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?

 

[Anonymous]

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

 

[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.

 

[Anonymous]

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

 

[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/32705316405.html?spm=a2g0s.12269583.0.0.29725c4eZfQZM6

 

[Anonymous]

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.

 

[jfs1969]

Thanks all above for posting very helpful. I'll add my experience in case of use to anyone, it was easier than I thought it would be ;-).
Girlfriend complained of intermittent false signals from parking sensors on her 2017 i3. I had a look and two of the 4 rear sensors were corroded, paint intact but bubbling.
Thought I might as well replace all of them as probably the other two would go one day. BMW Brighton quoted £580 to replace all 4 sensors. £300 parts plus £180 labour.
I had a look on ebay and you can get aftermarket ones for £10 each and ones from Valeo, who are the OEM supplier, were £25 each. I was pretty confident these would be fine but slightly worried about doing the job myself as I'm a somewhat reluctant mechanic. I once changed a rear sensor on an Audi A1 and the back panel didn't go back on very tidily, leaving uneven panel gaps. But I saw the video above and, crucially, the comments that you don't need to take the whole panel off so gave it a go.

• Tools - 8mm spanner - that's all you need!
• Undo the ~5 self tappers along the bottom of the rear panel. Also remove the plastic bash plate it screws into to give yourself a bit easier access, another 4 or 5 self tappers.
• With one hand behind panel gently pushing the tabs on the sensor apart, and the other hand gently pushing the sensor from the front, they pop out easily.
• Disconnect from cable.
• Remove the rubber seal from old sensor and fit it to the new one.
• Push the connector on. It only goes on one way or at least will only click in one way.
• Press back into its hole making sure seal is not pinched and the sensor is flush.
• Repeat for the others.
• Get into car and check they are working.
• Refit the bash plate and screws for the rear panel.

It took me one hour in my slow and steady way. I can't believe it would take a competent mechanic more than half an hour. I don't know BMW Brighton's hourly rate but they are probably charging 2 hours for this job which is a piss take.

 

[coachark]

1.) How did you all pinpoint which sensor was faulty? I am getting a failure message but no indication as to which of the four is inoperative.

2.) Does anyone have a link to a sensor that they know works? I’ve only been able to find them for $150+.

Thank you.

 

[flyboy320]

1.) How did you all pinpoint which sensor was faulty? I am getting a failure message but no indication as to which of the four is inoperative.

2.) Does anyone have a link to a sensor that they know works? I’ve only been able to find them for $150+.

Thank you.

I had ones that went bad due to paint deterioration on the face of the sensor so it was easy to tell which ones were giving the error. I ordered cheap Amazon ones and they worked great;

https://www.amazon.ca/gp/product/B07SWJKTKG/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

 

[coachark]

1.) How did you all pinpoint which sensor was faulty? I am getting a failure message but no indication as to which of the four is inoperative.

2.) Does anyone have a link to a sensor that they know works? I’ve only been able to find them for $150+.

Thank you.

I had ones that went bad due to paint deterioration on the face of the sensor so it was easy to tell which ones were giving the error. I ordered cheap Amazon ones and they worked great;

https://www.amazon.ca/gp/product/B07SWJKTKG/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

Thank you for the link. My paint is all intact so unfortunately I’ll have to come up with another way to troubleshoot. At $15 per unit I would just order four sensors but unfortunately they only have one left in stock.

 

[bazza2000]

Just wanted to post a thankyou for the procedure. I picked up a replacement sensor (original corroded) for £22 and then followed the procedure earlier in the thread. Its as simple as removing a few screws and popping in the replacement. I didn't even need to jack the car up, there was enough clearance for me to get my head under the bumper and flex it enough to replace the sensor. Just saved me £280 the local BMW specialist wanted to charge me. Took me about 20 mins. Thanks again.