2021-2022 Audi HUD Inoperative, Battery Drain TSB 2064692/1

Symptoms

Owners of affected 2021-2022 Audi models may experience several issues related to the head-up display (HUD) and vehicle electrical system. The primary symptom is that the head-up display (HUD) does not turn on. This can be accompanied by a message on the MIB display stating, "The selected system is currently unavailable". Additionally, vehicles might suffer from a drained 12V battery, indicating a persistent electrical draw.

Fault Codes / DTCs

When diagnosing the Audi HUD inoperative condition, technicians may find a specific Diagnostic Trouble Code (DTC) stored in the information electronics control module, J794 (address word 005F). This DTC points to a communication issue with the HUD.

Code	Description	Module
U131C00	Head-up display control module on fiber optic MOST data bus no communication	J794

Diagnosis and Trigger Conditions

Workshop findings indicate that the root cause of the Audi HUD inoperative issue and subsequent battery drain is often the HUD preventing the vehicle's databus system from entering sleep mode. This is identified by running the test plan "0019 – Read data bus sleep inhibitor". If this test plan confirms the HUD as a sleep inhibitor and the DTC U131C00 is stored with high frequency, the Technical Service Bulletin (TSB) applies.

Interim Repair Procedure Summary

As of the TSB date, the issue is still under investigation, and the provided solution is an interim measure. The repair involves resetting the head-up display by temporarily removing its power supply for approximately five minutes. This is achieved by removing a specific fuse depending on the vehicle model:

• For Audi Q7, Q8, Audi e-tron quattro, and Audi e-tron sportback models: Remove fuse SF4.
• For Audi A6 and A7 models: Remove fuse SG4.

This procedure aims to temporarily resolve the Audi HUD inoperative state and mitigate the battery drain until a permanent software update or fix is developed. Audi states that the TSB will be updated as soon as further information is known.

Important Warnings

Owners and technicians should be aware of a critical instruction from Audi regarding this issue:

• Do not replace any components. This TSB explicitly states that replacing components will not resolve the underlying problem, as the issue is still under investigation.

Warranty Information

This Technical Service Bulletin outlines specific warranty claim details for the interim repair:

• Claim Type: The repair is covered for vehicles up to 48 months or 50,000 miles. For Certified Pre-Owned (CPO) vehicles, it falls under claim type G10, requiring owner verification.
• Out-of-Warranty: If the vehicle is outside of its warranty period, this TSB serves as informational guidance only.
• Service Number: 9091
• Damage Code: 0040
• Labor Operations: The labor operation for repairing the control unit for the head-up display is 9091 4199, with an allowance of 20 Technical Units (TU).
• Diagnostic Time: Diagnostic time (GFF) is 0150 0000, with a maximum allowance of 30 TU, as stated on the diagnostic protocol.
• Road Test: No allowance (0 TU) is provided for road tests before or after the service procedure.
• Claim Comment: Claims should reference TSB #2064692/1.

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Source: NHTSA ID: 10202217