Test B: Scan Tool Does Not Communicate With Class 2 Device: Description
WARNING: This page is about a different car, the 2002 Pontiac Sunfire, 2002 Chevrolet Cavalier, 2001 Pontiac Sunfire, and 2001 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
Modules connected to class 2 serial data circuit monitor serial data communications during normal vehicle operation. Operating information and commands are exchanged between modules. Connecting scan tool to Data Link Connector (DLC) allows communication with modules for diagnostics. Engine will not start when there is a complete malfunction of class 2 serial data line while engine is off.