up and I was told it is most likely the auto throttle sensor. cant seem to find the part when i do a part search. Can anyone help?|||it is a throttle position sensor. the effects of a failing sensor would not be reserves to one gear. reverse takes a great deal of power for a few reasons. if your fuel economy and power output from the vehicle have suffered, it could just be time for a tune up. ill send you a link for the part that you are looking for though.