2025 Audi A5 Volume Control Malfunction TSB U11B900

Owners of certain 2025 Audi models, including the A5, S5, Q5, and SQ5, may encounter issues with the vehicle's volume control and its associated background lighting. This problem prevents proper operation of the volume control, making it impossible to adjust audio levels, and also results in the background lighting for the control being non-functional. This specific concern is detailed in Audi Technical Service Bulletin (TSB) 2079999/1, released on November 10, 2025.

The TSB identifies the root cause as a software issue within the volume control system. Audi has implemented a production change in the third quarter of 2025 to address this defect in newly manufactured vehicles. However, existing vehicles produced before this change may still exhibit the symptoms and require a software update.

Symptoms

If your vehicle is affected by this issue, you will notice that the volume control knob or interface does not respond to inputs. This means you cannot adjust the audio volume for your infotainment system. Concurrently, the background lighting for the volume control will not illuminate, making it difficult to locate or operate in low-light conditions. These two symptoms typically appear together, indicating a communication problem with the volume control unit.

Fault Codes / DTCs

When diagnosing this issue, technicians will likely find a specific Diagnostic Trouble Code (DTC) stored in the vehicle's information electronics control unit, identified as J794 (diagnostic address 005F). The relevant fault code is:

• U11B900: "Volume control no communication, active/static"

This DTC confirms that the volume control unit is failing to communicate properly with the main information electronics system, leading to the observed operational and lighting malfunctions. The presence of this code is a key indicator for the Audi A5 volume control U11B900 problem.

Diagnosis and Trigger Conditions

Diagnosing this issue is straightforward. If a customer reports the volume control not working and the background lighting being off, a technician can easily reproduce the complaint. The primary diagnostic step involves scanning the vehicle's control units for stored fault codes. The presence of DTC U11B900 in the J794 control unit confirms the issue described in TSB 2079999/1. No specific environmental or operational conditions are noted as triggers; the issue is a persistent software fault.

Repair Procedure Summary

The resolution for the Audi A5 volume control U11B900 issue involves a software update. Audi Technical Service Bulletin 2079999/1 directs technicians to update the vehicle's software according to the instructions provided in another bulletin, TSB 2079690, titled "00 Combined software update 03.10.00/C (28.13.01) KD2." This update procedure typically requires connecting a battery charger to maintain stable voltage during the flashing process. The update encompasses preliminary and follow-up work, including managing the bus sleep cycle, performing a calibration drive, and potentially restarting the software update if the initial flashing attempt is aborted. The service number for this operation is 9110, with a damage code of KD02.

Important Warnings

Owners should be aware of the warranty implications for this repair. If your vehicle is outside of any applicable warranty, this Technical Service Bulletin is for informational purposes only. This means that the cost of the software update may not be covered by Audi, and you might be responsible for the repair expenses. It is always recommended to check your vehicle's warranty status with an authorized Audi dealer.

Owner Action

If you own a 2025 Audi A5, S5, Q5, SQ5, A6 Sportback e-tron, S6 Sportback e-tron, Q6 e-tron, or SQ6 e-tron and are experiencing a non-responsive volume control or non-illuminating background lighting, you should contact your authorized Audi dealer. Inform them of the symptoms and mention Audi Technical Service Bulletin (TSB) 2079999/1 and the DTC U11B900. The dealer will diagnose the issue and perform the necessary software update to resolve the Audi A5 volume control U11B900 problem. Ensure your vehicle's warranty status is confirmed before proceeding with any repairs to understand potential costs.

Source: NHTSA TSB ID 11026273