Circuit Operation
There are two 
data lines that can be accessed with a scan tool. The 
Serial Data Line (
UART) (800 CKT) allows the scan tool (when connected), 
Powertrain Control Module (PCM), Instrument Cluster 
(I/P), Diagnostic Energy Reserve Module 
(DERM), and the Electronic Brake Control Module 
(EBCM) to communicate via serial data. The Serial Data Line (Class 2) (1807 CKT) allows a scan tool to directly access the Powertrain Control Module to read emissions related information. A scan tool can gain access to both data lines through the Data Link Connector 
(DLC). System operations can then be monitored or controlled for diagnostic purposes.