2022-2024 Audi A3/S3/RS3 Exterior Lighting Warning TSB 2074786/3

Owners of 2022-2024 Audi A3, S3, RS3, Q4 e-tron, and Q4 Sportback e-tron vehicles may encounter an unexpected "Warning lamp for exterior lighting" or adaptive light message in their instrument cluster. This issue, despite the warning, typically occurs when the vehicle's lighting system appears to be functioning correctly. This article details Audi TSB 2074786/3, which provides diagnostic and repair information for this specific concern, often linked to a software issue within the light switch or related components.

The Audi S3 exterior lighting warning is an intermittent fault that can be temporarily resolved by pressing the "AUTO" button on the light switch module, which causes the warning lamp to disappear and the associated Diagnostic Trouble Code (DTC) to become intermittent.

Symptoms

The primary symptom owners will notice is a "Warning lamp for exterior lighting" or "adaptive light is displayed in the instrument cluster" message in their vehicle's instrument cluster. This warning appears despite the exterior lighting system seemingly working without any functional problems. The issue is described as occurring "only very occasionally." A temporary fix involves "Pressing the 'AUTO' button on the light switch module remedies the fault immediately and causes the warning lamp to go out."

Fault Codes / DTCs

When this Audi S3 exterior lighting warning occurs, specific Diagnostic Trouble Codes (DTCs) are typically stored in the onboard supply control unit J519 (address 0009). These codes help technicians pinpoint the nature of the fault:

Code	Description
B126A29	Light switch implausible signal
U112100	Data bus missing message
U110B00	Light switch no communication

Diagnosis / Trigger Conditions

Workshop findings confirm that the concern can be reproduced, and the presence of the aforementioned DTCs in the onboard supply control unit J519 (address 0009) is a key diagnostic indicator. The TSB notes that pressing the "AUTO" button on the light switch module will cause the warning lamp to go out and change the DTC entry from static to intermittent. If the DTC can then be successfully deleted, it indicates an intermittent issue that may not require immediate part replacement. However, if the DTCs, particularly U112100, U110B00, or B126A29, remain static and cannot be cleared, it suggests a more persistent problem requiring component replacement of the light switch.

Repair Procedure Summary

Audi Technical Service Bulletin 2074786/3 outlines the repair process for the Audi S3 exterior lighting warning. The production solution involves installing a new light switch, which comes with optimized software version 0013 and new part indexes AC or AD, depending on the specific vehicle type.

The service procedure begins by checking whether the situation matches the description provided in the TSB. Technicians are instructed to observe if pressing the "AUTO" button on the light switch causes the warning lamp to go out and changes the DTC entry to intermittent. If this occurs, the DTC can then be deleted. If, however, it is not possible to delete the DTC and the entry remains logged as static, the light switch must be replaced.

For replacement, the labor operation involves removing and installing the main light switch, identified by labor code 9405 19xx. This also includes performing Guided Functions (GFF) with labor code 0150 0060, with labor time billed according to the diagnostic log. If replacing the switch is not necessary, but repair is still required, the labor operation for repairing the light switch is 9405 4199, billed according to the time required, along with Guided Functions (0150 0010 and 0150 0060). This TSB closes a previous bulletin, PSS 20373612, indicating an updated and definitive solution for the "94 PSS Headlight warning in cluster, DTC : B126A29, U110B00 stored in 09 module."

Important Warnings

Owners and technicians should be aware of a critical distinction: "If only DTC 'U110B00 Light switch no communication' is stored without the other entries," meaning B126A29 and U112100 are not present, "the cause may be a loose connector, a pin that has been pushed back or a wiring problem." In such cases, investigating these potential wiring issues is crucial before proceeding with a light switch replacement, to prevent unnecessary part replacement and ensure the correct root cause is addressed.

Required Tools or Parts

The production solution for this issue involves installing a new light switch. This new light switch comes with optimized software, specifically version 0013, and is identified by new part indexes AC or AD, depending on the vehicle type. Technicians will need to ensure they order the correct light switch part number based on the vehicle's specifications to address the Audi S3 exterior lighting warning effectively.

Warranty Information and Revision History

This Technical Service Bulletin 2074786/3 provides detailed guidance for warranty claims under Service Number 9405 and Damage Code 0040. For vehicles outside of any warranty, this TSB is for informational purposes only. Audi specifies that replacement and repair labor operations cannot be claimed together; only the necessary operation should be billed. All warranty claims must adhere to the Audi Warranty Policies and Procedures Manual and are subject to review or audit by Audi Warranty. The claim comment for this TSB is "As per TSB 2074786/3".

The bulletin has undergone several revisions to refine the diagnostic and repair procedures:

• Revision 3 (Release date: December 11, 2025): This revision updated the service procedure and revised the warranty table.
• Revision 2 (Dated: September 26, 2025): This revision updated the condition description and the production solution, including updates to software and part number indexes.
• Revision 1 (Dated: August 01, 2024): This was the initial publication of the bulletin.

Owner Action

If you experience an Audi S3 exterior lighting warning or similar messages in your 2022-2024 Audi A3, S3, RS3, Q4 e-tron, or Q4 Sportback e-tron, it is recommended to contact an authorized Audi service center. While pressing the "AUTO" button on the light switch may temporarily clear the warning, a permanent solution often requires diagnosis and potential replacement of the light switch module as outlined in Audi TSB 2074786/3. Be prepared to describe the symptoms and any temporary fixes you've attempted.

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Source: NHTSA ID: 11027357