2021 Mercedes-Benz AMG GT SOS Not Activated Message TSB

Owners of certain 2021 Mercedes-Benz AMG GT gray import vehicles may encounter a persistent warning message in their instrument cluster: "SOS - Service not activated". This issue typically arises after a software update to the HERMES communication module N112/9. This technical service bulletin (TSB) L182.85-P-079271, issued on May 22, 2025, outlines the cause and the recommended remedy for this specific problem.

Symptoms

The primary symptom is the dashboard message "SOS - Service not activated" displayed prominently in the instrument cluster. This indicates that the vehicle's telematics services, including the emergency call function, are not operational. Owners may also notice related issues such as:

• Internet services being unavailable.
• No connection possible for telematics services.
• A general warning message related to the emergency call function.

Cause of the "AMG GT SOS not activated" message

The root cause of the "AMG GT SOS not activated" message in gray import vehicles is the inability of the HERMES communication module's SIM card to establish a connection with the local mobile phone network in the importing country. This prevents the vehicle from performing the necessary "over-the-air" registration with the Mercedes Intelligent Cloud. Vehicles equipped with HERMES communication module codes 360, 362, or 364 are specifically affected.

Important Warnings

It is crucial for owners and technicians to understand that replacing the hardware of the HERMES communication module is not effective in resolving this issue. The problem lies with the SIM card's network compatibility in gray import vehicles, not a faulty hardware component.

Repair Procedure Summary

The only way to address the "AMG GT SOS not activated" message and prevent its display is to deactivate the HERMES module. This deactivation process, identified as the 090 deactivation, requires the customer's consent. Once the HERMES control unit (N112/9) is deactivated, its operating status will change to "Inoperative".

Following deactivation, the message "SOS not ready" will appear in the audio/COMAND display (A40/8) and potentially in the instrument cluster. This message serves as a notification to the customer that the emergency call function is no longer available. Additionally, the workshop must affix a specific label to both the cover of the emergency call button in the overhead control panel and to the emergency call button itself.

Required Tools or Parts

For the deactivation procedure, the primary required part is the label that must be attached to the emergency call button. The part number for this label is A9078172900.

Owner Action

If you own a 2021 Mercedes-Benz AMG GT gray import vehicle and are experiencing the "SOS - Service not activated" message, you should contact an authorized Mercedes-Benz service center. They can perform the HERMES module deactivation as outlined in TSB L182.85-P-079271. Be aware that this procedure will disable the emergency call function and related telematics services.

---

Source: NHTSA ID 11018626