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Marty, ASE Certified Technician
Category: Mercedes
Satisfied Customers: 54838
Experience:  Bosch Certified Master Technician with over 35 years experience in the automotive industry.
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Martyr, I have a 2002 slk r170 230k (post face-lift) with 6

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Hi Martyr, I have a 2002 slk r170 230k (post face-lift) with 6 speed manual transmission .
About 6 months ago, I started having an intermittent bas/esp light coming on, with associated lack of cruise control, or abs or esp function, as to be expected. Often it was only on for a few minutes and would go off again of its own accord.
About 3 months ago I had the car re-mapped and the guy informed me that intermittent nsf speed sensor failure code was stored in the tpu... Which would explain the issue, probably. However....
Yesterday my speedometer failed intermittently also and again today.
I understand that the abs/esp controller takes readings from the wheel sensors to allow it to do its thing. What concerns me is that the issue has progressed over time...
My question is this: If the speedo has stopped function, does this mean that ALL 4 speed sensors have failed? Would this be more indicative of a faulty control unit than the sensors?
I have also read that it could actually not be any of those but actually the rotation contact located just behind the wheel.
(Ps I know that it sounds like I have been irresponsible to not get it fixed before, however I am not affluent and was stung by MB when they charged me 1200 quid to *not* fix my non operating roof last year, so I read up and looked at it myself, very easily identifying a broken cable in the rear folding pillar, which I then fixed myself for 76 pence for a length of wire! I don't have another 1200 pounds (or more) for them to not fix this!)
Customer: replied 1 year ago.
rotation contact just behind the wheel = just behind the steering wheel, possibly called the clock spring??

Hi, the speedometer fault is due to a faulty front wheel speed sensor. You should get the car connected to a Mercedes tester to read out the fault codes in the ABS/ESP control module. There should be fault codes for one or both front wheel speed sensors. The left front sensor is typically what Mercedes uses for the speedometer signal. This could also be a faulty ABS/ESP control module but a faulty front wheel speed sensor is more likely to be the cause.

Let me know if you need anything else.

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