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W221 Rear speed sensor/reluctor ring issue

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by RoyRogers, Jul 31, 2020.

  1. RoyRogers

    RoyRogers New Member

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    Joined:
    May 29, 2007
    Location:
    Plymouth, devon
    Your Mercedes:
    W221 2007 320cdi
    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
     
  2. Botus

    Botus Senior Member

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    Joined:
    Jul 29, 2014
    Location:
    UK
    Your Mercedes:
    S500/2010/500
    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
     
    bembo449 and malcolm210 like this.
  3. OP
    RoyRogers

    RoyRogers New Member

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    Joined:
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    Location:
    Plymouth, devon
    Your Mercedes:
    W221 2007 320cdi
    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.
     
  4. Botus

    Botus Senior Member

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    Your Mercedes:
    S500/2010/500
    yes only one fails but the Merc document on repair, specifies always replacing both at the same time.
     
    bembo449 likes this.
  5. OP
    RoyRogers

    RoyRogers New Member

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    Joined:
    May 29, 2007
    Location:
    Plymouth, devon
    Your Mercedes:
    W221 2007 320cdi
    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.
     
    bembo449 likes this.
  6. Botus

    Botus Senior Member

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    Joined:
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    Location:
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    Your Mercedes:
    S500/2010/500

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