Hey brother, I hate to say It but we have never actually locked a 01-05 Duramax since we have been in business. I'm more than happy to help, however, unlocking is not going to help as we never lock the ecu on 01-05 dmaxes. I have a few suggestions for the shop to try, but ultimately it is very likely something causing a communication issue. To datalog it (which is what I assume he is trying to do) even if the ecu was locked it is still possible to log. The only time he would need to unlock the ecu (if it was locked) would be if he was trying to flash it and have it returned to stock settings.
Let me know if I can help further.
Kory:happy2: