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 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.
