Hello. I have a 2008 Volvo s40 2.0 D4 and Iately I've been having a problem with it. It accelerates to 100mph/160kph normally but then after 100mph it cuts off throttle response and decreases speed while displaying an Engine System Service required. I recently serviced the car less than a week ago. It only displays the engine system service required after going past 100mph/160kph. Anyone with an idea of what could be the problem?

 

Not many diesel experts here (we didn't get that version in the colonies, sadly). Offhand it could be a fuel pressure / flow problem, but no matter what it is, checking for OBD codes is your best way forward. Too many possibilities to start guessing and throwing parts at the problem.

 

Engine system service req. wont throw a CEL. You would have to scan with VIDA to see what is tripping the message.

 

seems like you have enough HP to get up to 100 mph so I'd look at things like intake air or exhaust restrictions, fuel pressure / flow. Could be something in the injectors or injector pump as well.