Mercedes-Benz bulletin LI54.21-P-079510
What it saysComplaint Diverse functional limitations in the vehicle in combination with various warning and fault messages in the instrument cluster display. NHTSA’s full summary ↓
Mercedes-Benz filed this with NHTSA as a service bulletin dated Jul 17, 2025, received Jul 24, 2025, about the electrical system. It names 13 model years (2022–2025). A service bulletin is not a safety recall: it is the manufacturer telling its dealers how to diagnose or repair a condition, and whether the work is paid for depends on the warranty in force. Quoting the number at a service desk can save a diagnosis.
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What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationComplaint Diverse functional limitations in the vehicle in combination with various warning and fault messages in the instrument cluster display. Cause Communication timeouts mean that communication errors may occur in the on-board electrical system, which can result in various fault messages being displayed in the instrument cluster. This could be down to delayed feedback from the drivetrain control unit (N127) (CPC) to other control units networked to the CAN bus. Information: • It may not be possible to attribute any communication errors stored in the control units on the CAN bus to a specific cause. • In rare instances, there may be a brief activation of the yellow warning lamp for engine diagnosis or there may be a sporadic delay with the start enable. • There may not be any specific fault codes present that indicate a specific component. Remedy Do not replace any components!!! 1. Connect charger (see AR54.10-P-1127WT). Note: An adequate voltage from the on-board electrical system battery must be guaranteed for the entire duration of the work procedure. Otherwise the control units could be damaged if an undervoltage occurs. Information: Observe the operating instructions of the charger. Information: Use the charger to ensure an adequate voltage (at least 12.5 V) from the on-board electrical system battery. 2. Connect diagnostic system (see AD00.00-P-2000-06FR). Note: Always use the latest XENTRY Diagnostics software release. Information: Strict compliance with the operation steps in XENTRY Diagnostics is absolutely essential. 3. Select control unit N127 (CPC) via the direct link using XENTRY Diagnosis. Information: To do so, select the following menu items: Control units view → Drive systems → N127 - "Powertrain" control unit (CPC). 4. Update software for control unit N127 (CPC) (see AR54.21-P-0014-01Y). Info: To do so, select the following menu items: Adaptations → Control unit update → Update control unit software. Information: You are then automatically guided through the steps "Update of control unit software" and "SCN coding". Always observe the following operation steps at all times. 5. Disconnect diagnostic device from vehicle (see AD00.00-P-2000-06FR). 6. Disconnect charger from vehicle (see AR54.10-P-1127WT).
Document filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| LI54.21-P-079510 | Service bulletin | Jul 17, 2025 | 11020873 | PDF, 251 KB |
The summary is NHTSA’s abstract of the document, as filed under 49 CFR 579.5. One communication is usually filed as several documents — the bulletin, a dealer notice, an owner letter — and the number on any of them finds this page. A PDF link is shown only once NHTSA’s own server has been seen to serve that document; the rest are checked over the following nights. Quote the number at a service desk; it is what the dealer’s system is keyed on.
Model years it names
Source: as the manufacturer filed themAlso filed against model years this site has no page for: 2024 Mercedes-Benz AMG C63 S E; 2024 Mercedes-Benz AMG S 63 E 4MATIC+.
A vehicle page’s bulletin list shows the newest few communications filed against that model year; the count there is every one.
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What owners reported
Source: NHTSA complaint databaseOwners of the 11 model years this bulletin names have filed 274 complaints with NHTSA since 2015. 102 of them name Electrical System — the same broad component group this bulletin is filed under. NHTSA groups complaints coarsely, so that means the same area of the vehicle, not necessarily the same fault.
The digital instrument cluster and center infotainment display screen went completely black and blank while the vehicle was in motion. This immediate failure blinded the driver to critical safety telemetry, including the current vehicle speed, gear positioning, and active safety warning telltales, creating an immediate, severe crash…
2025 Mercedes-Benz E-Class · Electrical System · filed with NHTSA Jun 23, 2026 · ODI 11746077
On Sunday, XXX at approximately 5:30 PM, I entered the parking lot of a Staples store at , in my 2025 Mercedes Benz AMG GLC 43 SUV. It was daylight and the weather was clear. There was no wind and the temperature was in the low 80s. I drove down a parking aisle and slowed down to make a right turn into an open parking space.
