CEL was on, it was a code. Not sure if it would go away or something. The BDC and DME are supposed to sync after some time. Idk. I just register in Montana/Wisconsin to avoid smog.
Yeah. It threw a gnarly code on mine when I put my factory ECU back in at one point. It was some 'drivetrain malfunction. continued driving not possible.' though it drove just fine. I scanned it, and it said something about data mismatch. I swapped ecus back and haven't thought about it since.
Except you cannot clone TO a hardware locked ECU, at least that was my most recent understanding.
Edit: This is not actually the case, and I am a big dumb dumb