Replace rear parking sensor

[MarkH]

I have a replacement sensor arriving from AliExpress next week.
Before I'm ready to tackle this job I want to know exactly how I go about removing the old sensor from the bumper (and fixing the replacement in place).
Has anyone done this and can offer some advice, please?

[MKH]

You will need to take off the bumper fascia to get at the back side. Showed pretty clearly in this video.

https://www.youtube.com/watch?v=tc4jgJuXbIM

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[MarkH]

Thanks Mark.
Yeah, I've already had the bumper off (installing the EcoHitch!) so I know about that.
The other pic I've seen too, but the sensor is not the same as the i3 so the method of removal is not the same.

It may be apparent how to get it out, once I open it up again, but I just want to make sure I don't end up having to reassemble things without having managed to replace the sensor.

[MKH]

Took me a while to find it - not logically listed in the repair guide.

Rear Sensor01.jpg (91.07 KiB) Viewed 11082 times

Rear Sensor02.jpg (82.08 KiB) Viewed 11082 times

[MarkH]

This is the unit that I've ordered. The part number is 66209274427 01, which I think is correct for the i3
https://www.aliexpress.com/item/3270531 ... 5c4eZfQZM6

[MKH]

That is the right sensor according to the part number. Looks like the design may have changed slightly from the picture in the repair guide. Instead of the plug receptacle offset and then straight inline with the sensor head, it now is at 90 degrees - maybe for better clearance.

[MarkH]

Yeah, it arrived today so I'll try to install it some time in the next week.
Let you know how I get on (and if it works - NZ12.85 compared to NZ$295 seems too good to be true. But I figure it's cheap enough to give it a go.)

[MarkH]

I said I'd send an update - and now I don't want to, because it's confusing

I had been enduring this problem (one rear sensor erroneously triggering) consistently for the past 3 months.

Before swapping out the faulty sensor for the new (cheap) one, I did some checking:
- I disconnected the faulty sensor and ignited the car - "Auto PDC failure"
- I reconnect the faulty sensor - it triggers again (with no failure message).
- I swapped sensor 1 and sensor 2 (by position) and the faulty triggering moved accordingly (with the sensor).
- I replace the faulty sensor (in its new position) with the new one - "Auto PDC failure"
- I replace the new sensor with the old faulty sensor (in its new position) - that sensor is now fine but the one that has been moved to the original faulty position is now triggering. (go figure)

In the course of doing all this, I used contact clean on all the joints.

So, at that point, I concluded that :
a) the new cheap sensor doesn't work.
b) the original triggering might have been caused by a wiring problem at that sensor position (but the problem moved when I moved the sensor?).

I decided to bite the bullet and get it fixed professionally.

NEXT day.

When I backed out of the garage - SILENCE!!!
No failure message - everything working as it should

I would like to again test the new cheap sensor (just to be sure it is no good - and I can leave appropriate feedback) but am reluctant to disturb things.

I have discovered that it is possible to replace any of these sensors without having to remove the whole bumper. By undoing 2-3 bolts along the bottom of the shirt, you can get your hand in to unplug the cables. The sensor fits into a plastic seat that has two long flexible posts that run up either side of the barrel of the sensor. To release the sensor, pry these away from the sensor barrel to release the retaining clips. Press the sensor from the outside and it slips out easily.

[WillKeogh]

All of the rear sensors on my i3 were corroded, with paint bubbling, and frequent false alarms when reversing. BMW said this was not covered by the warranty and wanted £600 to fix. Grrrr.
With the car out of warranty I decided to replace these sensors myself, but then with one in my hand it occurred to me to try just sanding off the flaking paint and corrosion and repaint the surface. And it has worked - all 4 sensors now working correctly and no more false alarms. It has been good for several weeks in a wide range of weather.
That ecohitch video was very helpful. It would have taken me a while to find that bolt behind the number plate.

[flyboy320]

All of the rear sensors on my i3 were corroded, with paint bubbling, and frequent false alarms when reversing. BMW said this was not covered by the warranty and wanted £600 to fix. Grrrr.
With the car out of warranty I decided to replace these sensors myself, but then with one in my hand it occurred to me to try just sanding off the flaking paint and corrosion and repaint the surface. And it has worked - all 4 sensors now working correctly and no more false alarms. It has been good for several weeks in a wide range of weather.
That ecohitch video was very helpful. It would have taken me a while to find that bolt behind the number plate.

Just wanted to say thanks for posting this. Two of my rear sensors were acting up and after reading your experience with corrosion on yours, I looked closely at mine and the paint on them was bubbling up. So I removed them (I didn't have to remove the whole bumper, just removed a few bolts on the bottom of the bumper and was able to reach in behind to access the sensor) and sanded off the paint and corrosion (looks like the metal underneath is aluminum?) and spray painted them and they seem good! I did order some non OEM ones (4 for $50 from Amazon) and we'll see if they work as I'm not sure if my rushed spray paint job will hold up over time.