My Cruze randomly started getting terrible mileage and threw a P0004. It doesn't appear to be a very common code at all since I haven't been able to find any fixes aside from changing the fuel pressure sensor in the fuel line back by the tank. (which I did, don't know if its fixed yet) The fuel pressure is controlled by the chassis control module located in the trunk as there isn't an external regulator. That could be an issue. I also read that in general, this code is usually caused by a alternator overcharging, but I don't know how valid that is.

Has anyone else experienced this? 2011 Eco Manual

Edit: Code P0004 is "Fuel Volume Control Regulator Circuit High". Should have put that in first.