2021-2023 Audi 48V Electrical System Malfunction TSB 2058831/15

Audi has released Technical Service Bulletin (TSB) 2058831/15 to address a 48V vehicle electrical system warning that may appear in certain 2021-2023 Audi models. This bulletin specifically targets situations where the diagnostic trouble code (DTC) U046900 is stored in the Engine Control Module (ECM).

This TSB, identified as revision 15 and dated November 20, 2024, supersedes previous bulletin Group 27 number 24-72 from April 26, 2024. It provides updated warranty information, service procedures, and additional reference material for technicians.

Symptoms

Owners of affected Audi vehicles may observe the following symptoms related to this 48V electrical system issue:

• A warning message displayed on the instrument cluster stating, "Electrical system: malfunction! Please contact Service". This message is a direct indication of a problem within the vehicle's electrical system.
• A yellow or red battery warning symbol illuminated on the instrument cluster, signaling a potential issue with the vehicle's charging or battery system.

Fault Codes / DTCs

When diagnosing this issue, technicians may find the following diagnostic trouble codes (DTCs) stored in the vehicle's system:

• DTC U046900: This code is typically stored in the ECM (J623) or Gateway (J533) and signifies "Invalid data received from starter/generator control module" (symptom 36564).
• DTC B200096: This code, indicating a "Faulty control module," may be identified during the diagnostic process and points towards the need for starter-alternator replacement.

Diagnosis / Trigger Conditions

The 48V vehicle electrical system, which includes the Belt Starter Generator (BSG), is an intelligent system designed to provide electrical power as needed. Unlike traditional alternators, the BSG's output is regulated, making conventional diagnostic methods less effective. A hardware-related issue can cause the BSG to malfunction.

For proper diagnosis, technicians must use a VAS tester with the current version of ODIS. It is crucial to ensure both the 48V and 12V batteries are properly charged before proceeding with diagnostics. For guidance on charging the 48V battery, technicians are directed to TSB 2067906, titled "27 48V Reference: Charging 48V Battery with 12V Charger DTC P0A7D00/P0B2900."

During the diagnostic process, technicians will perform a function test called "C29 – Check Erase." This test involves specific ODIS paths depending on the vehicle model (Q7 vs. A6/A7/A8/Q8) to check and erase event memory entries related to the starter-alternator.

Important Warnings for Owners

Owners should be aware of specific conditions for this TSB to apply and what to expect during diagnosis:

• NOTICE: The DTC U046900 and the observed symptoms must precisely match the conditions described in TSB 2058831/15 for this bulletin to be relevant to your vehicle's issue.
• NOTICE: If DTC U046900 is not present in the test plan, or if the test plan indicates "The event memory could not be read," then the starter/generator is not considered faulty, and replacing parts will not resolve the problem.
• If your vehicle is outside of its warranty period, this Technical Service Bulletin is provided for informational purposes only, and repair costs may apply.

Repair Procedure Summary

If the diagnostic process confirms the presence of DTC U046900 and the test plan indicates DTC B200096 (Faulty control module), the primary repair involves replacing the starter-alternator (BSG) according to the procedures outlined in the ELSA repair manual. This repair addresses the underlying issue causing the "Electrical system: malfunction! Please contact Service" warning.

For warranty approval, several additional function tests must be completed and logged in the GFF Log. These include:

• De-energizing the 48V vehicle electrical system.
• Re-energizing the 48V vehicle electrical system.
• Performing the "00CC - Replace control module" procedure.
• Executing the "0001 - Coolant circuit bleeding procedure."

Failure to perform and document these necessary test plans may lead to the rejection of the warranty claim.

Warranty Information

Warranty claims for this issue are processed under Service Number 2726 and Damage Code 0040. Labor operations covered include:

• Replacing the starter-alternator (if required by TSB 2058831/15).
• Charging the 12V battery (if starter-alternator replacement is needed).
• General Function Test (GFF) operations, with time based on diagnostic protocol.

All warranty claims must adhere to the Audi Warranty Policies and Procedures Manual and are subject to review by Audi Warranty.

Related Bulletins

Technicians are advised that TSB 2067906, which provides guidance on charging the 48V battery, is a necessary reference for completing this procedure.

Owner Action

If you experience the "Electrical system: malfunction! Please contact Service" warning or see a battery warning light in your 2021-2023 Audi Q8, Q7, A7, A6, or A8, it is recommended to contact an authorized Audi service center. Inform them of the symptoms and mention the possibility of DTC U046900. The service center will perform the necessary diagnostic steps outlined in TSB 2058831/15 to accurately identify and resolve the issue with your 48V Mild Hybrid Electric Vehicle (MHEV) system.

Source: NHTSA ID: 11011249