2025-2026 Audi A5/Q5/S5/SQ5 Drive System Fault P066700

Audi has released Technical Service Bulletin (TSB) 2080075/2 to address a specific issue affecting certain 2025-2026 Audi A5, S5, Q5, and SQ5 models. Owners may experience a 'drive system fault' warning light illuminating in the instrument cluster. This condition is often linked to a Diagnostic Trouble Code (DTC) P066700, indicating a problem with the internal temperature sensor of the transmission control unit.

This TSB provides a comprehensive software update designed to correct the underlying cause of the Audi P066700 fault and prevent the warning light from appearing. It is crucial for affected vehicle owners to understand the symptoms, diagnosis, and the recommended repair process.

Symptoms of the Drive System Fault

The primary symptom reported by owners is the illumination of a "drive system fault warning lamp" in the dash panel insert. While a direct customer complaint might not always be present, the fault is consistently logged in the vehicle's diagnostic system.

Diagnostic Trouble Codes (DTCs)

When this issue occurs, technicians will typically find a specific Diagnostic Trouble Code (DTC) stored in the transmission electronics control unit, also known as the gearbox electronics control unit J217 (diagnostic address 0002). The relevant DTC is:

Code	Description	Symptom Code
P066700	PCM/ECM/TCM Internal Temperature Sensor "A" Range/Performance	20752

This Audi P066700 fault indicates that the powertrain control module (PCM), engine control module (ECM), or transmission control module (TCM) has detected an out-of-range or performance issue with an internal temperature sensor.

Understanding the Problem

The root cause of the Audi P066700 fault is identified as an internal software optimization opportunity within the gearbox electronics control unit J217. This control unit is responsible for managing the vehicle's transmission operations. An inaccurate reading or interpretation from the internal temperature sensor can trigger the 'drive system fault' warning, even if there isn't a physical failure of the sensor itself.

The Solution: Software Update

The recommended repair for this condition is a combined software update for various control units in the vehicle. This update is specifically detailed in a separate Technical Service Bulletin, TSB 2079690, titled "00 Combined software update 03.10.00/c (28.13.01) KD2". This optimized software aims to correct the logic or calibration that leads to the P066700 DTC and the associated warning light.

During the software update procedure, it is standard practice to connect a battery charger to the vehicle. This ensures a stable voltage supply throughout the programming process, preventing potential issues that could arise from voltage drops. The update also includes necessary preliminary and follow-up work, such as bus sleep cycle management and calibration drives, to ensure proper integration and functionality of the new software.

Important Considerations for Owners

Audi emphasizes that this repair should only be carried out if all specified criteria, including model, type, VIN range, engine, gearbox code, part number, and software version, precisely match the TSB's requirements. The bulletin explicitly states:

"Try to reproduce the customer complaint (based on the description/cause of the issue), so that it can be clearly assigned to this TSB. The following repair must only be carried out if all the criteria (model/type, chassis number, engine/motor, gearbox code, PR number(s), part number, software version, code, etc.) apply exactly. Otherwise, this solution will not eliminate the problem and repeat repairs may be necessary. In such a case, the warranty claim may be rejected, and the cost of the parts may be charged back."

This means that attempting this software update for a different or unrelated issue will not resolve the problem and could lead to warranty claims being denied, with the owner potentially incurring the cost of the repair.

Warranty Information and Claim Details

For vehicles still under warranty, this software update is covered. The specific details for processing a warranty claim related to TSB 2080075/2 are as follows:

• Service Number: 3410
• Damage Code: KD02
• Labor Operations:
  • 0151 0010: Software update, including connecting a battery charger. This operation refers to the Service Repair Time (SRT) for associated tasks.
  • 0151 0040: Fixed rate for the software update, encompassing all required preliminary and follow-up work, such as managing the bus sleep cycle, performing calibration drives, and other additional tasks. This operation is typically allocated 130 Technical Units (TU).
  • 0150 9999: In cases where additional attempts are needed due to flash cancellation, an additional lump sum of 50 TU is possible per documented attempt.

If the vehicle is outside of its warranty period, this Technical Service Bulletin is for informational purposes only, and repair costs would likely be the owner's responsibility. All warranty claims must adhere to the Audi Warranty Policies and Procedures Manual.

Next Steps for Owners

If you own a 2025-2026 Audi A5, S5, Q5, or SQ5 and have experienced the 'drive system fault' warning light or suspect an Audi P066700 fault, it is recommended to contact your authorized Audi dealership. They can diagnose your vehicle, confirm the presence of DTC P066700, and perform the necessary software update as outlined in TSB 2080075/2. This will ensure your vehicle's transmission control unit is operating with the latest optimized software.

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Source: NHTSA ID: 11027423