First time post so hopefully I did this right. I’ve been battling both rear wheel speed sensors to read correct speed. Speed sensors were replaced with new ones, INPA will read them correctly until it hits a certain rotation and both go out and come back on quickly. 3 typical lights come on dash and go out whenever they decide to. Codes are both p1774/p1775. Can’t narrow down the issue. Steering angle sensor works as it should. Front wheel speed sensors also rear correctly. Debating if it’s both reluctor rings but would be surprised they are both out at the exact same time. If anyone has any idea on possible issues let me know! I’ve gone through multiple forums trying to find an answer and just can’t get it to work. Thanks!

Hi, which type of rear speed sensors did you buy? I had issues with lower cost sensors in the past…. Did the old sensor show any wearing due to the abs rings? Is the tachometer working properly or does it also show issues (signal for the tachometer comes from rear left sensor)….
The rings can be the issue, you could check them visual and do somes tests if proper distance is equal, if the old sensors did not show any scratches the ring may be OK… you could also add for testing some distance (washer) under the rear sensor and check the signals again….

Changing the Abs rings is a bigger job, but doable…

Hope this helps, let me know what you find out.
Cheers
Ralph

Not sure what the codes mean, what is the description?

Another question, the old sensors had the same failures?

Ralph11 wrote

Hi, which type of rear speed sensors did you buy? I had issues with lower cost sensors in the past…. Did the old sensor show any wearing due to the abs rings? Is the tachometer working properly or does it also show issues (signal for the tachometer comes from rear left sensor)….
The rings can be the issue, you could check them visual and do somes tests if proper distance is equal, if the old sensors did not show any scratches the ring may be OK… you could also add for testing some distance (washer) under the rear sensor and check the signals again….

Changing the Abs rings is a bigger job, but doable…

Hope this helps, let me know what you find out.
Cheers
Ralph

Thanks Ralph! I’ve been dealing with this for a bit. Old sensors were worn a little so I know they hit. Replaced with Bremi sensors from FCP. Old sensors were replaced because they were giving the same codes. Cleaned out the rings again today, added a washer to space it. I know the sensors work as INPA does give readings, however I notice they are very sporadic. The front are consistent with speed while the rears bounce in speed. I think I just need to hone in on the exact distance to work properly. I really don’t feel like changing the rings because I’ve read so many forums about how horrible it was. It’ll be a final option. I’ve got no issue with tachometer, that works as it should. Thanks again Ralph! I’ve replaced the transfer case gear also incase you were thinking about that as well.

Hi, it sounds like the rings are very likely the problem. Yes it is quiet a job to do, but doable at home.
So you had no changes with your shimming test? By the way, this not always works as a quick fix if the rings are too far off, mine looked even good but the rust is below and bents them like an oval.
What you could do:
Check all sensors if they all show reverse when you drive backwards and forward when you drive forward (Had issues with low cost sensors which always showed reverse, causing the 3 lights), but then you should get different codes like 5dec and 5e5c.
Get a scanner which shows graphical higher resolution signal of speed, not just speed value, if there are fluctuations -> rings
Add an Oszillation meter instead above and check the signals directly for fluctuations
Measure the distances mount / top of sensor holder to ring complete 360

I am not familiar with the codes you listed, so I am not sure about your scanner… you may get another scanner test for further details….

Good luck!

But since you already see fluctuations on your rear sensors speed signals, rings are very likely your problem, some scanners should give you more detailed codes for this

Attempted a few more trials this weekend. Added washers drove the car. Removed washers drove the car. And got similar results in fluctuating speeds. I’m sure the regulator rings are warped and need to be replaced. I’ve got some new codes this weekend as well. I’ll attempt to attach them here although not sure if I’ll do it correctly. Not sure if it’ll be worth it to just replace the entire axle with the already installed regulator rings or just replace rings. I got this car on a trade from a VW so I’m not trying to spend tons of money on a car with over 220,000 miles. Just trying to get it road ready but still safe at the same time. I’m almost tempted to just drive the car as is. It brakes great and doesn’t give many issues while driving. 👍🏼

Strange that you got also front speed sensor failures, did you reset all failures after you did various tests and then test drive again to see final failures? If you don’t fix it you will have issues with 4 wheel drive and more critical with the abs, assuming you have the known three lights on. You can disable the vtg with the fuse, but the lights / missing functions will stay…. I would replace the rings only, because fairly cheap but you will have to remove all rust, if the rings are too loose you will have to glue them tight, remember the correct location…. ( sensor needs to be in centre of the ring) If you observe that the joints are already worn out (play) you better exchange the whole drive shaft… the rear left side is more difficult due to exhaust and stabilisators, not much space, but doable. i bought the little stabilisators and flexed the old one out (too much rust, could not open properly) …. Cheers Ralph

Okay. So this weekend I was able to put in new axles. I said screw just replacing the rings as it almost seemed more difficult than replacing the entire axle. Yes it was a pain but manageable, I honestly thought it would be worse when reading through posts and videos. They were original from 2007 with 225,000miles. Seems to almost fix the issue. I have to dive back into the codes and see if it sorted the issue. I took one small test drive and seemed stable for the time being. I may have the replace the sensors again as the new ones I installed with original axles got scraped and torn up. FCPEuro for the win with lifetime replacements! Thanks again for the help Ralph! I’ll keep it updated once I remove every code! I’ve come a long long way since I owned this bmw 🙂

Congratulations, well done! Should be OK now, lets see….. Did you observe a play in the old axles? I had a little play in the left rear axle, but re used it anyway…. Cheers Ralph

I can’t quite remember how much play they had unfortunately. I do know the rubber boots started to tear and the regulator ring was no where near a nice circle anymore. Still going through some testing this coming up weekend to finally clear any other issues and check over the car once again to get it road ready. I’ve come to far with this car to not get it back on the road these days and I am excited.

The only way to proper check these rings is to remove the drive shafts, the rust is below the rings, mostly even below the coating and it makes an oval which causes the input/sensor issues…. I tried to measure with the drive shafts installed, but it did not really work. I dont know why bmw did not implement the same design as the front, which is no problem unless the bearing has a problem, from my pov much better solution….. but on the other hand my rings failed after 200000 Km, which is not bad at all…. So far no other issues with my car, only the rear shock rings failed 3x times, window opener, left mirror and the cooler fan. Very reliable car with fairly good diesel consumption….. I like it 👍… Fingers crossed that yours works now and hopefully you will get same experience….