S15/T15 Sonoma P/U 2WD V6-4.3L VIN X (1998)
Information Bus: Reading and Clearing Diagnostic Trouble Codes
DTC U1000 Class 2 Communication Malfunction
CIRCUIT DESCRIPTION
Modules connected to the class 2 serial data circuit monitor for 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 identification 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 identification
number with at least one critical parameter within about 5 seconds of beginning serial data communication, DTC U1000 is set. When more than
one critical parameter does not have an identification number associated with it, the DTC will only be reported once.