W221 Rear speed sensor/reluctor ring issue

RoyRogers

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W221 2007 320cdi. W639 2011 Viano 2.2
I've just had the usual ABS/ESP warning light & diagnostics said to check the rear right speed sensor.
After checking and replacing the sensor the fault remained so I purchased a new reluctor ring but before changing it I put it on my lathe and tested the new sensor with my multimeter and all seemed to be working +/- 40mv ac. After replacing the reluctor ring on the car I did the same test on the car and got no reading, took the car for a run (being hopeful) but ABS/ESP lit up again on the dash.
I'm not sure what i'm missing here and wondered if anyone else has had this issue.
Thanks in advance
 

Botus

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on this model its recommended you change both sensors as a pair - they ALL die to time circa 9 years old

on mine the error message would not clear until I set a destination in the sat nav then it was all back to normal within 200 yards
 
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RoyRogers

RoyRogers

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W221 2007 320cdi. W639 2011 Viano 2.2
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on this model its recommended you change both sensors as a pair - they ALL die to time circa 9 years old

on mine the error message would not clear until I set a destination in the sat nav then it was all back to normal within 200 yards
Thanks Botus
I'll give that a try. I've never had to replace both sides at the same time although probably a good idea.
 

Botus

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yes only one fails but the Merc document on repair, specifies always replacing both at the same time.
 
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RoyRogers

RoyRogers

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W221 2007 320cdi. W639 2011 Viano 2.2
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UPDATE
I purchased another sensor and after fitting, my diagnostics showed that I now had a fault on the left side. As I never had a problem before, I realised that the issue was with the sensors. I have now purchased 2 new sensors direct from Mercedes and all is working as it should. One new issue I had when both sensors were showing as faulty is that my steering went very heavy.
 

Botus

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thanks for the update....
 


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