where is the cut off swich located in the citroen c5 or the fuel pump?

Got the same Problem on a 51 plate C5 HPI, starts and then after 1 or 2 sec's it cuts out. Suspect it's the ECU? Have had it tested by a local chap using diagnostic equipment but seems to through up random error codes which are unrelated. Looking to buy a new or second hand ECU? Can get it run in limp mode by taking off the sensor on the injection rail?
Anyone got any advice apart from scrap the thing?

Carl
March 2009