thanks for putting up with me dont have much faith in our only dealer last guy drove in with similar fault stayed for a week got charged an enormous amount of money just to drive out in limp mode.
I think my next test is to remove engine pipe and check atomization of adblue (could this cause problems is it unheard of i assume it should be a fine mist) even though pressures are ok.
Just for some more info fault seems to be brought on just after truck has climbed a big hill or done some 100km/h freeway driving