UART Data Line

The UART serial data communication relies on a 5-volt digital signal for the exchange of data between different control modules and a scan tool. When the ignition is in RUN and there is no data transmission, there is a constant 5 volts on the data line. Communication on the line brings the voltage to 0 volts. The supplemental restraint Sensing and Diagnostic Module (SDM) communicates on the UART data line.