TSB: Mercedes Software Update

This bulletin applies to 2019 Mercedes-Benz models. The “SOS nonfunctional” message may display intermittently in the instrument cluster. The fault code B129C00 may be stored in the control unit log. The message usually occurs after the vehicle has been non-operational for an extended period of time (5 or more days). The message may then disappear after a few minutes. The cause may involve requiring a software update in the N112/9 control unit for telematics service to software release E522.7.