2021 Mercedes-Benz AMG GT SOS Non-Functional Message

Symptoms

Owners of the 2021 Mercedes-Benz AMG GT may encounter a sporadic warning message in their instrument cluster stating "SOS nonfunctional". This message typically appears after the vehicle has been non-operational for an extended period of time. The "AMG GT SOS non-functional" message usually disappears on its own after a few minutes.

Alongside this visual warning, the diagnostic trouble code (DTC) B129C00 is stored in the vehicle's control unit log. This indicates a detected malfunction within the telematics services system. The issue is noted to affect all Mercedes-Benz model series equipped with SA code 360/362, which pertains to specific navigation and communication systems.

Fault Codes / DTCs

The primary fault code associated with the "SOS nonfunctional" message is B129C00. This code specifically points to a malfunction within the N112/9 control unit, which is responsible for telematics services. Technicians will find this code stored in the control unit log when diagnosing the issue.

Cause of the Issue

The root cause of the "AMG GT SOS non-functional" message and the associated DTC B129C00 is identified as a software error. Specifically, the N112/9 control unit for telematics services, also known as HERMES, contains a software bug. This error leads to the incorrect and sporadic display of the warning message "SOS nonfunctional" in the instrument cluster.

Important Warnings for Owners

Mercedes-Benz emphasizes that despite the appearance of the "SOS nonfunctional" message, there is no functional limitation to the emergency call system to be expected. This means that the vehicle's ability to contact emergency services in a critical situation remains fully operational, even when the warning is displayed.

Owners should also be aware that if, against expectations, the erroneous display of the "SOS nonfunctional" message in the instrument cluster continues to occur following the software update, technicians are instructed to create a TIPS case for further investigation. This ensures that persistent issues are escalated for a more in-depth review.

Repair Procedure Summary

The resolution for the "SOS nonfunctional" message and DTC B129C00 involves a straightforward software update. Authorized Mercedes-Benz technicians will update the N112/9 control unit for telematics services (HERMES) to software release E522.8. This update is designed to correct the underlying software error that causes the warning message to appear. The procedure typically involves connecting the vehicle to diagnostic equipment and flashing the new software version to the control unit.

Warranty Information

For dealership technicians, the internal damage code associated with this repair is 8209Z. This code is used for warranty claims related to addressing the B129C00 fault and the "SOS nonfunctional" message.

What Owners Should Do

If you own a 2021 Mercedes-Benz AMG GT or any other applicable Mercedes-Benz model and are experiencing the "SOS nonfunctional" message or have had DTC B129C00 stored in your vehicle's system, you should schedule an appointment with an authorized Mercedes-Benz dealership. The software update is the recommended remedy to address this issue and restore normal operation of the instrument cluster display.

NHTSA ID: 10244837