2025 Audi A5/Q5 Charging System Fault U01E400 TSB

Owners of certain 2025 Audi A5, S5, Q5, and SQ5 models may occasionally see a message in their instrument cluster stating, "Charging system: fault! AC charging not possible. Please contact workshop." This warning is often accompanied by a logged diagnostic trouble code (DTC) U01E400. Audi Technical Service Bulletin (TSB) 2078875/1 has been released to address this specific concern, clarifying the nature of the issue and advising against unnecessary repairs. If you encounter the 2025 Audi A5 charging system fault U01E400, understanding this bulletin is key.

Symptoms

Owners may observe the following symptom:

• An instrument cluster message displaying: "Charging system: fault! AC charging not possible. Please contact workshop."

This message can appear even though the vehicle is equipped with a combustion engine and does not rely solely on AC charging. The TSB notes that this complaint can sometimes be reproduced, but it is typically a sporadic occurrence.

Fault Codes / DTCs

When this condition occurs, the following diagnostic trouble code may be logged in diagnostic address 0019 (Data Bus OBD Interface):

Diagnostic Address	Diagnostic Trouble Code	Fault Symptom	Storage State
0019	U01E400	Lost Communication with Smart Charging Interface Device "A"	Intermittent
0019	U01E400	Lost Communication with Smart Charging Interface Device "A"	Static

The TSB also identifies the internal fault label for U01E400 as "Control unit for charging communication, lost communication" with symptom number 66099.

Important Warnings for Owners and Technicians

Audi's TSB 2078875/1 provides crucial information regarding this specific issue, emphasizing that no repair is necessary. Owners should be aware of the following:

• "There is no reason to replace parts or attempt repairs."
• "Unjustified work/replacement parts will be charged back. Invoicing under warranty is not permitted."
• "The appearance of the message in the instrument cluster has no influence on the normal operating behavior of the vehicle."
• "The sporadic warning message usually doesn't appear after completely switching the ignition off and on again."

These statements are critical as they prevent unnecessary diagnostic time and part replacements that would not resolve the underlying condition.

Understanding the Issue

Audi identifies this as a software-related issue that occurs during the vehicle's start-up phase. It is described as a rare occurrence that causes the warning message to be displayed. Despite the warning, the TSB explicitly states that this condition has no effect on the normal operation of the vehicle. The message is typically sporadic and often resolves itself after the ignition is cycled off and on again. This means that while you might see the 2025 Audi A5 charging system fault U01E400, it does not impair your vehicle's functionality.

What Owners Should Do

Given that Audi Technical Service Bulletin 2078875/1 clearly states that this is a benign software glitch with no impact on vehicle operation and no need for repairs, owners should not be concerned if they see the "Charging system: fault! AC charging not possible" message or if DTC U01E400 is logged. There is no action required on your part, and you should not authorize any diagnostic or repair work related to this specific warning, as it will not resolve the issue and may not be covered under warranty.

If you encounter this message, simply cycling the ignition off and on may cause it to disappear. If you have concerns about other charging system issues not covered by this specific TSB, consult with an authorized Audi service center.

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Source: NHTSA ID: 11022685, Transaction No. 2078875/1