Hi

I'm having some problems with my rear parking sensors.
Car bleeps when engaging revers and sometimes I get another long Error sound. Sometimes I don't.
I've cleaned the sensors and they seem to work intermittently....not picking me up near the rear of the car. When I'm reversing they're telling me I'm about to hit something...when nothing is there.

Is it possible to pop the sensors out of the bumper to check wiring?
Must the rear bumper come off?
Any ideas?

Cheers
Dave