My '11 F250 has had the typical backup alarm issues were they always scream when put in reverse, so I got another new set off ebay a few months ago and replaced all of them. well this seemed to work for a few weeks and then I started getting a notice on the screen saying "check back up assist" or something like that, it would pop up maybe once or twice in a week. now its on all the time and I don't even know where to start. I check the plug at the rear that goes all the sensors and its good. is this something the dealer has to scan to check or can I do I on my own?

 

Are you in an area that is seeing snow or frost? Sometimes a small accumulation of either can cause them to go off.

 

I am, but even with clean sensors they don't even work now, system is disabled and says "check back up assist" every time I start the truck. I have to hit to OK button in order to get the message to go away every time the tuck is started.

 

Yep dirt too. Anything in the hitch receiver like a bike or luggage carrier will cause it to sound continuously even though it's below the sensors.

 

there is no dirt, nothing in the receiver... the system does not even work now, no alarm.. nothing, just displays a message every time I start the truck basically saying the system does not work

 

If you have a stethoscope or a sensitive ear you should be able to hear them clicking when in reverse (at least this worked on my GM, assuming Ford uses ultrasonic too). If no sound from one then it's dead.

 

If you put your original ones back in, any difference? Were the ebay ones you bought Ford part's, or knockoff?