GM Service Manual Online
For 1990-2009 cars only

Circuit Description

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. Connecting a scan tool to the data link connector (DLC) allows communication with the modules for diagnostic purposes.

Diagnostic Aids

The following conditions will cause a total loss of class 2 serial data communication:

    • A class 2 serial data circuit shorted to ground.
    • A class 2 serial data circuit shorted to voltage.
    • An internal condition within a module or connector on the class 2 serial data circuit, that causes a short to voltage or ground to the class 2 serial data circuit.