Hi, i've just brought a ford mondeo tdci 130 ps, and I have a few issues and wondering if anyone could shed some light on them, when idling the car runs quite rough at times but other times it will be fine (typically it was fine on the test drive) basically as I said it idles rough, also at high revs the glowplug light comes on and it goes into limp mode (doesnt cut out) I had the fault codes read and it come back with p0251.

I was wondering what this is likely to be, I notice I still have the old type (black) cam sensor and I was wondering if the cam sensor would cause this code or not and what else it could be.

Any help would be much appricated.

Luke