2021-2023 Audi A4/A5 Check Engine Light DTC U064100 TSB

Owners of 2021-2023 Audi A4 and A5 models may encounter an illuminated check engine light accompanied by specific diagnostic trouble codes (DTCs). This issue, detailed in Audi Technical Service Bulletin (TSB) 97 24 05 2069123/2, points to communication problems within the fuel tank breather system. The TSB, which supersedes Group 97 number 23-90 dated January 17, 2023, provides a solution for these electrical interference-related faults.

Symptoms

The primary symptom reported by owners is the illumination of the "check engine warning lamp comes on" on the instrument cluster. This warning indicates a fault detected by the vehicle's Engine Control Module (-J623-).

Fault Codes / DTCs

When the check engine light appears, a workshop diagnosis will typically reveal one or more of the following Diagnostic Trouble Codes (DTCs) stored sporadically in the Engine Control Module (-J623-, address word 01):

Code	Description
U064000	Lost Communication with EVAP Fuel Vapor Temperature Sensor Circuit
U064100	Lost Communication with EVAP System Pressure Sensor/Switch Circuit "A"

Diagnosis / Trigger Conditions

The technical background for these fault codes indicates that electromagnetic interference (EMI) can negatively affect the signal from the fuel tank breather system. This interference leads to the Engine Control Module (ECM) registering a loss of communication with the EVAP system sensors, triggering the check engine light. The issue specifically impacts vehicles equipped with the 2.0 ltr. TFSI EA888 engine.

Important Warnings

Audi explicitly states in this TSB: "Replacing the tank pressure sender will not fix the problem." This is a critical piece of information for owners and technicians, as it prevents unnecessary parts replacement and ensures the correct repair is performed to address the underlying EMI issue. For DTCs that are statically stored, this TSB does not apply, and normal diagnosis should be followed.

Repair Procedure Summary

For sporadically stored DTCs U064100 or U064000, the repair involves modifying the wiring harness to mitigate electromagnetic interference. The procedure outlined in TSB 97 24 05 2069123/2 includes:

1. Accessing the Wiring: Technicians begin by removing the plenum chamber covers and releasing the wiring harness securing clips. A seam ripper is then used to carefully expose the wiring harness.
2. Wire Isolation and Modification: Specific yellow/grey and yellow/purple wires within the left and right bundles are isolated. These wires are then cut and untwisted from their original routing.
3. Rerouting and Connection: Using a specialized wire harness repair set (VAS 1978 B), the untwisted yellow/grey wire from the plenum chamber side of the left bundle is connected to the yellow/purple wire on the engine side of the right bundle. Similarly, the remaining yellow/purple wire from the plenum side is connected to the yellow/grey wire on the engine side.
4. Final Steps: After the wire modification is complete, all Diagnostic Trouble Codes (DTCs) are cleared, and the system functionality is rechecked. The modified wiring harness is then wrapped with adhesive tape (N 10729002), and the vehicle is reassembled.

Required Tools or Parts

To perform this repair, technicians will need the following specific tools and parts:

• VAS 1978 B: Wire harness repair set.
• 000979940: Butt connector (2 required).
• N 10729002: Adhesive Tape (2 required).
• Fasteners, Bolts, Nuts, and Screws: As needed per the Repair Manual (refer to ETKA/ELSA).

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 G10 claim type applies, requiring owner verification. If the vehicle is outside of its warranty period, this Technical Service Bulletin serves as informational guidance only. The Service Number for this repair is 9709, with a Damage Code of 0040. All warranty claims must adhere to the Audi Warranty Policies and Procedures Manual, with claims subject to review or audit.

---

Source: NHTSA ID: 10249231