A couple more questions:
1: What sort of modification did you make to the Ps2?
2: When you say "black screen," do you mean that the Ps2 outputs a full black frame, or that it outputs no audio/video signal at all?
If this happened after installing a mod-chip it could be due to incorrect wiring, beyond that though I am not really sure, there are many potential variables. It seems odd that a faulty motor driver IC would keep the whole thing from booting properly. Maybe this causes it to fail some security check?