ecu to fuel injector harness?

your injector is gone. The ECU is an all system work or none type of deal, since to understand why you need to lay out how the whole fuel management system works. I am not going to go into detail but there are at least 3 parameters that must be met on each injector in the ECU every single firing if any of them is not working you would get an instantaneous yellow light on your dash and system will prevent you from actually driving away, will start sort off but wont hold because it would shut off before the damaged fault is read. When the system still allows the other injectors to work than is because the fault is external to the ECU, and most likely a sensor but in your case sounds like the injector it self.