'02 Trailblazer Problems!

‘02 Trailblazer 4.2 L after motor swap, loses Serial 2 data communication with scan tool when ignition is turned to run position. Vehicle no start - no click. Ignition switch has been replaced. DLC tested good. Splice pack SP205 checks good with no loss of communication. Serial 2 voltage jumps very high when key is turned to the run position. All grounds checked and clean. Any ideas?

Almost sounds like something with the passlock system is holding you out. Not sure how that would tie into the engine swap though?!?

Joel