Help before I go mad...

[steve singh]

So my friend dropped off his E46 M3 as he is having major issues with his parking sensors.

In essence when he selects reverse there is a continuous tone which will last for minutes implying his car is right next to some kind of object.

Thinking it was a sensor failure (though they all click) he purchased 4 sensors from ebay - still no success and since then I've put 4 sensors that I'm 100% sure work - still no success.

I then tested the wiring and at each connection adaptor to the 4 sensors I read 11.5v of power and 11v of power in the return feed. I've also done a contunity (sp) test on the return feed between sensor and module and it seems fine.

I have swapped out his PDC control module and no change.

I have checked the feed to the 'gong' and it's fine.

I've connected INPA and there are no PDC fault codes and each sensor is picking up proximity correctly.

I'm at a loss as to what the possible issue can be and it's driving him and me mad!

Does any kind soul know what on earth could be wrong???

Thank you.

[steve singh]

Anyone???

[FreeLitres]

On my old X-Type, if just one sensor was faulty/failing, then the whole system would go into a safe mode as you described (continuous beep when selecting reverse)

Are you sure that those sensors off ebay are all working fine?

[Vvroom]

No idea OP but sounds like you've tried everything.

The sensors on my E46 325 occasionally go nutty in very warm weather. I've driven (forwards) with the rear sensors kicking out a continuous beep for 5 mins on occasion.

[famfarrow]

My dads E46 M3 has just developed this exact problem, I too am interested in what this could be.

[A911DOM]

It doesnt have an aftermarket towbar fitted does it?

Is there not a 'silencing' switch he can use?
I had a towbar fitted to my previous car and it used to sense the bar sticking out so rendered the sensors useless...

Long shot I know...

[chrisispringles]

Are they clean? My dad's E39 has parking sensors and they go haywire if there is any dirt on them.

[E30M3SE]

Just to get this right,
it's had 4 x known working sensor and a known working control unit and still the same issue?

Faulty beeper or wiring from CU to beeper?

Edited by E30M3SE on Saturday 8th September 10:40

[R1 Indy]

Damaged wiring shorting?

[steve singh]

Yep - 4 working sensors and a second hand control module from ebay which did the exact same thing as the original control module.

INPA shows live data from each sensor and they look fine and pick up proximity.

I think there is a wiring short somewhere - the beeper/gong make a noise so I'm assume that's working.