your year or for a different year? Just because the main harness attachment fits into the ECM there may be different pin lications for the injector wires. Check the continuity from each injector harness to each correct ECM pin.
You note that there is 12v at each injector connector and that should confirm the power portion of the circuit. Is your replacement harness design one that is not 12v to the injectors unless the ignition is on? Was your original harness the same design?