After an accident impacting the rear-bumper, the reverse-sensors don't function anymore, shifting into reverse usually (not always) makes a solid-beep for about 5sec then stops, sometimes it does not make any noise.

What does that sound-pattern indicate? There is no relevance if there is something near the bumper or not (they make no sound after the initial long-beep)

The 3 of 4 sensors appeared to survive the incident perfectly. The 4th popped out of the socket (into the bumper) but was otherwise fine. It appears that the auto-body guys painted over the sensors, could that be causing this? It is possible they did not plug them all in securely (will crawl under and check after I recover from an injury), what happens if one sensor is not plugged in, do they all stop working?

 

The sensors should work if only one has gone bad. Being painted over will definitely stop them from working.
Try cleaning the paint off, then put the shifter in reverse with the ignition on. With your ear close to each sensor you should hear a slight clicking noise. No noise would be either a bad or disconnected sensor.
The sensor wiring runs from the bumper to a module in the trunk/boot beneath the lining.

 

The LOOONG beep indicates an ERROR that something is wrong with the system.

bob

 

Bob, would it throw a code? What could be potentially wrong (in my scenario) that would generate that beep?

 

The system is independent of anything else on the car. It's the sensors and the control box in the trunk.

You need to get down and put your ear on the sensor -- with the car in reverse. You should hear each sensor "clicking" ... don't kill yourself. Those not clicking are dead.

The actual sensor slips into the holder (bumper color) that goes into the bumper. They should have removed them ??? The sensors are a Ford part .. very cheap on e-bay $!5-$20.

 

All fixed! The clicky trick worked! THANK YOU! One was not connected.

Fyi, if one is disconnected none work. Also, painting them does not do any harm, they work fine now painted.

 

Yeah, anyone else doing this - leave the engine OFF with key in On position PLUS e-brake PULLED FULLY UP

 

TOO much paint can affect the sensors!! We used to get cars back from the body shop with non functional reverse parking aid. All sensors connected and 'clicking' but still faulty.

Removed the sensors and wiped paint off with solvent, system functioned normally.

Sent car back to body shop with request to LIGHTY paint the sensors (OK).

bob

 

Okay, I'm wrong paint does indeed mess up the sensors - it does not stop them from working, but their measurements are fairly erratic now and occasionally miss something small like a persons leg!

What kind of solvent or other method will remove car paint + clearcoat? If I just scratch it off with a razor blade, would I potentially mess up the sensor?