Class 2 Data Line Circuit Description

Saturn utilizes class 2 communications system for most vehicle system controllers that must exchange data and commands. Class 2 data is pulse width modulated. The pulse width modulation of class 2 data allows better utilization of the data line.

The messages carried on class 2 data streams are also prioritized. This means if 2 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 2 data line are:

• Body control module (BCM)
• Power steering control module (PSCM)
• Instrument panel cluster (IPC)
• Inflatable restraint sensing and diagnostic module (SDM)
• Vehicle communication interface module (VCIM), if equipped