Car wont crank unless obd2 cable from accessport is hooked up!!! 2015 STI

So in a bit of a nutshell at the moment.Havent hooked up my accessport ever since i rebuilt my block but i left the obd2 cable hooked up the obd2 port ever since. Deciding that i wasnt going to get the car protuned and leave it stock i decided to unplug it to sell with the accessport but when i unhook the obd2 cable the car doesnt crank over and the C DIFF light flashes in the guage and no fuel pump sound but when i connect it back in it turns on and you can hear the fuel pump. Any ideas?