UART

The UART serial data communication relies on a 5 volt digital signal for the exchange of data between different control modules and to provide scan tool diagnostic data. When the ignition switch is in the RUN position and the UART line is at rest, i.e. no communication taking place, the voltage remains HIGH at approximately 5 volts. When data is transmitted the voltage is cycled to ground, approximately 0 volts.

The supplemental inflatable restraint system's Sensing And Diagnostic Module (SDM) utilizes UART communications. The SDM uses UART serial data to allow communication with a scan tool for diagnostic purposes. Diagnostic Trouble Codes (DTCs) stored by the SDM can be retrieved, viewed and cleared with the use a scan tool. A loss of UART communications would prevent the scan tool from communicating with the SDM during SIR system diagnosis.