Circuit Description

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2003 GMC Savana Special, 2003 GMC Savana Camper Special, 2003 GMC Savana, 2003 Chevrolet RV Cutaway, and 2003 Chevrolet Cutaway. However, it is still accessible from the selected car via links, so may be relevant.

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 5 seconds of beginning serial data communication, DTC U1000 or U1255 DTC is set. When more than one critical parameter does not have an identification number associated with it, the DTC will only be reported once. The class 2 serial data line on this vehicle is a star configuration. The following modules communicate on the class 2 serial data line:

The body control module (BCM)
The electronic brake control module (EBCM)
The inflatable restraint sensing and diagnostic module (SDM)
The instrument panel cluster (I PC)
The powertrain control module (PCM)
The radio
The remote control door lock receiver (RCDLR)
The vehicle communication interface module (VCIM)