Joined: Tue Sep 15, 2015 6:38 pm. x 4985. Re: C4 ad blue/emissions fault/service light. by GiveMeABreak » Fri Mar 17, 2023 2:58 pm. Possibly. You would have to show it was the same issue and that it has continued to be so. Youi haven't provided much info on the vehicle (mileage, age, exact C4 model), in fact it would be better to pop your VIN Dgu7pIO.