GM's Class 2 Communications System
Yes, Class 2 wiring is a relatively new thing in the
automotive electronics world. In the good old days, you had
a couple of power wires, a couple of ground wires, and some
speaker wires. No big deal. Starting with the 2000 model
year, GM has encorporated Class 2 wiring into the J-body
platform.
The Class 2 system is a Serial Data Link used by GM in its
vehicles, and is based on the SAE J1850 protocol, which is
widely used in the U.S. It is through this data link that
the body control module (or BCM) receives information and
commands that are essential in determining its mode of
operation.The BCM is connected, through Class 2 wiring, to
the instrument panel cluster (IPC), the powertrain control
module (PCM), the data link connector (DLC) and the radio
(RADIO -ha ha!).
For more information, visit this site: Introduction to In-Vehicle
Networking