DTC U1255: Class 2 Initialization Error: Description
WARNING: This page is about a different car, the 1998 Cadillac Eldorado and 1998 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
When vehicle is started, PZM requests information from other modules on class 2 serial data line. DTC U1255 will set when PZM requests information from a particular module, and that module is not "on-line". PZM will then use default values. DTC U1255 will clear when module providing the requested information comes back "on-line".