I replaced my EBCM with one from an 02 Grand Prix, the car wouldn't start unless I held it in run for a couple seconds. Once started the lights brake/Trac/abs light would stay on but there were no ABS codes. There was codes for U0100 and U0300. I put the old EBCM and it starts fine now.

I don't see any 5's in the replacement EBCM, what could be wrong?