Throttle position sensor l series diesel

having a probllem with my throttle position sensor
ive fitted a second hand one but problem still there with over reving
if i had cleared the fault code first then fitted part would that solve problem as i now have a third sensor!!! 3rd time lucky..land rover want £520!!...any help please...i have no air leaks either
thank you
Eddie

still not much luck with a second hand unit...now i notice the hill decent light comes on so i think it could be a electrical problem to ecu
thing is doing my head in
Eddie