2025 Mercedes-Benz GLC-Class · Electrical System · filed with NHTSA Sep 21, 2026 · ODI 11765946
The electronic system, specifically the battery, failed and it is available for inspection upon request. The persistent battery drain caused the vehicle to become inoperable multiple times, including an incident where I was stranded 200 miles from home with my wife and dog, posing significant safety risks.
2022 Mercedes-Benz C-Class · Electrical System · filed with NHTSA Jun 3, 2024 · ODI 11592228
A complaint is one owner’s account, not a defect finding, and a bulletin is not a recall. Nothing here says this bulletin was issued because of these complaints, or that the repair it describes fixed them. Complaint files on this site begin in 2015.
More bulletins about the electrical system
Source: same model, same component group211 other manufacturer communications filed against these Mercedes-Benz models under the same component group (electrical system), newest first. The eight newest are listed; the rest are on the Mercedes-Benz list.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| LI47.70-P-079912 | Service bulletin | Sep 29, 2026 | Complaint Vehicle will not start after DC charging Warning in the instrument cluster related to High‑voltage on board electrical system The… |
| LI54.30-P-080963 | Service bulletin | Sep 17, 2026 | Complaint Issue after OTA Update IC Odometer Reading blank("_ _ _ _") IC Maintanence data unavailable Cause OTA Update E61.0 Remedy In the I… |
| LI82.60-P-080383 | Service bulletin | Sep 15, 2026 | Complaint Radio station cover art does not refresh when switching stations. The UI continues to show the old station’s artwork instead of up… |
| NCU - 2026090001 | Service campaign | Sep 11, 2026 | Mercedes-Benz AG, the manufacturer of Mercedes-Benz vehicles, has determined that on certain subject vehicles, the control unit software for… |
| LI54.71-P-079104 | Service bulletin | Sep 11, 2026 | Complaint Traffic sign symbol for "Traffic Sign Assist" is blinking in instrument cluster without obvious cause usually with one of the foll… |
| ANN - MY27 XENTRY Comm. | Other | Sep 11, 2026 | A solution for the XENTRY and MY27 167 communication issue is now available through addon 26.6.1.33608. If after ensuring you've installed l… |
| LI54.21-P-080326 | Service bulletin | Sep 9, 2026 | Complaint CEL light on with no drivability concerns. Cause Signal timing error. Remedy 167, 465: SW has been released. Update the FSAM to th… |
| LI82.60-P-079747 | Service bulletin | Sep 4, 2026 | Complaint The Apple Music app is no longer available in the head unit apps menu after updating the software of the… |
Quote the number at the service desk. It is what the dealer’s system is keyed on.
Every manufacturer communication NHTSA holds for Mercedes-Benz, by the number printed on the letter.
Common questions
Source: NHTSA, 49 CFR 579.5Is Mercedes-Benz LI54.21-P-079510 a recall?
No. A service bulletin is a manufacturer communication filed with NHTSA under 49 CFR 579.5; a safety recall carries an NHTSA campaign number (two digits, a letter, six digits) and a federal duty to repair for free. Check the vehicle’s recalls by VIN at nhtsa.gov/recalls, or on its page here.
Is the LI54.21-P-079510 repair free?
Not automatically. A service bulletin describes how to diagnose or repair a condition; who pays depends on the warranty in force, any extension, and the dealer. Quoting the number can save a diagnosis either way. Every Mercedes-Benz warranty extension on file lists the ones Mercedes-Benz has filed.
Which vehicles does LI54.21-P-079510 cover?
The manufacturer filed it against 13 model years: 2025 Mercedes-Benz C-Class, 2024 Mercedes-Benz C-Class, 2023 Mercedes-Benz C-Class, 2022 Mercedes-Benz C-Class, 2025 Mercedes-Benz E-Class, 2025 Mercedes-Benz GLC-Class and more. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.