PDC sensors, front fender

[frictioncircle]

About two weeks back I started getting PDC falses when parking.

I'd get "red" distance from the passenger side front fender when in free air. I thought the sensor might have been dirty but when I took a proper look, the sensor had fallen in and was dangling loose behind the fender panel (hence the falses).

I removed the hex-head fasteners in the wheel well and was able to reach up, find the PDC sensor, and push it back into position.

If you've not dealt with these before, the fender sensor assemblies are a black plate of plastic with the round, body-colored sensor sitting in the middle of the plate. Think of an aspirin pill (the sensor) sitting proud of a countertop.

What keeps these PDC sensors fixed in position?

I felt around the area and there doesn't seem to be any obvious attachment points to hold the plate in place. I ended up positioning the assembly so that the sensor sits flush in the fender opening, but just a light push will put the ultrasonic sensor back behind the bodywork.

Anyone have experience with these sensors and how they're properly attached to the body?

 

[spartacus68]

I'm currently fixing a similar issue, but not with the sensor falling out, but with a broken sensor, as in no signal.

Hubauer Shop (Germany) is very good for diagrams. For the front, apparently there's backing plates on the front bumper/fender. Part number: 51117414362. You need last 7 digits of your VIN to search.

Ideally you need to remove the underbody panel, not just the wheel arch liner to get a proper look. Pretty sure these sensors engage with the backing plate, but don't just get pushed into position. On my brother's X5 rear bumper/fender the sensors rotate clockwise and lock into place. I'm sure the BMW i3 is no different.

 

[frictioncircle]

spartacus68 –

Thanks for the suggestion of removing the underbody panel and the details about how the sensors are mounted in the X5.

Once I get mine sorted I'll share findings here.

 

[spartacus68]

Ignore my advice frictioncircle, the i3 PDC sensors are nothing like the X5 in terms of rotate to fit. I had to fit a second hand sensor tonight to clear a parking PDC issue I've had for some time.

Jack up the car, pop off the front wheel, put an axle stand under the subframe chassis just in case.

Remove the 8mm screws and one 10mm nylon hex nut from the wheel liner and remove. Interestingly the wheel liner is in two parts, you only need to remove the section closest to the fender. It's easier out of the way. With full access you can now see the PDC sensors, especially the outer ones, not to be confused with PMA sensors on the wings. For the outer ones there's no need to drop the cover underneath.

The sensor is held in place with a moulded bracket in 4 places. Pressing on the PDC, and unclipping each plastic arm in place you can remove. Clean the aperture with a little WD40 and refit. Check the wiring to the sensor, it's one of these lift clip to disconnect. Pictures here.

https://ibb.co/tJsLsvK
https://ibb.co/F3x9JJs
https://ibb.co/8zDB7Gr

 

[frictioncircle]

spartacus68 –

Very interesting that you found your sensors to be held in by brackets. I have yet to take another pass at sorting my loose front passenger-side (fender) PDC sensor.

In November of 2020 I purchased, for US$10, Munro & Associates' teardown of the i3. It's still available here and is worth the low price to het this level of build detail:

 

[frictioncircle]

https://leandesign.com/tag/bmw-i3/

One thing I found about the PDC sensors is that they're held in by double-sided tape. :shock:

 

[spartacus68]

https://leandesign.com/tag/bmw-i3/

One thing I found about the PDC sensors is that they're held in by double-sided tape. :shock:

I'm sure, but it will be 3M high adhesive tape or similar. Normally during construction - these surfaces will be prepped with rubbing alcohol and the contact adhesive will be very strong.

Did you ever get your one fixed?

 

[frictioncircle]

spartacus68 –

Apologies for the delay in replying to you! From looking at your pictures a second time, it's very easy to see that the mounting plate uses a four-point attachment to hold the PDC sensor.

The problem I had was that the combined sensor & mounting plate assembly fell behind the front fender (technically the front bumper cover).

A few years back I had my front bumper repainted. Seems that my body shop must have pressed the PDC assemblies back into position, not realizing that they required double-sided tape to be re-attached properly.

 

[spartacus68]

Frictioncircle - good to hear from you. I suspect the bodyshop just cut corners on the repair, and instead of detaching at each sensor it got yanked out, possibly by accident. Either that or it was subject to damage?

Is that it fixed now?

 

[frictioncircle]

Yes, spartacus68, it's fixed!

My new 2021 i3s that I picked up at the end of June solved all those PDC issues!