2025 Audi A5/Q5 Charging System Fault TSB 2078875/2

Important Warnings for Owners

Audi Technical Service Bulletin (TSB) 2078875/2 explicitly states a critical warning regarding this issue:

• "There is no reason to replace parts or attempt repairs. Unjustified work/replacement parts will be charged back. Invoicing under warranty is not permitted."

This means owners should not seek repairs for the 2025 Audi A5 charging system fault described in this bulletin, as it is not a functional problem and any attempts to fix it will not be covered under warranty.

Symptoms

Owners of affected 2025 Audi A5, S5, Q5, or SQ5 vehicles may observe a specific warning message displayed in the instrument cluster. The verbatim message is: "Charging system: fault. AC charging not possible. Please contact workshop". This message can appear even though the vehicle has a combustion engine and the charging system is otherwise functioning normally.

Fault Codes / DTCs

When this 2025 Audi A5 charging system fault occurs, diagnostic address 0019 (Data Bus OBD Interface) may log several diagnostic trouble codes (DTCs). These codes indicate communication issues or function limitations within the charging system:

Diagnostic Trouble Code	Description	Storage State
U01E400	Lost Communication with Smart Charging Interface Device 'A'	static/intermittent
U011100	Lost Communication With Battery Energy Control Module 'A'	static/intermittent
C1249F5	Function limitation due to Charge management safety functions	static/intermittent

These DTCs are associated with symptom numbers 66099 (for U01E400), 66103 (for U011100), and 66121 (for C1249F5).

Diagnosis / Trigger Conditions

Audi's TSB 2078875/2 clarifies that this issue is a software-related glitch that can occur during the vehicle's start-up phase. The complaint can sometimes be reproduced, but it does not indicate a genuine fault with the charging system. The message typically appears sporadically and often clears after the ignition is completely switched off and on again.

What the TSB Says About the Issue

Audi Technical Service Bulletin 2078875/2 confirms that the appearance of the "Charging system: fault. AC charging not possible" message has no influence on the normal operating behavior of the vehicle. Despite the warning, the vehicle's charging system and overall functionality remain unaffected. This is a known software anomaly, not a mechanical or electrical failure requiring intervention. The TSB explicitly states that there is no technical background or production solution applicable because the issue does not represent a functional defect.

Owner Action

If you own a 2025 Audi A5, S5, Q5, or SQ5 and encounter the "Charging system: fault. AC charging not possible" message, it is important to understand that, according to Audi TSB 2078875/2, no repair is necessary. The message is a benign software glitch. Do not attempt to replace parts or seek repairs for this specific condition, as such actions are not warranted and will not be covered under warranty by Audi. The message usually resolves itself after cycling the ignition off and on.

Revision History

Technical Service Bulletin 2078875/2 has undergone revisions:

• Revision 1: Initial publication on August 1, 2025.
• Revision 2: Revised header, added DTCs, customer codes, and PR number filters. The condition description was also revised.

NHTSA ID: 11025353