ABS issue, codes for both front wheel speed

[familycarguy]

Hi everyone,

I've just bought a facelift C180 estate on a 13 plate for bit of a bargain price. I'll get some pics up, hoping to do a few tasteful upgrades, reversing camera, headlight upgrade etc.

Reason it was cheap is ABS and traction lights are on.

I scanned the car before buying it and it had a code for Front Left wheel speed implausible data.

I've got the car home now, and after bit of driving around, it became undriveable, it was locking up the rear brakes under any acceleration.
Now when I scan it, it has codes for both front wheel speeds.

I unplugged one of the sensors, cleared the codes, and then car drove fine, but obviously still had lots of codes.

I then swapped both front sensors from left to right and vice versa. The sensors are genuine MB and appear to be in good clean condition, with no damage to the wiring or connector.

If I clear the codes and start the car, all the warning lights remain off, until I drive the car. As soon as I drive it, I get codes for both front wheel speeds and the car puts the rear brakes on.
If I clear the codes, start the car, and disable ESP using the car's menu, the warning lights come on, but the car drives just fine.

When observing the wheel speed values using a scan tool, the two fronts are showing 0.

Is there anything else I should do, or would you agree that it has damaged/contaminated ABS rings, and I should probably just order 2x wheel bearing kits which comes with the ABS ring. Or am I completely wrong and something more serious could be at fault? Any thoughts welcome. I'd rather diagnose it properly rather than fire the parts cannon, since it all appears to be nice and original.

Attached are the codes, cheers,,

 

[ToeKnee]

Have you tried replacing the front wheel sensors? I've just replaced one on mine and externally it looked fine and undamaged but once replaced everything is back to normal.

 

[familycarguy]

Have you tried replacing the front wheel sensors? I've just replaced one on mine and externally it looked fine and undamaged but once replaced everything is back to normal.

No I haven't, it seems a bit strange to have both sensors fail at the same time, but I suppose I could replace them anyway.

 

[Bellow]

If I clear the codes and start the car, all the warning lights remain off, until I drive the car. As soon as I drive it, I get codes for both front wheel speeds

That is pretty much a symptom of failed reluctor rings or, some other cause for the wheels to be read at wrong speed (eg, wheel/tyre diameter discrepancy). Lights at key-on without motion point to circuit or component failure, waiting for the wheels to turn points to implausible data.

 

[markjay]

I'd replace both front wheel sensors simply because they do fail, and even if this isn't the current issue, then you'll have two new front sensors good for another 30k miles.

Once you've eliminated the wheel sensors, you'll need to look further up the chain, including ABS module and ESP ECU.

 

[familycarguy]

That is pretty much a symptom of failed reluctor rings or, some other cause for the wheels to be read at wrong speed (eg, wheel/tyre diameter discrepancy). Lights at key-on without motion point to circuit or component failure, waiting for the wheels to turn points to implausible data.

That makes sense, I've got some new sensors to fit now, and if they don't fix it, I will go for the wheel bearing kit next. There is also a minor buckle in one of the wheels, but I don't think its enough to cause an issue, the wheel and tyre sizes are all correct as far as I can tell. Its got a matching pair of tyres on each axle with even wear.

I'd replace both front wheel sensors simply because they do fail, and even if this isn't the current issue, then you'll have two new front sensors good for another 30k miles.

Once you've eliminated the wheel sensors, you'll need to look further up the chain, including ABS module and ESP ECU.

Only 30k? I mean I've bought aftermarket ones so I wouldn't be surprised!

 

[markjay]

That makes sense, I've got some new sensors to fit now, and if they don't fix it, I will go for the wheel bearing kit next. There is also a minor buckle in one of the wheels, but I don't think its enough to cause an issue, the wheel and tyre sizes are all correct as far as I can tell. Its got a matching pair of tyres on each axle with even wear.


Only 30k? I mean I've bought aftermarket ones so I wouldn't be surprised!

Sadly, yes, the genuine MB sensors (made by ATE) often fail at 30-40k miles. Though some do last longer....

 

[familycarguy]

Success! Fitted two new aftermarket ABS sensors on the drive and the car is fixed! £20 fix!!
I'm just thankful I don't have to pull the hubs off to replace the rings !

 

[ToeKnee]

Success! Fitted two new aftermarket ABS sensors on the drive and the car is fixed! £20 fix!!
I'm just thankful I don't have to pull the hubs off to replace the rings !

You're welcome.......

 

[familycarguy]

Have you tried replacing the front wheel sensors? I've just replaced one on mine and externally it looked fine and undamaged but once replaced everything is back to normal.

This was the fix, thank you for the suggestion! Still not sure how it managed to have two failed at the same time but that's how I got it so