You don't say what your problem is but a sensor is highly unlikely to be faulty. Garages commonly misdiagnose because of a basic misunderstanding of the engine management system.
How exactly does an engine control unit differentiate between a sensor that is giving a poor reading because of an engine running problem, and a sensor giving a poor reading because the sensor is at fault. The fact is it cannot, and this is why sensors are changed but rarely cure the problem.
