Powertrain Control Module Diagnostic System Check (3.4L): Notes
WARNING: This page is about a different car, the 2002 Pontiac Grand Am and 2002 Oldsmobile Alero. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
The presence of DTCs which begin with "U" indicate some other module on Class 2 serial data line is not communicating.