Wheel speed sensor covered in muck

[Mymercedes220]

Hi all.
I have abs/traction lights come up on my w204 2011 c class.
Also the runflat inoperable is up at same time.

I have had the driver front wheel off and had a look about I removed the speed / abs sensor and it appears to be covered in muck. Is this normal? I have attached a picture and u140a appears to be a code popping up.
Any thoughts greatly appreciated.

 

[Uncle Benz]

They have a small foam ring that goes around the sensor in its hole to prevent “bits” from going in. Check that it’s still in place. Swarf like that will cloud the sensor and turn what should be a crisp square-wave signal into a less than crisp curve.

 

[Uncle Benz]

It could also be dead though. That’s also common

 

[Mymercedes220]

Yes there is the remains of a foam item! Now just a large hole as the foam has perished.
I guess I can't test the sensor? Just working my way through 50 Google apps to see if I can narrow the issue down with my dongle. I'm just guessing it is the sensor .....
One of these days I'll buy a useful OBD2 scanner

 

[mioba]

I use icarsoft mb v 3. a good scanner will pay for itself immediately.
As you have the sensor out replace it. Get a mb genuine one. They dont like aftermarket speed sensors.

 

[KennyN]

Are these sensors not magnetic , so the buildup on the tip looks like brake dust from the disc + pads wearing down and being "attracted" to the end of the sensor.

Think first year physics with the magnet and iron filings.

K

 

[Mymercedes220]

No , it's filth and grease. Should there be thick grease in the hole ? I'm not sure the make up of what's in there tbh

 

[Mymercedes220]

Also the runflat indicator is showing as inoperative too.
Don't they also work off speed of the wheel?

 

[Uncle Benz]

Also the runflat indicator is showing as inoperative too.
Don't they also work off speed of the wheel?

Yes, they do

 

[Malcolm Johnson]

Was looking back at one of my old posts, June 2020, run flat indicator, speed indicator, abs and traction control. I car soft said the front right sensor was goosed. Bought a Bosch sensor and replaced the dud sensor.
Instantly corrected itself.

 

[Mymercedes220]

Just Thought is say - I bought a new wheel speed sensor from Amazon for £10 and it cleared the fault it's self after fitting and everything is back to normal.
Thanks for advice guys