I have had this Emissions control light coming on and off for the last year, when i had my car serviced last September they said they would reset the switch, and see what happens. I may need a new one which would cost about £250 if it came on again, is this correct. it only came on last Mon then didnt come on for 3 days, now it is permantly on again. Do you think it could just be a loose wire. When the light is on, the engine does smell is it to do with this?

Jackie