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Discussion Starter #1
Hi guys.
I am co grunting with a situation where a mechanic tells me something, and another one, something else.
The problem is like this.
I have a 3 series e90 with a reader speed sensor not working.
Been to a bmw garage and I have been told that the sensor is faulty and reluctor ring is broken, both need replacing. No bearing needed as its not magnetic.
Now I've been to another mechanic and he said that the reluctor ring looks fine, sensor it's fine but the bearing needs replacing.
Now I don't know what to think anymore.
I have replaced wheel speed sensor twice. No reading coming from it.
Checked reluctor ring, seems in 1 piece. A little bit corroded but no broken or missing bits.
Spoken with a third mechanic and he said that the bearing is not magnetic because it siding the reluctor ring to check speed.
My question is: is e90 using a magnetic bearing and a reluctor ring or because it has the reluctor ring, the magnetic bearing is not needed anymore, and it's just a normal bearing?
Thanks.


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there probably lies your problem,,the reluctor rings corrode and swell,making the gap to the sensor decrease,,there is a way round it by fitting washers /spacers to the sensor to create a gap..sometimes the rings corrode and swell so much that it touches the sensor and wears it down,,so making new sensors wear away quickly..
 

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Just for reference, on the e90 each axel is different;

The 2 front wheels that don't have drive shafts measure speed using a bolt on wheel bearing with a reluctor ring encapsulated into the bearing.

The 2 rear wheels measure speed using a reluctor ring mounted on the rear drive shafts, the wheel bearing is a normal type pressed into the hub.

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The BMW garage you have been to is correct, the reluctor ring has corroded and swollen slightly reducing the air gap between the sensor and ring, giving you no signal. This is a VERY common issue with the rear reluctor ring setup.
 

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Discussion Starter #4
Thank you very much guys.
I will check the sensor to make sure it sends info to abs ecu and if is not, check wiring. If it does, than ECU will be the culprit. Now everything makes more sense and I can do some checks myself.
Just been quoted by BMW stealer £118+vat per hour to diagnose the problem.
Thank you again and I will try to come back and post the findings.




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Discussion Starter #5
Right.
After I got home today I decided to have a look at the abs unit.
Almost impossible to remove abs module connector.
I checked the wheel speed sensor with an obd2 reader and nothing, shows 0 when all other show some measurements.
Replaced sensor twice. No change.
Cannot find a pin out for the plug so I cannot test it at the unit.( If I manage to remove the connector)
I will have a go this weekend testing if I have any voltage at the sensors connector or if the sensor detects wheel movement.
By the look of it, I would say it is a problem with the electoral side of abs if the sensor proves not faulty.
Seen some videos about some Volvo abs modules with broken connections inside. Removing the electronic side of unit will be impossible without removing whole unit which creates another problem. It needs bleeding after putting back together.
Never bled abs unit before, no impa, no OBD2 cable.
My weekend looks promising.
MOT is around the corner which makes everything even worse.

If anyone has any ideas, please share, I could use some fresh ones.


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I would replace the crusty reluctor and sensor at the same time before looking at the module.

Common problem with a simple fix most of the time.

A corroded bulging reluctor ring will destroy a new sensor on the first few rotations.
 

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Discussion Starter #7
Amazing news.
Just decided to check the freaking sensor by swapping it with the driver side. Bloody sensor was faulty. 2 eBay sensors faulty!
Now I just need to buy a new sensor.
So happy it's not the abs ecu!
Thanks for replys guys.

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Discussion Starter #8
I think I'll torch it and throw it over a cliff....
Bought a Pagid abs sensor. Didn't buy a cheap one, I paid £55 for it!
Installed it on car, not working.
Swapped sensors right to left and left to right, left side not working. Swapped them again, left with right, right with left. New sensor still not working!!!!!!!
Used realoem to find the part number, bought it from eurocarparts, good brand. What is the problem?
With an old damaged sensor. It works but with a new one it doesn't?!?!
I'll put some wires in between the wheels and use one sensor for both!!!!!!!
Any ideas before I burst in tears?
 

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3 new sensors not working, but the original from the other side does. sounds like it's the wrong type of sensor.

Is it different sensor types from reluctor rings V's magnetic bearing.? seems like it.

EDIT, had a look at real oem, seems to be the same sensor all the way through the production run - so there goes that idea.
 

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Discussion Starter #13
Last one I bought was from eurocarparts using the part number from realoem. How can that be the wrong one?
I know it looks like it's the wrong part but how can I find which one is the right one if realoem tells me that's the one?
 

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Last one I bought was from eurocarparts using the part number from realoem. How can that be the wrong one?
I know it looks like it's the wrong part but how can I find which one is the right one if realoem tells me that's the one?
i was going to get my sensor from bavarian auto doc,,but they had none in stock,,but the guy gave me a link to e bay for one,,i bought it and its been fine for 3 months,,was £25,,was for my e46 330d 53 plate..
 

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Discussion Starter #15
I think I found the problem.
My car has active steering, sensor I bought it's for non active steering cars.
So stupid of me...
What can I say...I'm a genius...
 

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The sensor seems to different if you have "Usable load increase S100A". Have you checked your equipment according to VIN? Was there any visible difference with the sensor you bought compared to original?
 

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Discussion Starter #17
Yes, I did check my vin.
No increased load, just active steering wheel. I noticed the sensors are different after I checked again the website.
No visual difference from original sensor.
 

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Discussion Starter #18
Fixed it.
There are a few types of sensors.
For increased load, active steering, ,non active steering.
On realoem shows all of them and you need to decide your vin to see exactly what you have and what you don't have.
I have no increased load, active steering.
Bought the right sensor this time. Installed, worked first time.
Didn't pay attention when I bought previous sensors.
Thank you for help guys.
 

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I had the same issue. Area under the Reluctor rings had corroded and forced the rings up towards the sensor wearing out the sensors. Took it to independent bmw specialist and he took off the old rings, cleaned off the corrosion and fitted new rings and sensors and haven’t had an issue in 2 years. Reluctor rings are about £30 a pair
 
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