Class II Serial Data Communications

Government regulations require that all vehicle manufacturers establish a common communication system. This vehicle utilizes "Class II" communication system. Each bit of information can have one of two lengths: long or short. This allows vehicle wiring to be reduced by transmitting and receiving multiple signals over a single wire. The messages carried on Class II data streams are also prioritized. If two messages attempt to establish communications on data line at same time, only message with higher priority will continue. The device with lower priority message must wait. The most significant result of this regulation is that it provides scan tool manufacturers with capability to access data from any make or model vehicle that is sold.

The data displayed on other scan tool will appear same, with some exceptions. Some scan tools will only be able to display certain vehicle parameters as values that are a coded representation of true or actual value. On this vehicle, scan tool displays actual values for vehicle parameters. It will not be necessary to perform any conversions from coded values to actual values.