TSB_2078871_2 Service Bulletin/Repair Instructions

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Technical Service Bulletin Transaction No.: 2078871/2

45 Engine warning lamp (MIL) on - DTC U041800 Release date: Jan 30, 2026

Condition

Model(s) Year(s) VIN Range Vehicle Specific Equipment

Ad, S5, Q5, Q5

Sportback, SQ5, and SQ5| 2025-2026

Sportback All Not applicable

AG (FN) 2026

REVISION HISTORY

Revision |Date Purpose

2 - Revised header (Added Model, MY)

1 08/01/2025 | Initial publication

Customer states:
The engine warning lamp is/was on.

Workshop findings:
The customer’s description is plausible. After a bus sleep cycle, the lamp may no longer be on, and the complaint

may not be able to be reproduced in the workshop.
The DTC “U041800 ABS Control Module, implausible signal” is logged with symptom 487509 in diagnostic address

812C.
Technical Background
Signals from the ABS control unit are provided with a delay and trigger the warning lamp if the electrical system

voltage is less than 12V.
Production Solution

Not applicable
Service
This service info aims to provide support during the repair. Please ensure a 12V power supply on the vehicle and

delete the DTC above. The original customer complaint may have been resolved by a bus sleep cycle.
Please re-evaluate the vehicle based on the clear complaints.
The measures on how to correctly provide the signals and revise the warning messages are in development.
Warranty
This service info aims to provide support during work. Billing to this TSB number is not permitted.

Additional Information
All part and service references provided in this TSB (2078871) are subject to change and/or removal. Always check

with your Parts Department and/or ETKA for the latest information and parts bulletins. Please check the Repair

Manual for fasteners, bolts, nuts, and screws that require replacement during the repair.
©2026 Audi of America, Inc. All rights reserved. The information contained in this document is based on the latest

information available at the time of printing and is subject to the copyright and other intellectual property rights of

Audi of America, Inc., its affiliated companies, and its licensors. All rights are reserved to make changes at any time

without notice. No part of this document may be reproduced, stored in a retrieval system, or transmitted in any form

or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may these materials be

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Last update on 2026-03-23 / Affiliate links / Images from Amazon Product Advertising API

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