Circuit Operation

DATA LINK CONNECTOR CIRCUIT DESCRIPTION
The serial data line is the means by which the microprocessor controlled modules in the vehicle communicate with the scan tool. There are three different types of serial data on this vehicle. They are: 1) Class 2 Serial Data, 2) keyword 82 Serial Data, and 3) keyword 2000 Serial Data

CLASS 2 DATA LINE
The Class 2 data line is powered by the control 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. Intermission is transmitted in bits, with each bit indicating status that is either low (zero volts) or high (7 volts). When no communication is occurring on the Class 2 data line, the line voltage is low (zero volts).

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:
^ Body Control Module (BCM)
^ Cellular Telephone
^ Radio, AM/FM Stereo and Clock and Tape Player and Compact Dick Player
^ Remote Control Door Lock Receiver
^ Sound Processor Interface

KEYWORD 82 AND KEYWORD 2000 DATA LINE
The keyword 82 and Keyword 2000 data lines are powered at a very low voltage by the control modules connected to them. As with Class 2, communication on the Keyword 82 and Keyword 2000 data lines occur on an "as-needed" basis, rather than being a continuous stream of data.

When the scan tool is connected to the data link connector, the scan tool provides 12 volts to the Keyword 82 and Keyword 2000 data lines. Each electronic control module transmits and receives messages composed of square wave signals by toggling the data line circuit. The result is that each bit indicates status that is either low (zero volts) or high (12 volts). When no communication is occurring, the Keyword 82 and Keyword 2000 data line voltage is low (zero volts). The control modules on the Keyword 82 data line are:
^ Automatic Level Control Sensor
^ Cruise Control Module
^ Driver Seat Adjuster Memory Module
^ Instrument Cluster
^ Heater and A/C Control
^ Inflatable Restraint Sensing and Diagnostic and Seat Belt Pretensioner Module
^ Power Steering Control Module
^ Sun Roof Actuator
^ Theft Deterrent Module

The control modules on the Keyword 2000 data line are:
^ Engine Control Module (ECM)
^ Transmission Control Module (TCM)
^ Electronic Brake/Traction Control Module

CIGAR LIGHTER/AUXILIARY OUTLET CIRCUIT DESCRIPTION
When the ignition switch is in the ON position, B+ is supplied to the front and console cigarette lighters through fuse #14. When the cigarette lighter knob is pushed in, the heater element warms up within a few seconds. After the heater element is warmed up, the knob is pushed out to indicate that it is ready for use. The front cigarette lighter is permanently grounded to G103 and the console cigarette lighter is permanently grounded to G200.