W221 2012 60k miles - Speed Sensor / Ring

[mbmb123]

Oh joy, the car that keeps on giving.

Swapped over my 20 inch wheels for the 18 inch set (These aren't new to the car, they do fit)
Half a mile down the road and the ABS / stability control / tyre deflation warning light tells me those functions are inactive.
My first thought was that maybe when fitting the 18 inch wheels that had previously been on the car, and after 8k I'd swapped front to rear, maybe when I'd refitted I'd put a original front on the left front but a rear on the right front.
Not that there was much difference in wear, just a little extra wear on the edge of the tyre for the fronts. But maybe the system was super sensitive and detected a difference in circumference between the fronts that freaked it out.
Nah.

Hooking up the code reader I see
- L6/2(right front speed sensor) check installation of sensor and rotor
- L6/2(right front speed sensor) carry out visual inspection
- unreasonable values from rpm sensors: front axle
- L6/2(right front speed sensor) Test wiring / plug connection

And using the code readers other function , while driving it showed the correct speed from 3 sensors and virtually nothing from the front right.

Removed wheel and inspected wiring, looks good. Disconnected the main plug that goes through the wheel arch and reconnected.
Removed the speed sensor and used boroscope to take a few snaps and the "ring"
Trouble is, I don't know what a good one looks like, there appears to be damage.

Thoughts?

 

[mbmb123]

Unplugged from the wheel arch end and checked resistance. According to Mr google it should be around 1k ohms. It was open circuit.
So I've rang MB to get a price, they're getting back to me.
The cheapest on the internet is a £13 Ridex, £65 for a Bosch..waiting for the MB price, I'm expecting >£100.
I'll never buy MB again
....yep £123 from MB Dealer.

 

[mbmb123]

Got the new speed sensor. That's open circuit too.

 

[mbmb123]

But if the Speed Sensor is an "active" type, you can't measure resistance to determine a bad sensor.

Wheel Speed Sensor Diagnostics for Meters and Scopes

There is no way to quickly tell if a Wheel Speed Sensor (WSS) is passive or active. Both sensors have two wires and are located in the same position on the vehicle. Often, the service information will not indicate what types of sensors are on the vehicle. Trouble codes will not indicate if the...

www.tirereview.com

.

Looks like I just wasted my money

 

[steveq]

I had a speed sensor fail on my 2011 C220.
I replaced it with a genuine MB one and all is good again.

The sensors fail - nothing physically wrong with them. It is common issue across all makes.

 

[mbmb123]

But is it the speed sensor or the reluctor ring?
After consulting Mr Google I thought it was the sensor as it was open circuit. But digging deeper there are passive and active sensors.
The active type, which I may have, do present as open circuit, so you can't use that to determine failure.

 

[mbmb123]

Fitted the new speed sensor...it's fixed the problem..

 

[AMV]

Fitted the new speed sensor...it's fixed the problem..

Good to hear, i had to fit one a few months ago, it was stuck in there good and proper!