DTC U1000 & U1255: Class 2 Communication Malfunction: Description

WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.

Modules connected to Class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among modules. When a module receives a message for a critical operating parameter, module records identification number of module which sent message for State of Health monitoring Node Alive messages. A critical operating parameter is one which, when not received, requires that module use a default value for that parameter. When a module does not associate an identification number with at least one critical parameter within 5 seconds of beginning serial data communication, DTC U1000 or DTC U1255 is set. When more than one critical parameter has same module identification number associated with it, DTC will only be reported once. Modules communicating on Class 2 serial data circuit include:

Dash Integration Module (DIM)
Driver Door Module (DDM)
Driver Information Center (DIC)
Electronic Brake Control Module (EBCM)
Instrument Panel Cluster (IPC)
Instrument Panel Integration Module (IPM)
Memory Seat Module (MSM)
Powertrain Control Module (PCM)
Radio
Rear Integration Module (RIM)
Remote Control Door Lock Receiver (RCDLR)
Remote CD Changer
Sensing and Diagnostic Module (SDM)
Theft Deterrent Control Module
Vehicle Communication Interface Module (VCIM)-Generation F1
Vehicle Interface Unit (VIU)-Generation 2.6