ESP / ABS light comes on intermittently

[Geordie!]

Guys / girls having an issue with my C204 2012. ABS / ESP light has been coming on intermittent. Code comes up front left sensor. Changed sensor, light still comes on. If I clear the code it goes away but returns shortly, if I switch ignition off it also resets light but will come on again still reading left ABS sensor. Swapped front sensors around, still the lights come on and reading left front ABS sensor. Could I have a faulty module ? Surely if ABS module was faulty it would throw a relevant code. Much appreciate some help guys / girls. Thanks in advance

 

[Trickythemerc]

OBD codes can often hide behind each other. I had failed MAF sensor on OBD scan, after some manual/visual poking about it was a £2.00 hose clip split on the intercooler to turbo boost pipe.

 

[Geordie!]

OBD codes can often hide behind each other. I had failed MAF sensor on OBD scan, after some manual/visual poking about it was a £2.00 hose clip split on the intercooler to turbo boost pipe.

Thanks for reply Trickythemerc. Yeah that is common I’ve had boost pressure sensors do the exact same thing all down to a split hose from intercooler to mixing chamber

 

[OneForTheRoad]

Did you buy a genuine mb abs sensor. Aftermarket copies are well known to not work.

 

[Stratman]

It's possible the toothed ring has failed, they sometimes crack and this will cause a fault code.

 

[Petrol Pete]

Are the front tyre of the same age and worn the same , how's the tyre pressure ?

 

[IanW]

The 2014 C204 is probably the same as the W203/W209, in which case the magnet for the front ABS sensor is built in to the rear oil seal on the wheel bearing itself, rather than a toothed ring. I can't imagine how it would fail, but I guess it's a possibliltiy.
In my experience, faulty sensors cause the ABS warning light to come on only after the vehicle has moved a short distance; continuity or circuit failures are detected as soon as the ABS module is powered up and before the vehicle has moved.

Ian.

 

[SpikyMikey]

The 2014 C204 is probably the same as the W203/W209, in which case the magnet for the front ABS sensor is built in to the rear oil seal on the wheel bearing itself, rather than a toothed ring. I can't imagine how it would fail, but I guess it's a possibliltiy.
In my experience, faulty sensors cause the ABS warning light to come on only after the vehicle has moved a short distance; continuity or circuit failures are detected as soon as the ABS module is powered up and before the vehicle has moved.

Ian.

Reluctors can indeed fail: I had one turn up its toes on my S204. As you say it's built into the hub bearing.

 

[Petrol Pete]

Using a fairly cheap scan tool (iCarSoft etc) can show if the signal from the wheel sensor is consistent, better than throwing parts and labour at it.

 

[Geordie!]

Guys thanks for the input. Since the OP I have replaced the left front rear bearing seal that has the magnetic ring build into it, still throws the front ABS sensor, live data has wheel speed reading ok

 

[OneForTheRoad]

Guys thanks for the input. Since the OP I have replaced the left front rear bearing seal that has the magnetic ring build into it, still throws the front ABS sensor, live data has wheel speed reading ok

Did you use genuine mb ring/seal ??

 

[Geordie!]

Did you use genuine mb ring/seal ??

yes

 

[OneForTheRoad]

yes

Mb sensor ??

 

[Geordie!]

Mb sensor ??

Absolutely. I have used after market sensors before with no issue. When I swapped with the right hand sensor it still come up issue with the left front ABS sensor. Would I have a code if it was the module N30/4

 

[markjay]

Have you considered the possibility of damage to the wiring (not the bit that comes with the sensor)?

 

[Geordie!]

Have you considered the possibility of damage to the wiring (not the bit that comes with the sensor)?

Possibly, when I return from offshore next week I will have a look at the wiring, clean the connectors etc.

 

[Geordie!]

Using a fairly cheap scan tool (iCarSoft etc) can show if the signal from the wheel sensor is consistent, better than throwing parts and labour at it.

Hi Petrol Pete, I have the MB icarsoft V2, great tool. Live data has all four sensors reading the same

 

[RichardF]

I had this, looked okay but sensor wire copper core deteriorated. Wiggle test confirmed it, new piece spliced in and joined inside the inner wing.

 

[geoffus]

I’m a little confused, if it has the live data of sensors all the same, how can it show the front left sensor has a fault?
Are you monitoring the sensors whilst driving the car above 30 mph ?

 

[Geordie!]

I’m confused too, hence why I’m asking on here. This is not a black and white typical sensor fault. There is something else going on but your right if it was a faulty sensor I would see it on the live data