2021 Mercedes-Benz AMG GT Red Battery Warning TSB

Owners of the 2021 Mercedes-Benz AMG GT (W190 chassis code) may encounter a "red battery warning" message in their instrument cluster while driving. This issue is addressed by Technical Service Bulletin (TSB) LI54.10-P-076742, issued on July 25, 2023.

Symptoms

The primary symptom described in the TSB is "The red battery light in the instrument cluster lights up while driving." This warning is specifically identified as the "Battery charge indicator/consumer shutoff > Illuminates red." This indicates a problem within the vehicle's electrical system related to power supply and battery charging.

The underlying cause for the Mercedes-Benz AMG GT red battery warning is a voltage drop. This voltage drop can occur in one of three critical areas: the alternator, the main battery, or the chassis main circuit. Such a drop can prevent the battery from charging correctly or impact the overall electrical stability of the vehicle.

Diagnosis and Trigger Conditions

Diagnosing the Mercedes-Benz AMG GT red battery warning involves a systematic check of the vehicle's electrical components. The TSB highlights that improper ground connections are a common cause, explicitly showing images of "Ground connection not permissible" in various locations. Technicians are instructed to carefully inspect these ground points.

Additional diagnostic steps include:

• Battery Test: The state of charge of the battery must be tested. If the battery is found to be faulty or unable to hold a charge, it should be replaced.
• Fuse Box Inspection: The fuse box f32/2 needs to be checked thoroughly for any signs of water intrusion, oxidation, or physical damage that could disrupt electrical flow.
• Alternator Check: The alternator and its management system require verification for correct functionality using the Mercedes-Benz Xentry diagnostic system.
• Software Update: The front and rear Signal Acquisition and Actuation Modules (SAM) may require a software update to ensure proper communication and function within the electrical system.

Repair Procedure Summary

The repair process for the Mercedes-Benz AMG GT red battery warning focuses on identifying and rectifying the source of the voltage drop. The first critical step is to inspect all ground points, comparing them against reference pictures and guides, such as those found in the Massenstellen.pdf and Grounding locations M178_BR190_engl.pdf documents.

Following the ground point inspection, technicians will proceed with testing the battery's condition and replacing it if necessary. A detailed examination of fuse box f32/2 for any damage or corrosion is also part of the procedure. The functionality of the alternator and its associated management system will be verified using the Xentry diagnostic tool. Finally, software updates for the front and rear SAM units are performed.

If the red battery warning persists after these checks and replacements, technicians are advised to read out the on-board electrical system data and open a TIPS case. This allows for further technical assistance from Mercedes-Benz, providing detailed results and pictures of the performed checks.

Required Tools or Parts

To address the red battery warning, technicians may require specific parts and diagnostic equipment:

• Diagnostic System: Mercedes-Benz Xentry system for checking alternator management and updating SAM modules.
• Reference Documents: Massenstellen.pdf and Grounding locations M178_BR190_engl.pdf for proper ground point identification and inspection.

Potentially required replacement parts include:

• Starter battery: Part number A0009826205
• Alternator: Part number A0009061705
• Fuse box (F32/3): Part number A2125407150

Owner Action

If you experience the "red battery warning" or "Battery charge indicator/consumer shutoff > Illuminates red" message in your 2021 Mercedes-Benz AMG GT, it is recommended to contact your authorized Mercedes-Benz dealership. They have the necessary diagnostic tools and technical information, including TSB LI54.10-P-076742, to accurately diagnose the voltage drop issue and perform the appropriate repairs. Since this is a technical service bulletin, the repair may be covered under warranty, depending on your vehicle's specific warranty coverage and mileage.

NHTSA ID: 10240161