Circuit Description

Each module connected to the class 2 serial data circuit monitors serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the ID number of the module which sent the message for State of Health monitoring. A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. When a module does not associate an ID number with at least one critical parameter within 5.5 seconds of beginning serial data communication, DTC U1000 or U1255 is set.

The table below list the modules on the class 2 serial data circuit that will set a DTC U1000 or U1255 and should be actively communicating the previously described messages on the class 2 serial data circuit.