2002 dt466 code 521 help

2002 international 4300 throws code 521 according to servicemaxx, injector harness is new, suspecting ecm, but not sure if this could be a possible solution. all new clean power connections, swapped ecm relay, i get the 521 code even with injector harness disconnected during an injector test. removed wire looming from injector wires to ecm and see no signs of frayed or bad wires.. wanted to remove wire harness from ecm to do a pin/ohm test, but even after trying to back connectors off with 1/4" ratchet still couldnt pull harness loose from ecm, which is crazy because I've had them off before..

 

It does it even when the injector harness is disconnected at the valve cover. If I disconnect the harness and do an injector(buzz) test code 521 will come back even after clearing all codes, did it 3 times to verify. So the issue cant be an injector. and I get a different description for 521.

521*
INJ
Bank 2 High Side Short to Ground or VBAT

wouldnt that mean the high side(not the common) is shorted somewhere to ground or positive? checked harness and seen no visible shorts. I would assume if it was shorted it would have to be the external harness from ecm to connector of valve cover injector harness