Class II Serial Data Communications

Class II Serial Data Communications

Government regulations require that all vehicle manufacturers establish a common communication system. This vehicle utilizes the "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 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 to access data from any make or model vehicle that is sold.

The data displayed on the other Scan Tool will appear the same, with some exceptions. Some Scan Tools will only be able to display certain vehicle parameters as values that are a coded representation of the true or actual value. For more information on this system of coding, refer to Decimal/Binary/Hexadecimal Conversions.

On this vehicle the Scan Tool displays the actual values for vehicle parameters. It will not be necessary to perform any conversions from coded values to actual values.