General Description

[1][2]DATA LINK COMMUNICATIONS CIRCUIT DESCRIPTION AND OPERATION
The Class 2 serial data link allows modules to transmit, receive, or exchange data.
^ The Electronic Brake Control Module (EBCM)
^ The Powertrain Control Module (PCM)
^ The radio (IRC)
^ The Vehicle Theft Deterrent (VTD)
^ The Vehicle Immobilizer Module (VIM)
^ The Inflatable Restraint Sensing and Diagnostic Module (SDM)

CIRCUIT DESCRIPTION
Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. In addition to this, Node Alive messages are transmitted by each module on the class 2 serial data circuit about once every 2 seconds. When the module detects the class 2 serial data circuit shorted, the setting of all other class 2 serial communication DTCs is inhibited and a U1300, U1301, or a U1305 DTC will set.

UNIVERSAL ASYNCHRONOUS TRANSMITTER RECEIVER (UART) DATA LINE
Circuit 799 exists pin 12 of the DLC, and is a dedicated communication link between the EBCM and the scan tool. When a communication failure exists with the EBCM, this circuit should be checked. This UART circuit can exist alone, or in conjunction with class 2 serial data communication information, depending on the vehicle, functions/RPOs.


The provision for communicating with the control module is a data link connector (DLC). The DLC is usually located under the instrument panel. The DLC is used in order to connect to a scan tool. Some common uses of the scan tool are listed below:
^ Identifying the stored diagnostic trouble codes (DTCs)
^ Clearing the DTCs
^ Performing the output control tests
^ Reading the serial data