Scan Tool Does Not Communicate With UART Data Line: Description

The UART Serial Data Line is used for communication with SIR Module. The UART line 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 with no communication taking place, the line voltage is approximately 5 volts. When data is transmitted the voltage is pulled to ground, approximately 0 volts. The supplemental inflatable restraint system Sensing and Diagnostic Module (SDM) utilizes UART communications. The scan tool may be used to retrieve, view, and clear Diagnostic Trouble Codes (DTC) stored in the SDM. The scan tool also uses the UART line to receive serial data from the SDM. A loss of UART communications would prevent the scan tool from communicating with the SDM during SIR system diagnosis.