ASR/ABS lights

The ASR and ABS lights on a C200 estate stay on after ignition. Cruise control no longer works. I am told this is likely to be one of the ABS detectors/Speed detectors on one of the four wheels. I would be
grateful for anyone's thoughts on this diagnosis.
If it is the case how can I ascertain which wheel's detector has failed? Finally are the detectors difficult to fit?
Thank you.
--
Robert

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first off check your charging circuit mate I had very similar symptoms, turned out to be bad battery, and alternator losing it - causes the system to turn off abs etc when the Voltage drops too low, even if it starts first time etc.. If it is the sensors they are just one bolt, but you need to check their resistance before replacing any, they aren't cheap - cleaning them out (and the toothed ring on the wheel ) may help hth cheers
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How about when you shutdown and restart right away?
I suspect it is the battery too.
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If the light[s] do not go out after starting, you have a power supply problem.
If the light[s] go out after starting but come on after the car moves, you have a wheel speed sensor problem.
The system does not know a sensor is bad when you first start the car. The car has to move and the sensors have to send back a A/C ~ voltage signal. No voltage = light comes on.
In your case, do NOT throw money away on sensors.
You have a voltage supply problem.

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