Copy and paste this link, " Ford Ultrasonic Backup/Parking Sensors 4F23-15K859-AA ", then go to ebay, paste the link in the search box and you'll see these sensors for $7.99 a piece. Buy all 4 and replace them all. They're improved from the original sensors and a lot cheaper ! I was quoted a price of $120.00 for 1 sensor from a dealership at an hour and a half labor to replace. Bill would have been well over $250.00 to replace the 1 bad sensor from them. I purchased 4, replaced them all and it works great. Just spend about $32.00 (plus shipping) for 4 and problem solved. I know there's a post here on how to remove the bumper just dont have it on hand. It's pretty easy, lift tailgate, remove left and right tail lights, just below removed tail lights, remove the hex screw that's angled with a socket on each side, then remove a screw on each side underneath bumper near tires, then along top of bumper underneath rubber seal, remove all the locking pins, remove bumper and place on a blanket or tarp, disconnect wire harness from passenger side of bumper, flip bumper so you see the styrofoam, remove 3 large steel nuts from the plastic bolts that hold styrofoam in place with a deep 1/2" socket, ease styrofoam out gently, replace all sensors, connect harness and gently lay it back on tarp with sensors facing down ( you may have to prop harness side up a bit so harness has some slack, now go start engine and shift to reverse while keeping foot on brake and you should hear the tone sounding from the reverse sensing system. If so, shut off engine, reassemble bumper in reverse order and then you're done ! It took me 1 hour and 15 minutes to do it so its not time consuming.
