2021-2024 Audi Q7/Q8/SQ7/SQ8/RS Q8 Drive System Fault

Owners of 2021-2024 Audi Q7, Q8, SQ7, SQ8, and RS Q8 vehicles may encounter a critical message in their instrument cluster indicating a problem with the drive system. This concern, identified by Audi Technical Service Bulletin (TSB) 2072000/1, points to a specific wiring harness issue that can lead to limited engine performance.

Symptoms

If your Audi Q7, Q8, SQ7, SQ8, or RS Q8 is affected, you might observe one or both of the following messages displayed in the instrument cluster:

• "Drive system: fault. Limited performance"
• "Maximum engine speed 2000 RPM"

These messages signal that the vehicle's engine performance is being restricted, often as a protective measure when a fault is detected in critical systems like the cooling fans.

Fault Codes / DTCs

Technicians investigating the Audi Q8 drive system fault will likely find one or more of the following Diagnostic Trouble Codes (DTCs) stored in the engine control unit J623 (Address word 0001). These codes can be intermittent or static:

Code	Description	Module
U063200	Lost Communication With Fan 1	Engine Control Unit J623
U063300	Lost Communication With Fan 2	Engine Control Unit J623
P069200	Cooling Fan 1 Control Circuit High	Engine Control Unit J623
P069400	Cooling Fan 2 Control Circuit High	Engine Control Unit J623
P069100	Cooling Fan 1 Control Circuit Low	Engine Control Unit J623
P069300	Cooling Fan 2 Control Circuit Low	Engine Control Unit J623
P048000	Cooling Fan 1 Control Circuit	Engine Control Unit J623
P048100	Cooling Fan 2 Control Circuit	Engine Control Unit J623
P10EFA00	Function limitation due to radiator fan failure	Engine Control Unit J623

Technical Background

The root cause of this Audi Q8 drive system fault is a wiring harness for the radiator fans. This harness may be loose at an attachment point, causing it to chafe against adjacent components. This chafing can damage the wiring, leading to the communication errors and circuit faults indicated by the DTCs.

Production Solution

Audi has implemented an optimized routing for the radiator fan wiring harness in production to prevent this issue in newer vehicles.

Repair Procedure Summary

To address the Audi Q8 drive system fault, technicians will perform the following steps as outlined in TSB 2072000/1:

1. Inspect Wiring Harness: The wiring harness for the radiator fans will be checked in the vicinity of the front right longitudinal member. Technicians will look for any damage in the area typically prone to chafing.
2. Repair Damaged Harness: If damage is found in the affected area, the wiring harness will be repaired using a specialized wiring harness repair set, specifically VAS 1978 B/C.
3. Secure Wiring Harness: After any necessary repairs, the wiring harness must be securely attached at the lower longitudinal member. This involves using the correct attachment point to prevent future chafing.
4. Ensure Clearance: Technicians will verify that there is sufficient clearance around the wiring harness to ensure it does not come into contact with other components.

Important Warnings

When securing the wiring harness, it is crucial to use the correct attachment point. The TSB specifically states: "The wiring harness must be secured at the smaller hole on the right as the clip will not hold permanently in the larger hole on the left."

Required Tools or Parts

For the repair of the radiator fan wiring harness, the following specialized tool is required:

• VAS 1978 B: Wire harness repair set

Warranty Information

This repair is covered under warranty for vehicles up to 48 months or 50,000 miles. For Audi Certified Pre-Owned (CPO) vehicles, the owner's eligibility must be verified. If the vehicle is outside of any applicable warranty, this Technical Service Bulletin serves as informational guidance only, and the repair costs would typically be the owner's responsibility. All warranty claims must adhere to the Audi Warranty Policies and Procedures Manual.

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Source: NHTSA ID: 10245695, TSB 2072000/1