2025 Audi A5/Q5/S5 Drive System Fault TSB 2079998/4

Audi has issued Technical Service Bulletin (TSB) 2079998/4 to address a "drive system fault" warning that may appear in the instrument cluster of certain 2025 Audi A5, Q5, and S5 models. This bulletin outlines a software update as the primary remedy for this condition, which can be triggered by specific diagnostic trouble codes (DTCs) related to the transmission. This TSB is crucial for owners experiencing the 2025 Audi A5 drive system fault.

Released on January 30, 2026, TSB 2079998/4 supersedes a previous bulletin, PSS TSB 2078847. It provides updated instructions and warranty information for technicians to resolve the 2025 Audi A5 drive system fault.

Revision History

This Technical Service Bulletin has undergone several revisions to ensure accuracy and provide the most current information:

• Revision 4: The header was revised to include updated software version details.
• Revision 3 (December 18, 2025): The header was revised to include updated model year information, and the warranty section was updated to reflect changes in labor operations.
• Revision 2 (November 10, 2025): The "Condition" section was revised to include corrected instructions for technicians.

Symptoms

Owners may observe the following symptom that indicates the 2025 Audi A5 drive system fault:

• A "drive system fault" warning lamp illuminates in the dash panel insert.
• In some cases, there may be no direct customer complaint, but diagnostic checks reveal underlying issues.

Fault Codes / DTCs

Technicians diagnosing the 2025 Audi A5 drive system fault may find the following event memory entries logged in the gearbox electronics control unit (J217) at diagnostic address 0002:

Code	Description	Symptom
P071100	"Transmission Fluid Temperature Sensor "A" Circuit Range/Performance"	20756
P270800	"Solenoid Valve 6 is sticking on"	20859

These codes indicate specific issues within the transmission system that trigger the warning lamp.

Diagnosis and Trigger Conditions

Before performing any repair, technicians are instructed to try and reproduce the customer complaint. This ensures that the observed issue aligns with the conditions described in TSB 2079998/4. The repair detailed in this bulletin must only be carried out if all vehicle-specific criteria are met. These criteria include the exact model/type, chassis number, engine/motor and gearbox code, PR number(s), part number, and software version.

Failure to strictly adhere to these criteria may result in the problem persisting, necessitating repeat repairs, and potentially leading to warranty claim rejections by Audi.

Repair Procedure Summary

The primary repair for the 2025 Audi A5 drive system fault involves a combined software update. Technicians should first verify if TSB 2079690, titled "00 Combined software update 03.10.00/C (28.13.01) KD2," is applicable and visible for the specific vehicle. If this prerequisite TSB applies, the software update described within TSB 2079690 must be performed.

The engine control unit software requires updating. This process includes connecting a battery charger to the vehicle to ensure stable voltage throughout the update procedure. This software update is designed to optimize the vehicle's systems and resolve the underlying causes of the "drive system fault" warning.

Important Warnings for Owners

• Warranty Coverage: If your vehicle is outside of its warranty period, this Technical Service Bulletin is informational only. This means that the repair may not be covered free of charge, and you might be responsible for the costs.
• Chip Tuning Risks: Audi explicitly warns that updating the engine control unit software will render any existing chip tuning ineffective. Furthermore, in certain circumstances, performing the software update on an engine control unit that has been chip-tuned could potentially damage the unit. Owners who have modified their vehicle with chip tuning are advised to consult with their tuning company in advance to determine if a software update is possible. Damage to the engine control unit resulting from chip tuning cannot be billed to AUDI AG under warranty. Audi recommends referring to the Warranty and Maintenance booklet for more details on how chip tuning can impact warranty coverage.
• Manufacturer Responsibility: Neither AUDI AG nor your dealership can be held responsible for damage caused by the software update itself or for damage that occurs as a result of not having the update performed. It is crucial to have a note to this effect on the repair order, signed by the customer, and included in the customer's vehicle file.

Warranty Information

For vehicles still under warranty, the repair for the 2025 Audi A5 drive system fault is covered. The designated service number for this operation is 3730, and the damage code is KD02. Specific labor operations and time units (TU) are allocated for the software update process:

• Labor Operation 0151 0010: This covers the software update itself, including the necessary step of connecting a battery charger. Technicians should refer to the Service Repair Time (SRT) guide for associated operations.
• Labor Operation 0151 0040: This is a fixed rate for the software update, encompassing all required preliminary and follow-up work. This includes procedures such as the bus sleep cycle, calibration drives, and any additional work. This operation is allocated 130 time units.
• Labor Operation 0150 9999: In cases where additional attempts are required due to flash cancellation, an additional lump sum of 50 time units is provided per each documented attempt.

All warranty claims submitted for payment must strictly adhere to the guidelines outlined in the Audi Warranty Policies and Procedures Manual. Claims are subject to review or audit by Audi Warranty. When performing a combined software update, time stamps are not required for billing under warranty, allowing technicians to work on other vehicles simultaneously. Non-productive personnel are also permitted to perform the combined software update.

Owner Action

If you experience a "drive system fault" warning in your 2025 Audi A5, Q5, or S5, or if you encounter diagnostic trouble codes P071100 or P270800, it is strongly recommended to contact an authorized Audi dealer. They are equipped to diagnose the issue accurately and perform the necessary software update as outlined in TSB 2079998/4. For vehicles covered under warranty, this repair should be performed free of charge. Be prepared to discuss any prior chip tuning modifications with your dealer.

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Source: NHTSA ID: 11028472