Evan31

I have a 03 chevy 1500 4x4 that had a 4.3 in it then i picked up a lq9 out of an 03 escalade but everything is was going good till i got to wire my starter up then when i put the key to acc it will start cranking. I am using the escalade harness, and ecu but im using the trucks fuse box. but when i switch the fuse box to the escalade fuse box on the bottom side there are 3 plugs and all the wires are red and they dont fit into the escalade fuse box and when i use the escalade fuse box i get nothing but when using the trucks i get relay sounds and one dash light which is engine light. can someone help me out?

jetech

Starting schematic for 2003 gm trucks Thanks to Brendan for the info