So, I found some interesting info in the 2001 body diagnostic procedure manual under the verification tests section.
Bullet point 4
"If PCM has been changed and correct VIN and mileage have NOT been programmed, a DTC will be set in the ABS and Airbag modules. In addition if the vehicle is equipped with a SKIM, secret key data must be updated to enable start.
For abs/airbag, enter the correct vin and mileage in PCM and erase codes in abs and airbag modules.
For skim, connect DRBIII and place SKIM in secured access mode by using the appropriate pin code for this vehicle."
meh..... this sounds like a shit sandwich...