2025 Audi A5/Q5/S5 Drive System Fault DTC P071100

Owners of certain 2025 Audi A5, Q5, and S5 models may experience a "drive system fault" warning appearing in the instrument cluster. This issue is detailed in Audi Technical Service Bulletin (TSB) 2079998/2, which outlines a software-based solution for the affected vehicles. The TSB specifically targets vehicles that log Diagnostic Trouble Code (DTC) P071100, indicating a problem with the transmission fluid temperature sensor.

This TSB, released on November 10, 2025, supersedes an earlier bulletin, PSS TSB 2078847. It provides updated instructions for addressing the Audi A5 drive system fault and related diagnostic entries.

Symptoms You Might Notice

If your 2025 Audi A5, S5, or Q5 is affected by this issue, you may observe the following:

• "The drive system fault warning lamp lights up in the dash panel insert." This is the primary owner-facing symptom, indicating a potential problem with the vehicle's powertrain.
• While some owners might report this warning directly, the TSB notes that in other cases, there might be no direct customer complaint, but a relevant fault entry is found during a workshop visit.

Fault Codes / DTCs

Technicians diagnosing the Audi A5 drive system fault will typically find specific Diagnostic Trouble Codes (DTCs) logged in the gearbox electronics control unit J217 (diagnostic address 0002). These codes can be static or intermittent:

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

The presence of P071100, often accompanied by symptom 20756, is a key indicator for this TSB. P270800, with symptom 20859, may also be present.

Diagnosis and Trigger Conditions

Before proceeding with the repair, technicians are advised to try and reproduce the customer complaint to ensure it aligns with the conditions described in TSB 2079998/2. The issue is rooted in optimized software from production, leading to the drive system fault. The TSB also references TSB 2079690, "00 Combined software update 03.10.00/C (28.13.01) KD2," suggesting a broader software update might be relevant or a prerequisite.

Repair Procedure Summary

The core repair for the Audi A5 drive system fault is a software update to the engine control unit. This update aims to resolve the underlying software optimization issue that triggers the fault warnings and DTCs.

Here's a summary of the high-level repair steps:

1. Verify TSB Applicability: Confirm that the vehicle's symptoms and logged fault codes match the conditions described in TSB 2079998/2.
2. Check for Related TSBs: Ensure that TSB 2079690 (00 Combined software update) is not applicable or has already been performed, as it may be related.
3. Perform Software Update: The primary action is to update the engine control unit software. This process typically requires connecting a battery charger to maintain stable voltage throughout the update.
4. Follow-up Work: After the software update, any required preliminary and follow-up work, such as allowing for a bus sleep cycle, performing a calibration drive, and restarting the software if flashing was interrupted, must be completed.

This procedure is designed to optimize the vehicle's software, thereby eliminating the conditions that lead to the "drive system fault" warning and associated DTCs like P071100.

Important Warnings for Owners

Audi has specific warnings regarding software updates and vehicle modifications that owners should be aware of:

• Chip Tuning: If your vehicle's engine control unit has been altered by chip tuning, the software update described in this TSB will render the chip tuning ineffective. More critically, "Damage to the engine control unit resulting from chip tuning cannot be billed to AUDI AG under warranty." Owners are advised to consult with their tuning company before proceeding with any software updates.
• Responsibility for Damage: Audi explicitly states that "neither AUDI AG nor your company can be held responsible for damage caused by the software update or for damage that occurs as the result of not having the update performed." It is crucial to understand these implications and discuss them with your service advisor.

Warranty Information

For vehicles still under warranty, the software update described in TSB 2079998/2 is typically covered. The TSB specifies the following details for warranty claims:

• Claim Type: If the vehicle is outside of any warranty, this Technical Service Bulletin is for informational purposes only.
• Service Number: 3730
• Damage Code: KD02
• Labor Operations:
  • Software update, including connecting battery charger (0151 0010)
  • Fixed rate for software update, including all required preliminary and follow-up work (0151 0040, 130 TU)
• All warranty claims must adhere to the Audi Warranty Policies and Procedures Manual and are subject to review by Audi Warranty.

Owner Action

If your 2025 Audi A5, S5, Q5, Q5 Sportback e-tron, SQ5, or SQ5 Sportback e-tron displays a "drive system fault" warning or you suspect an issue related to DTC P071100, it is recommended to schedule an appointment with an authorized Audi service center. Inform them about the warning message and any diagnostic trouble codes you may have observed. The service center will be able to diagnose the issue and apply the necessary software update as per TSB 2079998/2.

Be prepared to discuss any aftermarket engine modifications, such as chip tuning, as these can affect warranty coverage and the update process. Ensure you understand the implications before authorizing any work.

---

Source: NHTSA ID: 11026272