P38 Cutting Out

I have a 1995 P38 DSE that when you are driving along the car seems to lose all power, you lift off the throttle and go back down on the throttle and it comes back to life. The other problem is the engine cuts out and the diagnostic light comes on, then you have to restart the engine again on the key, can anyone help? Many thanks

not very clued up on deisel but i would suspect a fuel problem, has it had new filters at any point recently?