For 1990-2009 cars

### 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.