It’s probably the steering wheel angle sensor which has failed, these cannot be bought separately, only as a whole steering wheel. The problem needs a diagnostic machine to verify, if this is the case a new steering wheel is the answer. The car looks to the steering wheel angle sensor to see how much steering input you have when deciding how to brake safely in an emergency. Safety note: the ABS and ESP may not work properly in an emergency if these are faulty.
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Smart Car Specialist
Unit 10
Foundation Units
Westfield Road
Slyfield
Guildford
Surrey
GU1 1SF