2021-2023 Audi 48V System Warning DTC U046900 TSB

Symptoms

Owners of affected Audi vehicles may notice a warning message displayed on the instrument cluster. This message typically states, "Electrical system: Malfunction. See owner's manual." In some cases, a yellow or red battery warning symbol may also illuminate on the dashboard. The German equivalent of the message, "Bordnetz: Störung! Bitte Service aufsuchen," may also appear.

Fault Codes / DTCs

When diagnosing the Audi 48V system warning U046900, technicians may find specific Diagnostic Trouble Codes (DTCs) stored in the vehicle's control modules:

• U046900: Invalid data received from starter/generator control module (symptom 36564). This code can be stored in the Engine Control Module (ECM, J623) or Gateway (J533).
• B200096: Faulty control module. This code indicates a potential issue with the starter-alternator itself.
• P0A7D00: This DTC is referenced in related TSB 2067906, concerning 48V battery charging.

Diagnosis / Trigger Conditions

To properly diagnose the Audi 48V system warning U046900, a technician must use a VAS tester with the current version of the ODIS diagnostic software. Before proceeding with diagnostics, it is crucial to ensure that both the 48V and 12V batteries are properly charged.

The diagnostic process involves performing a function test called "C29 – Check Erase" and attaching it to the test plan. The specific ODIS paths for this test vary by model:

• For Q7 models: Navigate through Body > Electrical system > 01 - On Board Diagnostic capable systems > CC - starter-alternator -C29 > CC - Functions > 00CC - Check/erase event memory entry.
• For A6, A7, A8, and Q8 models: Navigate through Diagnostic capable system > 00CC - starter alternator -C29 > 00CC - Functions > 00CC - Check/erase event memory entry.

During the test plan, if prompted whether the program is being run based on a Technical Service Bulletin, the answer should be YES.

Important Warnings

Audi has issued several critical notices regarding this issue:

• "The DTC and symptom must match for this TSB to apply." This means that both the specific warning message and the DTC U046900 must be present for this bulletin to be relevant.
• "A screenshot of ODIS with the VIN and DTC Memory Results from the test plan is necessary for billing under warranty." Owners should ensure their service center follows this procedure for warranty claims.
• "If the listed DTC is not stored in the test plan, then the generator is not faulty and replacing parts will not fix the problem." This prevents unnecessary parts replacement if the specific fault code B200096 is not identified.

Repair Procedure Summary

If, after performing the diagnostic function test, the event memory entry B200096 (Faulty control module) is found in ODIS, the starter-alternator should be replaced. This replacement should be performed according to the instructions in ETKA (Audi's electronic parts catalog) and the concern should be reevaluated afterward. The repair is covered under warranty, with a claim type of 110 for vehicles up to 48 months/50,000 miles, or G10 for CPO (Certified Pre-Owned) Covered Vehicles.

Required Tools or Parts

• VAS tester: Equipped with the current version of ODIS diagnostic software.
• Starter-alternator: Replacement part, if diagnosis confirms DTC B200096.

Owner Action

If your 2021-2023 Audi A6, A7, A8, Q7, Q8, A6 allroad, S8, or A8 L e displays an "Electrical system: Malfunction" warning or a battery warning light, and you suspect an Audi 48V system warning U046900, you should schedule an appointment with an authorized Audi service center. Provide them with details of the warning messages and any observed symptoms. The diagnosis and repair, if applicable, are typically covered under warranty for qualifying vehicles.

Superseded Bulletins

This Technical Service Bulletin, 2058831/12, supersedes Technical Service Bulletin Group 27 number 23-64, dated December 22, 2023.

Related Technical Service Bulletins

For additional information and context, technicians may refer to the following related TSBs:

• TSB 2067906: 27 48V Reference: Charging 48V Battery with 12V Charger DTC P0A7D00.
• TSB 2067937: 27 48V Reference: diagnosis and system information.

NHTSA ID: 10249233