Sometimes while driving, the ABS light decides to come on/off. Sometimes it won't come on at all, sometimes it stays on for a while and sometimes it just goes off while driving. This was diagnosed to be a left rear speed sensor, but even after getting that changed, no difference, so I decided to get the ABS ring changed, however, still no difference. The ABS light just seems to come on and go off whenever it feels like it, as well as "ESP Defective" and "Service Brake! Visit Workshop!". Any idea what it could be? Been hooked up to many diagnostic machines, and they still say left rear speed sensor as current while the ABS light is on. All the wiring has been checked too and it all seems to be fine.
ABS sensor w211
- Thread starter ayvo
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David404
Active Member
You say "many diagnostic machines" were these generic or the official MB Star diagnostic machine?
If not Star seek out an Indie with a Star machine.
If not Star seek out an Indie with a Star machine.
it was diagnosed with star as well.. said left rear speed sensor
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Drive it with a real time diagnostic connected and see what it reports for each wheel speed.
D
Deleted member 149005
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I understand abs / wheel speed sensors need to be changed in pairs, on the same axle as the brain doesnt always correctly know which side is faulty...despite the error code suggesting otherwise...
yeah we tried that, when the ABS light is on it does not receive a speed from the left rear sensor, even though the sensor and ring have been changed..
so do you think I should try changing the right rear speed sensor?
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So does this mean it is coming and going (ABS error)?
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I have had a number of speed sensors changed on various cars, never needed to do both wheels! Once had the error show up 40 miles after a new rear sensor, it was a new fault but on the front rather than the back
yeah, its basically the same as how i described it in the very first message. its intermittent.
but even after changing the sensor, the abs light still came back on after driving about half a mile and said the same sensor when diagnosed..
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Then I would assume the sensor or associated fitting or connection is likely to be faulty,not another wheel !
sensor is fine, been replaced, and all the wiring has been checked and all the wiring is also fine including connections etc
D
Deleted member 149005
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As posted, possibly a (second) defective sensor - you might not have replaced the faulty one...
so do you think even though it says the left rear isn't showing speed it may be another one not showing speed and its mixed them up? do you think I should jack the car up and spin each wheel individually to see which one is which and which one doesn't show speed?
grober
MB Master
If the rear sensors are the same you could try swapping rear sensors side to side? If the intermittent fault moves then its the sensor. If it doesn't then its local to the hub/brake in question. I wonder if there's any excessive end float/wear on the rear hub bearing causing lateral movement? Does the fault sometimes occur on cornering rather than travelling in a straight line?
Agree with Grober's thinking, if the fault is intermittent then one possible cause is variation in the gap between the reluctance ring and the sensor head. The gap is critical to detecting rotation so any float can change the gap, also check the seating of the sensor it must be fully home in it's mounting, any crud that stops it sitting fully home will increase the gap and could make intermittent miss reads more likely.
