2025 Audi A5/Q5 Charging System Fault U01E400 TSB

Owners of certain 2025 Audi A5, S5, Q5, and SQ5 models may encounter a specific warning message in their instrument cluster related to the charging system. This message, stating "Charging system: fault. AC charging not possible. Please contact workshop", is a known software-related condition. Audi Technical Service Bulletin (TSB) 2078875/1 addresses this concern, clarifying that it typically occurs during the vehicle's start-up phase.

This TSB is important because it advises against unnecessary repairs, ensuring owners and technicians understand the nature of the issue. The appearance of the "Charging system: fault. AC charging not possible" message, even with a combustion engine, is primarily a display anomaly.

Symptoms

Owners may observe the message "Charging system: fault. AC charging not possible. Please contact workshop" displayed in the instrument cluster. This warning can appear despite the vehicle being equipped with a combustion engine, which might seem contradictory. The message is typically sporadic and may not reappear after cycling the ignition off and on again.

Fault Codes / DTCs

When this condition occurs, a specific diagnostic trouble code (DTC) may be logged in the diagnostic address 0019 (Data Bus OBD Interface). The relevant fault code is:

Diagnostic Address	Diagnostic Trouble Code	Fault Symptom	Storage State
0019 - Data Bus OBD Interface	U01E400: Lost Communication with Smart Charging Interface Device "A"	functionality -> faulty	Intermittent / static

This DTC U01E400 indicates a lost communication with the Smart Charging Interface Device "A", often with symptom number 66099.

Diagnosis / Trigger Conditions

The complaint can sometimes be reproduced in the workshop. The TSB specifies that this is a software-related issue that occurs during the vehicle start-up phase. It does not indicate a fundamental problem with the vehicle's charging capabilities or its overall operational safety. The Audi A5 charging fault U01E400 is a transient condition.

Important Warnings

Audi TSB 2078875/1 explicitly states that there is no reason to attempt any further repairs or replace parts for this condition. Unjustified work or replacement parts will be charged back to the dealership, and invoicing under warranty for such actions is not permitted. This is a critical point for both owners and service technicians to prevent unnecessary costs and interventions.

What Owners Should Know

If you experience the "Charging system: fault. AC charging not possible" message or find the DTC U01E400 logged in your 2025 Audi A5, S5, Q5, or SQ5, it's important to understand that this is a known software glitch. The TSB confirms that this issue has no effect on the normal operation of the vehicle. It does not impact the vehicle's driving behavior or its actual ability to charge (for models with hybrid or EV components, though this TSB specifically mentions combustion engines). The sporadic warning message usually resolves itself after a complete ignition cycle.

Therefore, if you encounter this Audi A5 charging fault U01E400, there is no need to be concerned about immediate safety or functionality. No repair is required, and attempting one would be unnecessary.

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Source: NHTSA ID: 11022655