2025 Audi A5 Assist System Warning Messages TSB 2079757/1

Owners of certain 2025 Audi models, including the A5, S5, Q5, and SQ5, may encounter various warning messages related to their vehicle's assist systems. Audi Technical Service Bulletin (TSB) 2079757/1, released on October 21, 2025, provides detailed diagnostic and repair information for these issues, specifically for PPE/PPC vehicles in the United States market.

This TSB addresses situations where multiple driver assistance systems display fault messages, often linked to a communication issue within the vehicle's data bus system. The primary diagnostic trouble code (DTC) associated with this problem is U171200, indicating a communication failure with the driver assistance main control module. If you are experiencing a 2025 Audi A5 assist system warning, this document outlines the common symptoms, diagnostic steps, and the prescribed repair.

Symptoms of Assist System Malfunction

If you own a 2025 Audi A5, S5, Q5, or SQ5, you might observe one or more of the following warning messages or indicators related to your assist systems, typically displayed in the instrument cluster:

• "Adaptive cruise assist: fault."
• "Emergency assist: fault."
• "Lane departure warning: fault."
• "Adaptive front assist, distance warning: fault."
• "Traffic sign recognition: fault."
• "Adaptive light: fault."
• "Main beam assist: fault."
• "Driver assist systems currently restricted."

These warnings indicate a malfunction across several driver assistance features, suggesting a broader communication problem rather than an isolated component failure. The presence of a 2025 Audi A5 assist system warning often points to the underlying issue described in this bulletin.

Fault Codes / DTCs

Technicians investigating a 2025 Audi A5 assist system warning will likely find specific diagnostic trouble codes (DTCs) logged in the vehicle's control modules. The key DTC associated with this issue is:

• U171200: Driver assistance main control module Ethernet data bus, no communication, active/static with symptom 4540

This DTC is typically logged in diagnostic address 0019, which corresponds to the data bus on-board diagnostic interface. Furthermore, during diagnosis, technicians may find that diagnostic addresses 00A5 (Front sensor for driver assistant system) and 8103 (Main control module driver assistance) cannot be accessed, further confirming the communication fault.

Diagnosis and Trigger Conditions

According to TSB 2079757/1, the complaint of a 2025 Audi A5 assist system warning is specifically applicable if three conditions are met simultaneously during workshop findings:

1. There are active warning messages related to assist systems present in the instrument cluster.
2. Diagnostic addresses 00A5 (Front sensor for driver assistant system) and 8103 (Main control module driver assistance) cannot be accessed via the diagnostic system (ODIS).
3. DTC "U171200 / 4540" is logged in diagnostic address 0019 (Data bus on board diagnostic interface).

If these specific conditions are not met, the issue may stem from a different cause, and this TSB would not apply. If the warning messages are not currently active, technicians are advised to check the event memory for the passive/intermittent status of DTC "U171200: Driver assistance main control module Ethernet data bus, no communication, passive/intermittent with symptom 4540". They should also refer to the date, time, and frequency counter in the ambient conditions to determine if the logged fault corresponds to the customer's reported complaint.

Important Warnings for Owners and Technicians

This Technical Service Bulletin includes a critical caution regarding the applicability of the repair. For the procedures outlined in TSB 2079757/1 to be relevant, the following conditions must all be present:

• There are active warning messages displayed in the instrument cluster.
• Diagnostic addresses 00A5 and 8103 cannot be accessed by the diagnostic tool.
• DTC "U171200 / 4540" is logged in diagnostic address 0019.

If any of these conditions are not met, the TSB does not apply, and a different diagnostic approach will be necessary. This ensures that the correct root cause is identified and addressed, preventing unnecessary repairs.

Repair Procedure Summary

The root cause of the 2025 Audi A5 assist system warning and DTC U171200 is identified as a fault within the data bus diagnostic interface. The prescribed solution outlined in Audi TSB 2079757/1 involves replacing this component, which is located at diagnostic address 0019.

When performing the repair, technicians are required to document the complaint thoroughly for billing and parts analysis purposes. This documentation must include clear photos or videos that prominently show the complaint. The visual evidence must:

• Include the vehicle's VIN and the date.
• Be unedited.
• Be in focus and taken with sufficient light.
• Avoid showing any people, faces, license plates, or customer data.

If appropriate, technicians should also mark the location of the problem in the photos to provide a clear reference for parts analysis. After replacing the data bus diagnostic interface, the vehicle's battery should be charged, and a Guided Fault Finding (GFF) procedure should be performed.

Warranty Information

For warranty claims related to this 2025 Audi A5 assist system warning, the following codes and procedures apply, provided the vehicle is still under warranty. If the vehicle is outside of any warranty, this Technical Service Bulletin serves as informational guidance only.

• Service Number: 9035
• Damage Code: 0040
• Labor Operations:
  • 9035 19xx: Data bus control unit removed and installed (refer to Service Repair Time (SRT) for associated operations)
  • 2706 8950: Charge battery (refer to SRT for associated operations)
  • 0150 0060: GFF (Time stated on the diagnostic protocol)
• Claim Comment: As per TSB 2079757/1

All warranty claims submitted for payment must be in accordance with the Audi Warranty Policies and Procedures Manual and are subject to review or audit by Audi Warranty. Technicians are advised to always check with their Parts Department and/or ETKA for the latest information and parts bulletins, as all part and service references provided in this TSB (2079757) are subject to change and/or removal.

Source: NHTSA ID 11025359