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Hello, back again with issues with my 2011 350 4matic.
I was having interment issues with what I assume is my factory wheel speed sensor. It would work sometimes and the it would give me an error on my cluster. I decided I would replace it with a wheel speed sensor from fcp euro
I purchased https://www.fcpeuro.com/products/mercedes-abs-sensor-ate-2045400517
Now it says it works with my GLK but when I popped it in it worked for a moment and then the car started acting worse than before, bucking around and having trouble turning with the ABS light one 100%. I was even to the point to where the car would not move until I gave it more gas and it released. I attached my scan tool and it said that the wheel speed sensor was not recognized by the CAN bus.
I followed the old part and even cleaned out the hole it sits into. Plug in everything how it was originally and ran through all the mounts.
I'm going to contact FCP and see if it is just a faulty part or if it actually does not work.
I found out that the wheel bearing on the front contains a magnet that trips the wheel speed sensor, which could be the failing part instead of the sensor itself. I ordered the correct bearing from FPC and disassembled the passenger front steering knuckle. Once out I removed the hub and then took out the snap ring that held the bearing into place. I used a shop press to push the old bearing out and cleaned out the area so that area would be free of any rust or scale. Once the new bearing was pushed into place I replaced the snap ring and put everything back together. After clearing the codes everything looked good until i started moving and the ABS and traction control lights came on again. I had to switch it into dyno mode just so I could move around and drive it on a daily basis. I am still showing the issue and I ran my scan tool to check the signal from the wheel speed sensors. All of the wheels register the current speed correctly except for that passenger front wheel which won't register at all until I hit 15 M.P.H. and that wheel registers 189 M.P.H. I am not quite sure what exactly is going on and if I missed a step or if I need the magnetic ring in the bearing and the wheel speed sensor to be a specific gap apart. I can't seem to find any information on alldata pertaining to this. If anyone knows what I may have missed it would be greatly appreciated to be told or shown what I did incorrectly.
I have never heard of using a magnet for a wheel speed sensor. As stated above, there is a thing called a "tone ring" which is a big disk with regular slots cut in the outer edge creating "teeth" that pass the sensor. The sensor senses the frequency at which the cuts pass the face of the sensor and the ABS controller converts frequency into wheel RPM. It looks like this:
The only thing you can do is make sure the slots and the faces of the high spots are clean. The distance between the ring and the sensor is important. If the sensor is lifted away from the ring even a little it will give false readings.
I don't know if your part is compatible, and you didn't say what sensor you were dealing with, but I got these part numbers for a 2011 GLK350 4matic. I don't know if all 2011s were the same, though, or whether yours is 4matic. Neither matches the number you have.
Front A 204 905 31 05 (Looks like this may be superceded to A 204 905 42 05)
Rear A 204 540 13 17
I checked some more sources and it's very confusing. I think you should look it up for your specific VIN.
OP, curious what made you think it was speed sensor issue and not ABS/EPS module or wiring somewhere?
Yea there is a magnetic ring that part of the bearing and read by the sensor. I don't think those really go bad. Wheel speed senors are also pretty simple to just go bad on a street car. I have cars that are much older than GLK with original bearings and speed sensors, it's very basic technology.
Is it magnetic, or just inductive? As I said, I've never seen a system that uses a magnet. A magnet would quickly become fouled with iron particles.
What I have seen in my 2006 cayman is a bearing seal/cap that is magnetic (it will stick to metal). How it's actually made is beyond my knowledge. The bearing sits inside of the knuckle and won't get any debrie on that ring/seal. Knuckle itself has an openning for the wheel sensor tube to be in close proximity to the bearing. It's the same old design but incorporated into the bearing instead of a separate wheel. I assume GLK might have something similar.
I have seen tone wheels incorporated into bearings, but they are not magnetized. Magnets and bearings generally don't mix well. The magnet is in the sensor and the tone wheel distorts the magnetic field around the sensor which induces a current in the sensor coil.
There was conflicting information between the different sources of the diameter od of the bearing.
If you look it up by VIN in the EPC it will return the part used on that particular car. Only if you somehow changed the wheel bearing to one with a different OD would it be "wrong."
If you look it up by VIN in the EPC it will return the part used on that particular car. Only if you somehow changed the wheel bearing to one with a different OD would it be "wrong."
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