I have a 2000 sd with a v10.it stopped runnig Has fuel pressure but no injector pulse or spark.A guy told me to check power at the relay behind the radio.It had no power when cranking.I ran a kill switch to it and the truck started right up and ran great for a day and then nothing. Here are some of the things I have changed, maff,tps,iac fuel press.reg,cam sensor,crank sensor all plugs and cops.I dont know where to go from here i hope someone can help

 

Ran a kill switch to the relay? What is "it"?

 

What codes is it showing? Both the cops and injector pulse width are controlled by the ecu.