Circuit Operation
There are two 
data lines that can be accessed with a scan tool. The UART data line (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 OBDII data line (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.