The in-tank pump (this was renewed?) is only needed when tank is below ~1/3 (transfers fuel from other side of the saddle tank. Inline fuel pump (Nr.1 in diagram) is what you can clearly hear when you turn on ignition. There is no sensoring for supply pressure on these with M57N engine so the only code it could give is for low rail pressure when there is not enough supply feed for HP fuel pump. DDE activates fuel pump relay feeding both electric pumps when you turn on ignition to pos. 2 and keeps it activated as long as engine is running.
https://www.realoem.com/bmw/enUS/sho...diagId=16_0567