Intermittent E46 rear parking sensor fault

[Fun Bus]

Now, have done the usual searches first but still wanting to ask the PH masses.

I've a 2004, E46 coupe and the rear parking sensors have started playing up. Sometimes, they work fine, other times I engage reverse and it's a constant tone. I know jet washes can affect them and this first happened after a trip to a hand car wash (been using them for ages but worry someone got over excited on Saturday) so am concerned water has got into one of them. So, anyone else had this? Is it a case of a new sensor or do they 'dry-out' (naive maybe).

As always, thanks in advance.

[Romanymagic]

Had the very same problem once. Checked the little disc sensor things in the rear bumper and one had worked loose, repositioned and the problem went away.

[westmoorfarm]

Mine flat lines (as I call it) every now and again, usually relates to water in some way. Resolves itself after a day or so...

[LordGrover]

Mine does this. I've noticed one of the sensors has blisters/bubbles in the paint. Maybe I'll try bursting them and see what happens...

[Craigwww]

Yea mine is the same, one of the PDC sensors intermittently works when it can be bothered. Been meaning to replace it for ages but can't justify the cost for a sensor.

[d7jab]

Got this problem too.
Put key in ignition, turn to position 2 (before the point of starting) put car in reverse and got and put your ear next the parking sensors. They make a clicking sound...it is very quiet but you can hear it...check all sensors, the ones not clicking either need replacing or you can take them out, clean them up and WD40 them to make them work again.