Asoulutely nothing!!
I bought the car 2 years ago and everybody I spoke to said the DOHC engines were trouble. I can safely say I have had nothing go wrong with the car at all. The electrics have not given me any trouble either. I can get 44mpg and the car will do 130mph, not a bad combination I think.
I had a Ghia 2.0i auto hatch which was one of the last with the "old" 2.0 single cam engine. A cracking car in every way with very few problems, it carried me as far afield as Norway in total comfort during the 3 years I had it (from 9-12 years old) ; just remember it's a Ford so you need to see proof that it's never missed an oil change before you buy one!
I originally posted this review a few years ago. I've had loads of cars since Rover 400, Granada scorpio, Scorpio ultima, Omega elite, Citroen xsara VTS, Renault laguna, Escort Si and NONE have even come close to the reliability of my old sierra. Why do they not make cars reliable anymore!
Too many electrical gadgets to wrong now I think. If I had the money I would buy a brand new mondeo and not have to worry, but unfortunately I haven't.