Hi.

I recently had ALL of the front-end control arms replaced on my W221 (2012 S550). Shortly after the repairs, while driving, ABS and Traction Control lights came on. Common sense tells me that this is due to something getting messed up during control arms replacements. But I wanted to check and make sure if the ABS sensors/system get touched during the control arms replacements. Any helpful tips or pointer I can give to my mechanic friend for troubleshooting who did this work? Thanks for your help.

Scan the car with a Mercedes specific obd scanner. Could be something like a wheel speed sensor that got knocked around.

Turn the wheels onto full lock and see itf there's anything obvious amiss with the wiring. Should be two wires on one side and one on the other... Extra wire is for the brake pad wear.

They plug in behind the wheel arch lining and this may have been disturbed and chaffed a wire.

Thank you all for tips.

Thanks!!!

Thanks again to a very helpful community for tips and visual guides.

So, an unexpected thing happened today. The light/error message has gone away by itself. Didn't do anything. It was coming up either right when the car was started and it began rolling, or after driving a short distance, or after driving a max of about 10 KM. I only experienced it three times, and those were the only three times car was driven in past week. This evening, I wanted to check the codes using my scanner but the lights weren't there. So, I drove it for a good while in all different styles: slow, fast, rush hour, highway. Drove it turned the engine off drove it again. Etc. But after driving it for almost an hour, the ABS or Traction Control error light + message did not come on. Based on past experience, this was too long a period/distance driven for the light to not have come on. I don't know what happened. May be a lose connection settled in by itself? Don't know what to do now. Am I that lucky? :-)

Be worth just double checking the wires and the plugs just in case. Intermittent faults always have a cause and never fix themselves.

No so lucky after all LOL. Did a scan on the car this morning. There were quite a few fault codes. Cleared them, but the few related to speed sensor don't clear. Meaning the issue is there and persistent. Taking it to mechanic friend this afternoon.
Do these codes point to something more serious?

Thanks.

clearly the car thinks the front left one isn't behaving - did you bother to see if its still plugged in

I would guess that in the process of popping the ball joints out of the wheel carrier the tool slipped and hit/pinched the sensor. Purely speculating.

Worst case replace the sensor. I think they are part# 2219055700 and they are around $200. But look on the wire and there should be a part# stamped on it to get the right one.

All those codes are probably the different systems detecting the fault, all probably related to one issue.

#10 is that sensor.

Car was put on hoist, and all wires and connections were checked on the left side (as reported by the code scanner). No loose connection or pinched/damaged wires were found.
My mechanic friend recomoved the ABS sensor from where it plugs into the wheel bearing assembly. See pic. He said it looks worn and scratchy and recommended that I replace it. He also looked into the socked where ABS sensor goes, and said it is rusty inside too and perhaps I should replace the wheel bearing too because it's speed sensing mechanism is likely worn. (see pic). Plus, its rusty inside and it can damage the new ABS sensor too.

So, my options are:
1. Do nothing. I won't have ABS. The car is rarely driven in winter/snow anyways.
2. Replace ABS sensor, and if that doesn't fix the problem, replace wheel bearing too.
3. Replace both ABS sensor and wheel bearing.

What would you recommend?

Thanks!!!

if the car is rear drive only the front reluctor (the bit that the sensor senses movement of) is the inner wheel bearing seal - they get grubby with disc dust - as its magnetic

sensors fail all quite normal

https://mbworld.org/forums/s-class-w...ml#post8882114

Thanks for the help!
The car is 4Matic.Does that change what I should replace? Sorry don't know what the Body Code is. Can't see it on a site the decodes VIN.

Here are the parts I have located so far on RockAuto:
Speed sensor: More Information for UNITED MOTOR PRODUCTS ABS246

You have the 221.094

I was originally looking at RWD diagrams since thats what I thought you had. 4matic for this job is better in my opinion since you can just press out the old bearing and install a new one, the bearing has the magnets in it. Clean up the hub obviously. For RWD the manual says to always install a new hub and to not just replace the bearings.

I work on my car so if it were me I would clean up the sensor and spray some type of cleaner down in the hole, stick a q-tip in and try to remove any debris in there, maybe blow it out with light compressed air. The bearings are sealed so should cause any damage. See if that works.

If not id replace the sensor. I would personally only use Genuine MB parts or the OE brand. In this case I believe ATE makes the sensors. See if that works.

If not I would replace the bearing. Genuine MB or Timken.

I searched around for the parts just to get an idea on pricing. Its not really that expensive, just the labor.












Instructions on pressing out old bearing and pressing in new bearing.

You (and everyone here) is sooo helpful. A true community feeling I get. I am humbled by the help and support I am always so kindly extended. Thank you!!!!

I was looking around and noticed FCP is selling the NTN front wheel bearing as OE so I searched around for photos of the Genuine MB bearings and the ones im seeing are stamped NTN. Just found that interesting. Seems to be made in Canada.

Found the part #'s on there catalogue page here: https://bcabearings.com/catalog/sear...036&model=1715

yes, very much - the 4x4 ones have the reluctor as part of the sealed wheel bearing see the new 4x4 schematic in post just above
whilst grubby I wouldn’t expect it to be faulty - far more likely the IPC chip at the end of the ABS sensor did the usual trick of expiring - you can't measure these without proper electronic kit

I came across photos of a used W221 4matic wheel carrier where the bearing surface appears worn and looks like you can see the ring of magnets. I also noticed what looks like a notched area at the bottom where maybe its designed to let water evacuate.



Came across the sensor bolt torque spec for anyone interested.

Replace the bearing on both sides of the car for peace of mind.

That's what I am planning to do Thanks.

Also while you're in there, pull the drivers side axle and replace the bearing on that shaft if it hasn't been done. Also change the front differential fluid.

Is that some other bearing that I don't know about? You are talking about the bearing in the right where brake rotors are installed and ABS sensor plugs into, right? Or, is there another set of bearings in the axel area?

Thanks.

when he says axel its called a driveshaft and the bit down the middle to the back is called a prop shaft then everyone in the world knows what they are talkng about

although he may have meant the intermediate shaft that runs through the sump and to replace bearing 140 - but isn't that the right drive shaft that comes out to replace that bearing? or does it pull out to the left side all the way through the sump and really he meant part 200 a bush ?

terrible drawing missing one of the drive shafts off (Parts 10 one on the left and another on the right)