Hi, great thread. I'm having the same ABS sensor issue as you after doing the R56 Alloy Rear Trailing Arm mod. I'm using Bosch R56 OEM ABS sensors and my left rear works perfectly but my right rear gives me all sorts of issues. Writing this in case it helps anyone:
- at key on and vehicle stationary my speedo cycles/reads something like 5,10,15,18 kph - using a scan tool FL,FR,RL = 0 kph but RR causes the speedo error i.e some sort of fault causing a read of 5,10,15,18 kph.
- when I drive FL,FR,RL all read correctly and sometimes RR reads correctly but at some point a series of incorrect readings (seen on drag tool) triggers ABS/DSC off/warning.
- I've tried three Bosch sensors each one has the same error symptoms - false read stationary and mostly incorrect readings when driving. I think it's sensor gap.
- I tried filing down the plastic mounting face/base of the sensor - initially this fixed the ABS for a day, but the next morning the issue returned.
---> Next I'm going to try filing down a sensor further (decrease the gap more); then put in a spacer washer (increase the gap); then try the R53 sensors; and then if no success I'll buy either an OEM or OEM Value line bearing in case the magnetic ring is the issue.
Does this seem sensible?
I wonder if a non-OEM bearing and non-OEM sensors were your issue, perhaps your mechanic put in a Genuine Mini rear wheel bearing? Would love to know. Really annoying (I think gap) related issue.

 

Hey there! I had replaced my LR wheel bearing with a Timken unit some time before I did the R56 trailing arms and that seemed to be the culprit. However, during my own diagnoses, I had swapped the rear wheel bearings and the problem did not follow the Timken bearing, so I was very confused when replacing the Timken with an OEM unit solved the issue. Perhaps it is as you say, some faulty interaction with the sensors and the bearing, but I genuinely couldn't tell you.

Funnily enough, that OEM bearing in the LR is already making noise again.

 

Thanks for the info - Interesting. I've got OEM R53 wheel bearings and OEM R56 sensors both sides. I wonder if the R56 wheel bearings work better with the R56 sensors meaning I should fit the R53 sensors. I'll try it and post the results.

 

Wish I could be of more help - can't really remember what I did, though I do think there are mounting issues with trying to reuse the R53 sensors on the R56 arms. Another shop ended up fixing the problem with the OEM bearing and I don't recall what sensors the car ended up with.

 

@Laup99 Could the problem be with the connector or the wiring from the connector to the module?

 

I fitted an R53 sensor on the RHS Rear without careful positioning and it fixed the issues straight away! I think the R53 sensor should be used with the R53 wheel bearing and R56 sensor with R56 wheel bearing - they're matched pairs. Also I'm guessing you should use the sensor/bearing that's matched to your ABS module, so again, the Siemens R53 sensor/wheel bearing. I think if you're careful the R56 sensor and R53 bearing can work as with my LHS Rear, but I'm going to swap out the R56 (Bosch) on the LHS for an R53 (Siemens) part - I'm expecting it will work straight away but I'll post here. If it works it'll be 2/2 for the R53 Siemens OEM and 1/4 for the R56 Bosch OEM sensors.

 

In case it helps anyone: R53 sensors are definitely the way to go with R56 alloy radius arms!

Even though the R56 sensors fit the arms, I could only get 1/4 to work using Bosch OEM sensors. I tried increasing and decreasing the gap with the R56 sensors but couldn't always get a good reliable signal, and I also got misreads - signal when stationary with some spacings. The R53 sensors may be slightly too small for the hole in the alloy arm but they work in any position. I'm guessing the R53 sensor, wheel bearing magnetic ring and abs unit signals are all matched and the R56 is slightly different - close enough to work in some situations but different enough to cause issues in some cases.