2025-2026 Audi Driver Assist System Fault TSB

Owners of certain 2025-2026 Audi A5, A6, Q5, S5, and SQ5 models may experience various fault messages related to the driver assist systems, along with a 'take over steering prompt' appearing on the instrument cluster shortly after starting the vehicle. This issue is detailed in Audi Technical Service Bulletin (TSB) 2081344/1, titled "90 PPE/PPC: KD1 - fault messages relating to driver assist systems - U171200."

This TSB addresses a software problem within the data bus diagnostic interface control unit, J1273, which can lead to a range of driver assistance features becoming restricted or unavailable. The Audi driver assist system fault U171200 is a key indicator of this condition.

Symptoms

If your vehicle is affected, you may observe the 'take over steering warning light' illuminated on your instrument cluster. Additionally, depending on the specific equipment installed in your Audi, you might see one or more of the following verbatim fault messages:

• "Adaptive cruise assist: fault. You can continue driving"
• "Lane departure warning: fault. You can continue driving"
• "Active front assist / distance warning: fault. You can continue driving"
• "Traffic sign recognition: fault. You can continue driving"
• "Adaptive light: fault"
• "Main beam assist: fault"
• "Lane change assist: currently unavailable"
• "Proactive occupant protection: currently unavailable"
• "Driver assist systems currently restricted"
• "Emergency Assist: fault. You can continue driving"

These messages typically appear only shortly after starting the vehicle and may resolve themselves after a bus sleep cycle, which occurs when the ignition is switched off, the vehicle is locked, and approximately three minutes have passed.

Important Notices

Audi has issued specific conditions under which TSB 2081344/1 applies. Owners should be aware of the following:

• This TSB does NOT apply if the red warning lamp for the 'take over steering prompt' is not active.
• This TSB does NOT apply if only some of the fault messages listed above have occurred or are active.
• The TSB is NOT applicable if notifications are displayed stating various driver assist systems are not available due to restricted visibility (e.g., due to snow, ice, or dirt on sensors).

Fault Codes / DTCs

The primary diagnostic trouble code (DTC) associated with this issue is U171200. This code can be logged in the Data Bus On Board Diagnostic Interface, J1273 (diagnostic address 0019), and may appear with different symptom bytes:

• U171200: "Driver assistance main control module, no communication, active/static with symptom 4540"
• U171200: "Driver assistance main control module, no communication, passive/intermittent with symptom 4540"

For this TSB to apply, technicians must confirm that diagnosis via ODIS for diagnostic addresses 00A5 and 8103 is not possible, meaning these addresses cannot be read out. The presence of active warnings and a logged event memory entry are also crucial for confirming the complaint.

Diagnosis / Trigger Conditions

To accurately diagnose the Audi driver assist system fault U171200, the customer complaint must be reproducible in the workshop. This means active warning messages must be present in the instrument cluster, and diagnostic addresses 00A5 and 8103 must be inaccessible. Additionally, a specific event memory entry must be logged.

The issue is a software fault in the data bus diagnostic interface control unit (J1273) that occurs shortly after ignition. It typically affects only one driving cycle and is temporarily remedied by a terminal 30 reset of the J1273 unit or by the vehicle entering a bus sleep cycle. A bus sleep cycle is achieved by turning off the ignition, locking the vehicle, and waiting for about three minutes.

Repair Procedure Summary

The recommended repair for the Audi driver assist system fault U171200 involves a software update. Technicians are instructed to perform TSB 2079690, which details the "00 Combined software update 03.10.00/C (28.13.01) KD2." This update is designed to resolve the underlying software issue in the J1273 control unit.

During the software update, it is necessary to connect a battery charger to maintain stable voltage. The repair process includes the software update itself, along with all required preliminary and follow-up work, such as calibration drives and additional necessary steps.

Warranty Information

For vehicles still under warranty, claims for this repair should be submitted in accordance with the Audi Warranty Policies and Procedures Manual. The service number for this operation is 9035, with a damage code of KD02. Labor operations include 0151 0010 for the software update with battery charger, 0151 0040 for the fixed rate software update, and 0150 9999 for additional attempts if a flash abort occurs.

If the vehicle is outside of its warranty period, this Technical Service Bulletin is informational only, meaning the repair costs may not be covered by Audi.

Owner Action

If you are experiencing these driver assist system fault messages or the 'take over steering prompt' in your 2025-2026 Audi, it is recommended to schedule an appointment with an authorized Audi service center. Be prepared to describe the exact fault messages you are seeing and when they occur. The technicians will use TSB 2081344/1 to diagnose and apply the necessary software update.

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Source: NHTSA ID: 11031046