2021 Mercedes-Benz AMG GT Poor Call Quality TSB

Owners of the 2021 Mercedes-Benz AMG GT may experience issues with call quality, where the person on the other end of a phone call has difficulty understanding the driver or hears excessive interference and background noise. This problem, often referred to as "Mercedes-Benz AMG GT poor call quality," tends to worsen as vehicle speed increases. Mercedes-Benz has released Technical Service Bulletin (TSB) L182.70-P-077433, version 3, dated March 5, 2025, to address these concerns.

This TSB, L182.70-P-077433, provides diagnostic information and a repair procedure for technicians to resolve the underlying causes of poor call quality.

Symptoms

Drivers of affected 2021 Mercedes-Benz AMG GT vehicles may notice the following symptoms related to the communication system:

• "Poor understanding" during mobile phone calls.
• "Driver cannot be heard" by the called party.
• "Driver can be poorly/hardly heard" during telephone conversations.
• "Driver's voice is difficult to understand when making telephone calls" due to interference or background noises.

Fault Codes / Damage Codes

Technicians may use the following damage codes when addressing this issue:

Cause

The TSB identifies several potential causes for the Mercedes-Benz AMG GT poor call quality:

• Improper Microphone Seating: The microphones (B25/20 or B25/21) in the headliner may not be seated correctly, with their side edges potentially covered by the textile material. This is illustrated in the TSB's "picture 1," which shows the microphone cutout not corresponding to specifications, leading to concealed side edges.
• Assembly Issues: Problems with the initial assembly of the B25/20 or B25/21 microphones in the headliner.
• Dirt Accumulation: Dirt inside the microphone housing can also impair performance.

Repair Procedure Summary

The repair for the Mercedes-Benz AMG GT poor call quality issue involves a precise adjustment and cleaning of the microphones. The procedure, which must be performed on both the B25/20 and B25/21 microphones, includes:

1. Accessing the microphone by pressing on its rear (where adhesive tape is located).
2. Carefully removing the microphone cap from the front.
3. Eliminating any protruding material residues around the microphone cutout in the headliner. This may involve using a soldering iron to ensure the cutout matches specifications, as depicted in "picture 2" where the side edges of the microphone are visible.
4. Pushing the microphone firmly into the headliner from behind until it is securely seated.
5. Maintaining pressure on the microphone while pressing and clipping the cap back into place. The cap should audibly and tactilely engage.
6. It is recommended to replace the cover caps during this procedure.

Technicians are also advised that the non-woven cloth within the cover cap is essential for protecting the microphone from dirt and should not be removed.

Important Warnings

Mercedes-Benz emphasizes that the information in TSB L182.70-P-077433 is intended for trained, professional technicians. It does not imply that a defect is present in any referenced vehicle or that a described repair applies to all vehicles. There can be multiple causes for similar symptoms, and technicians must use their diagnostic skills. This document does not guarantee warranty coverage nor does it extend the vehicle's warranty in any way.

Owner Action

If you are experiencing "Mercedes-Benz AMG GT poor call quality" or any of the described symptoms in your 2021 Mercedes-Benz AMG GT, it is recommended to schedule an appointment with an authorized Mercedes-Benz service center. Reference TSB L182.70-P-077433 when discussing the issue with your service advisor.

Source: NHTSA ID: 11015640