Rear Parking Sensor Problem: "Check Rear Park Aid"

[kabiblueline]

Our 2011 Limited began intermittently showing a "Check Rear Park Aid" on the left side screen (next to the speedo.)
When this happens, the reverse camera still works, but you get no warning beeps for object detection.

I had written it off as likely due to winter dirt accumulating on the sensor.
However, now the warning is constant, and I've checked and cleaned all of the sensors.

Older Fords used ultrasonic sensors for rear object detection. These were fairly easy to diagnose and fairly cheap to replace.
Our Explorers apparently do not use this type, as they seem much more expensive (~$100 per sensor online)

Does anyone have any thoughts on how to diagnose which sensor might be failing?
How easy is it to access these sensors from behind the bumper?

Would a code reader be kind enough to tell me which of the 4 has failed?

Thanks for the advice.
[I tried searching the archives here, but I only found 1 related thread with no answers. Thought I'd start a new thread with clear title as easy reference for others when this happens.]

 

[peterk9]

The reason you are not getting warning beeps etc is because of the "Check Rear Park Aid" alert. The camera operates independently of the sensors. I don't know if this issue produces a code or not. Perhaps some other member would know.
A negative battery cable disconnect sometimes will clear some issues like this but I can't say whether or not it will in your case. It will however result is things being set back to factory default and loss of saved memory functions.
Hopefully another member can be of more help. It would also be helpful if you added the trim level (Limited) to your profile so it shows in the margin when you post. It has been added as requested info upon registering. Thanks.

Peter

 

[Macnerd]

On my 2016 XLT the Front Park Sensors were behaving similarly, but very intermittently, and the dealership pulled the front bumper. They told me that the wiring harness of one of the sensors was pinched causing an intermittent short and shutting the system down and they replaced it within a few hours of getting the part in. I hope this information is helpful to you, unfortunately I have no experience actually diagnosing it or replacing myself.

 

[kabiblueline]

Finally got this issue fixed.

I poked around up under the rear bumper, but none of those sensors are easy for the layman (or at least me) to access.

I did finally take it to and independent shop. They were able to diagnose a loose/slightly broken connector on one of the sensors.
They were able to get it back together and fix it so it should not come loose again.
Charged me $60.