DeVille V8-4.6L VIN Y (1998)
Data Link Connector: Description and Operation
Class II Serial Data
Description
U.S. Federal regulations require that all automobile manufacturers establish a common communications system. General Motors utilizes the Class II
communications system.
Operation
Each bit of information can have one of two lengths: long or short. This allows vehicle wiring to be reduced by the transmission and reception of
multiple signals over a single wire. The messages carried on Class II data streams are also prioritized. In other words, if two messages attempt to
establish communications on the data line at the same time, only the message with higher priority will continue. The device with the lower priority
message must wait. The most significant result of this regulation is that it provides scan tool manufacturers with the capability of accessing data from any
make or model vehicle sold in the United States.