DTC U1255 - Serial Data Line Class 2 Initialization Error: Notes
WARNING: This page is about a different car, the 1997 Cadillac Seville, 1997 Cadillac Eldorado, and 1997 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
WARNING:
To avoid air bag deployment and injury when trouble shooting system, only use test equipment specified in diagnostic tables. Under no circumstances should battery powered test equipment or test light be used. Carefully follow all instructions.