Class II Data Line

Saturn utilizes the Class II communications system for most vehicle system controllers that must exchange data and commands. Class II data is pulse width modulated. The pulse width modulation of Class II data allows better utilization of the data line.

The messages carried on Class II data streams are also prioritized. This means if two devices try to communicate on the data line at the same time, only the higher priority message will continue. The device with the lower priority message must wait. The modules on the Class II data line are:
^ Body Control Module (BCM)
^ Electronic Power Steering Unit
^ I/P Cluster
^ Sensing and Diagnostic Module (SDM)
^ OnStar(R) CIM (if equipped).