isx12 cm2250 fuel pressure only builds if injector harness is disconnected

[num1enloe]

ok ill hook up to it. it holds psi but only with injector harness disconnected. if disconnect at the head crank it over it builds up to where it could fire off but it cant cause the harness disconnected and if i key off quick reconnect harness it fires off but dies instantly as pressure drops. i actually just got done checking over the entire engine harness for shorts and high resistance. everything checks good. im thinking ive got a calibration issue. the crazy thing is this truck was driving dow the road and died and has not fired off since. no sign of pump issues prior or even fuel issues.