hello all.

had a recent problem with the epc light coming on. i had a scan done at audi and they reported back that a nox sensor and control unit needs replacing. i have been quoted a total of £658.75 to have this done and it seems really expensive to me. as of now the light doesn't come on, is it doing the car any harm by not having it replaced? and if it definitely needs replacing, is it the kind of job i can get done cheaper elsewhere? thanks for your time.