2022-2023 Audi A3, S3, RS 3 Electrical System Fault TSB

Owners of 2022-2023 Audi A3, S3, and RS 3 models may encounter a dashboard warning message stating "Electrical system: fault. Let engine run with vehicle stationary. See owner's manual" accompanied by a yellow or red battery symbol warning lamp. This issue, detailed in Audi Technical Service Bulletin (TSB) 2074792/1, points to a software-related problem within the vehicle's 48V electrical system.

This TSB, identified as 27 24 79 2074792/1, provides guidance for diagnosing and resolving the Audi S3 electrical system fault and related battery warnings. It's crucial for owners to understand the implications of these warnings and the recommended actions to prevent potential vehicle issues.

Symptoms You Might Notice

If your 2022-2023 Audi A3, S3, or RS 3 is affected, you will typically observe one or both of the following indicators:

• A specific message displayed in the instrument cluster: "Electrical system: fault. Let engine run with vehicle stationary. See owner's manual". This message instructs the driver to keep the vehicle stationary while the engine runs.
• The battery symbol warning lamp illuminating in either yellow or red. A red light usually indicates a more critical condition than a yellow one.

Technical Background

The root cause of this Audi S3 electrical system fault and the associated battery warning lamps is identified as a software issue within the Battery Management 2 control module. This module, accessible via diagnostic address 0021, is responsible for managing the vehicle's 48V battery system. An outdated or faulty software version can lead to incorrect readings or management of the battery's charge level, triggering the warning messages.

Important Warnings for Owners

Audi has provided specific instructions for owners when the battery warning lamp appears, especially while driving. It is critical to follow these guidelines to ensure safety and prevent further issues:

• If the warning lamp (battery symbol) lights up in red while driving, indicating a critically low 48V battery charge, you must park the vehicle safely. Switch the ignition off and then on again. The warning lamp should then turn yellow. You must then let the engine run with the vehicle stationary until the warning lamp goes out. Do not drive off until the warning lamp has gone out.
• If the warning lamp (battery symbol) lights up in yellow while driving, also indicating a low 48V battery charge, you should park the vehicle safely. Let the engine run with the vehicle stationary until the warning lamp goes out. Do not drive off until the warning lamp has gone out.

Repair Procedure Summary

For technicians, the service procedure outlined in TSB 2074792/1 involves several steps to address the Audi S3 electrical system fault:

1. Check for Outstanding Campaigns: Before any diagnostic work, technicians are instructed to check for any outstanding field campaigns, particularly service campaign 9309. Any such campaigns should be completed first.
2. Guided Fault Finding: If the 48V battery is discharged, technicians must work through the event memory entries in diagnostic address 0021 using Guided Fault Finding procedures.
3. Software Update: The primary solution involves updating the software for the Battery Management 2 control module. This update aims to correct the underlying software issue causing the fault.
4. Owner Guidance: If the "Electrical system: fault. Let engine run with vehicle stationary. See owner's manual" message is present, technicians are to advise owners on the proper procedure for addressing the yellow or red battery warning lamp, as detailed in the