W204 C250 ABS ABSolute headache!!

[Trtj]

HI all,
I have the full northern lights of ABS, TPMS, ESP on the dash so read the codes.
I am repeatably getting:
C111700 - The signal of component 'L6/2(Right front axle rpm sensor)' is implausible.
C327100 - Implausible values of rpm sensors: speed at front axle.

SO, today i replaced the rpm sensor with a Delphi (OE) part. Code and light still present after a short drive. Swapped back to original, no change, swapped back again, no change.
I then took the hub off to look at the magnetic ring (ABS ring), was a bit greasy and dirty but after a good clean with alcohol it looked fine. Theres no rubbing or clashing with the sensor when put back into place (can the wheel bearing preload affect the air gap maybe?).
All put back together, and still the lights are on and never go off. So I am thinking of many possibilities:
1. The old sensor AND the new sensor is defective.
or,
2. The ABS ring is defective,
or
3. Both 1 and 2.
4. Something going on further up the chain towards the ABS ECU (but there are no codes related to this being thrown)

I am NOT getting a code like - C111000 - Component 'L6/2(Right front axle rpm sensor)' has an electrical fault. So maybe the sensor and wiring is fine?! There seem to be many codes meaning very similar things!

[PositronicRay]

Wiring fault is possible. Try checking continuity, cables in the wheel arch are particularly vulnerable.

[Paddymcc]

Had similar problems on the other halves W246 B class.

Ended up replacing both rear front wheel speed sensors, but not before booking 2 MOTs and the car throwing a hissy fit on the way to the MOTs. Better to replace in pairs after that expensive lesson!

If you have a decent code reader go into the wheel speed sensor sub menu data and you'll find one of them will be reading a ridiculous RPM value compared to the others.

[Trtj]

Cheers both. Tried Delphi and Bremi sensors, and swapped sides. Fault follows the swap, so going to try Merc official ones tomorrow! Here's hoping.

[Paddymcc]

Trtj said:

Cheers both. Tried Delphi and Bremi sensors, and swapped sides. Fault follows the swap, so going to try Merc official ones tomorrow! Here's hoping.

What kind of code scanner have you got? Here's how I figured out what was causing my fault with abs, power steering, esp etc



I bought the cheapest sensors from eBay to solve my issue, £12 a side. I would imagine that you would want each axle using the same brand too in case of any manufacturing differences.


Edited to add just remembered my old W204 C63 had an abs ensor go just after buying it and the AMG warranty replaced the ABS sensor and ring when they recovered it.

Edited by Paddymcc on Monday 1st January 22:11