So I turned the ky on, engine off, trans in reverse, waited for all the pumps and other things to quit making noise, and sure enough, I hear clicking (faint clicking) out of three out of the four sensors. Problem solved!!!! almost... I called the local stealership to see what one would be worth... $198!!!! EACH!!!! Are you F'n kidding me???? its a little pos hunk of crap I can get for $20 from a wreckers? Ya kno its cheaper to pick up a complete bumper with sensors off a parted out truck on kijiji?!?!?! Anyway, I know the solution and now I just have to find the way I will go about doing it. Thanks for the response, as speedy as it was as well as accurate!