C 1500 Truck 2WD V8-5.3L VIN T (1999)
Information Bus: Description and Operation
The serial data line is the means by which the microprocessor controlled modules in the vehicle communicate with other control modules and the scan
tool. There are 2 different types of communications used on this vehicle. They are:
^
Class 2 Serial Data
^
UART serial data
The class 2 data line is powered by the modules that are connected to it during operation. Communication on the class 2 data line occurs on an as needed
basis, rather than being a continuous stream of data. Information is transmitted in bits, with each bit indicating status that is either low (0 volts) or high (7
volts). When no communication is occurring on the class 2 data line, voltage is low.
Class 2 data is transmitted at a higher speed and messages are configured differently than UART data. While UART uses a master to control serial data
line traffic, class 2 uses the peer to peer method along with message arbitration to manage data line traffic. The control modules on the class 2 data line
are as follows:
^
Body control module (BCM)
^
Instrument cluster
^
Automatic transfer case (ATC) control module
^
Vehicle control module (VCM)
^
Powertrain Control Module (PCM)
^
Electronic Brake Control Module (EBCM). The inflatable restraint sensing and diagnostic module is the only module on the UART data line.
