parking sensor ecu

hi all i have a freelander sport 05 plate and im having problems with the parking sensors iv tryed putting it into reverse and checking each sensor for a clicking or pulse but nothing i only get a long beep for about 3 or 4 seconds and the switch flashes then nothing. i took the drivers side rear panel of to check for loose wires but cant see anything out of place im thinking it might be the
the parking vcu which has a part no ecu ywc500142 is there anything else i should check before trying to source another ecu and is it just a matter of changing them over.
thanks tam
anyone know where i can pick one up cheaply

anyone please

The switch flashing signifies there is a system fault but there's no way to tell what it is. The ecu can be interrogated with testbook if i'm not mistaken.

How on earth did we manage to park before these silly bloody things came along, come to think of it I aint got one on my Disco, mmmmmm!! must be driving skill I use to park. :hysterically_laughi