2008 reverse sensors

[DJT]

Yo chaps!
My nice new 2008 XC90 has parking sensors front and back.
They worked fine until a few days ago when selecting reverse, the sensors just make a constant beep tone and wont stop until the car is out of reverse gear. Front ones work fine.
Tried turning them off for a while but to no avail. Wiped the sensors, didn't think that'd work, and it didn't.

Anyone got any ideas?

Ta

[SwissXC90]

Has it rained recently? Mine stop working sometimes after rain, where the rear of the car has become very wet.

Try to extract any moisture out from the tiny gap between sensor and bumper. User tissue paper to draw out the moisture.

If that resolves it, water wicking in the gap is the problem, as this causes the ultrasonic pulses to be reflected back by the bumper itself.
I saw a service bulletin about this once... the permanent solution is some form of sealant or gel to stop water getting in the gap. I've never tried it.

Otherwise, a single sensor may be faulty. VIDA will tell you which one.
People with sensitive fingers say they can feel or hear the sensor pulsing, but I've never had luck with that. I must be too tough.

[Familyman 90]

I suffered with this intermittently. I waited until we had some prolonged warm weather to dry it all out and used a syringe to put some silicone sealant down the gaps around the edges.