My 2005 S60 is randomly losing power while driving and sometimes the engine cuts off completely. The fuel pump duty cycle is around 0.14% when in fact it should be 30% or thereabouts at idle and fuel pressure is steady at 400 kPa.
Driving around hooked up to VIDA and getting constant readings on the fuel pump and fuel pressure it is obvious that the duty cycle is doing something screwy. Sometimes it goes way above 0.14% while other times it goes down to near 0.
From what i've read on the web, this could be an issue related to the fuel pump or the fuel pump control module. How can i determine which one is causing the problem without having to replace both parts?

Thank you for your help.