E87 Rear Parking Sensors not working

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mjleat
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E87 Rear Parking Sensors not working

Post by mjleat » Mon Nov 26, 2018 9:26 pm

The rear parking sensors on my E87 are not working. The front sensors are working fine. I've checked the PDC unit and there doesn't seem to be any signs of water damage. There's the tiniest bit of corrosion on one of the pins but the PCB is immaculate.

There is no noise at all when you put it into reverse and no warning lights. I can’t hear any clicking from the sensors but it may just be too loud where I live for me to hear it.

What do you think is the most likely cause? Thanks

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Re: E87 Rear Parking Sensors not working

Post by marco_polo » Mon Nov 26, 2018 9:27 pm

Is your reversing light coming on?
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Re: E87 Rear Parking Sensors not working

Post by mjleat » Mon Nov 26, 2018 9:29 pm

Hi, thanks for replying.

Yes the reverse light works.

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Re: E87 Rear Parking Sensors not working

Post by marco_polo » Mon Nov 26, 2018 9:31 pm

New symptom, or has it always been like this?

Do the beeps usually come through the rear speakers, or through a separate 'sounder'?

Changed your stereo or done any electrics recently?
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Re: E87 Rear Parking Sensors not working

Post by mjleat » Mon Nov 26, 2018 9:36 pm

I only bought the car last week and I missed that they weren’t working when I bought it. Stereo and everything looks original and there’s no invoices to suggest any work has been done recently besides a new clutch.

I’m not sure where the sound comes from. I thought it might be the head unit but was then confused that the front parking sensors are working and wondered whether that ruled out the head unit?

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Re: E87 Rear Parking Sensors not working

Post by marco_polo » Mon Nov 26, 2018 9:44 pm

What age is it?
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Re: E87 Rear Parking Sensors not working

Post by mjleat » Mon Nov 26, 2018 9:50 pm

March 2007, facelift

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Re: E87 Rear Parking Sensors not working

Post by marco_polo » Mon Nov 26, 2018 9:53 pm

That's a very early FL!

Should come through the speakers at that age, I think. Are the rear speakers working correctly?
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Re: E87 Rear Parking Sensors not working

Post by mjleat » Mon Nov 26, 2018 10:15 pm

Yes it is!

I’ve just been out and checked. All speakers are working. It’s a professional head unit and there’s no option to adjust bongs in the menu.

I’ve listened again for clicking on the sensors and can’t hear anything, but I don’t think it will ever be quiet enough where I live to be able to hear them.

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Re: E87 Rear Parking Sensors not working

Post by marco_polo » Mon Nov 26, 2018 10:57 pm

Does the headunit have chrome rings on the two knobs?
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Re: E87 Rear Parking Sensors not working

Post by mjleat » Mon Nov 26, 2018 11:22 pm

4EA45B8B-996F-4EE3-A749-297D4E7E1D35.jpeg
4EA45B8B-996F-4EE3-A749-297D4E7E1D35.jpeg (112.96 KiB) Viewed 596 times
C1D8BE93-FD06-414F-B6C2-0E995CEFDA9D.jpeg
C1D8BE93-FD06-414F-B6C2-0E995CEFDA9D.jpeg (96.36 KiB) Viewed 596 times
Yes it does have the chrome rings.

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Re: E87 Rear Parking Sensors not working

Post by marco_polo » Tue Nov 27, 2018 8:30 am

Ok, so that suggests it's the correct HU for the FL car, and that the bongs should come through the rear speakers.

Fronts work so it's not a power/fuse issue.

The reverse sensor on the gearbox works correctly, so that brings us back to the PDC system itself.

I'd go somewhere quiet, put the ignition on (starter button once without touching the pedals), select reverse, and do some more investigations for us. Broken wires, corrosion, witnesses of water ingress/crash damage, etc.
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Re: E87 Rear Parking Sensors not working

Post by mjleat » Tue Jul 16, 2019 11:45 am

I fixed this problem in the end. I took off the rear bumper and check all the wiring and sensor connections, which were all fine.

I tested the PDC module using ISTA and it said it was functioning fine.

The PDC sounds come through separate front and rear bong speakers in this age of car and I tested them using ISTA and both were fine.

When using ISTA to read the individual sensors, all fronts worked fine, but all of the rears just read 255cm regardless of what you put next to them.

I tried changing the PDC module for a used one and the functionality was exactly the same, so changed back to my PDC module.

I finally changed all of the rear sensors for second hand genuine BMW Bosch ones from eBay. I changed them one by one thinking that it may just be one or two that were faulty and the others may work when those ones were replaced, but in the end, I had to replace them all. The sensors were £15 each on eBay so it wasn't an expensive fix after all.

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