Mercedes-Benz bulletin LI54.21-P-078926
What it saysComplaint Check engine light comes on when driving/starting the vehicle. NHTSA’s full summary ↓
Mercedes-Benz filed this with NHTSA as a service bulletin dated Aug 4, 2025, received Mar 28, 2025, about the electrical system — 3 documents under this number. It names 18 model years (2020–2025). 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 Check engine light comes on when driving/starting the vehicle. No drivability concerns. Cause SW conflict of the 48V battery Remedy 1.-Check for SW in the 48V battery. 1. If SW is available, update the 48V battery. 2. Clear all faults and perform a few drive cycles. 3. If no faults return, the vehicle can be released. 2.-If no SW available, perform the following: - Charge the batteries (<5A charging current) - Erase the fault codes - Access the 12V battery contacts - Ignition off and bus sleep for 10 minutes - Disconnect the 12V battery - Wait 10 minutes - Disconnect Connector 3 at the 48V battery - Disconnect Connector 5 at the DCDC converter - Disconnect the 48V and 12V contacts (40/41 and 30/31) at the DCDC converter - Wait for 10 minutes - Reconnect everything back in opposite order and perform the ISU of the DCDC - Conduct a test drive and after check for fault codes U014687 and U044287
Documents filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| LI54.21-P-078926 | Service bulletin | Aug 4, 2025 | 11021897 | PDF, 35 KB |
| LI54.21-P-078926 | Service bulletin | Aug 1, 2025 | 11021149 | PDF, 33 KB |
| LI54.21-P-078926 | Service bulletin | Mar 26, 2025 | 11016046 | PDF, 35 KB |
What the document itself lists
Part the bulletin names
| Part number | Description | Qty | Find it |
|---|---|---|---|
| A0019020424 | — | — |
Read by machine from the document NHTSA serves (1 page), read Sep 30, 2026. A part number is shown only where it matches Mercedes-Benz’s own catalogue shape, an operation only with its code and time, and a description only where the reader got it whole; anything it could not settle is left out, and the PDF is the record. Times are the manufacturer’s warranty allowances, not a quote. Listings and prices on eBay Motors are the seller’s.
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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 themA 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 18 model years this bulletin names have filed 236 complaints with NHTSA since 2015. 95 of them name Engine, 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.
During regular use my 2023, Mercedes Cla 250, had a fault in the instrument display in which the display shut off completely. Only the media display remained on, however the media display is completely useless in this scenario, only the instrument display can show the speed in which the vehicle is traveling and the Rpm range in which the…
2023 Mercedes-Benz CLA-Class · Electrical System · filed with NHTSA Oct 3, 2025 · ODI 11691317
From: Phone: Email: SUBJECT: Vehicle: New Mercedes-Benz GLB 250 VIN: Current Mileage: 39,660 Total Purchase Price: $48,450.00 To Mercedes-Benz USA Corporate Management and Dealership Service Director, This letter serves as a formal written statement regarding an ongoing, unremedied mechanical failure that has now escalated into a severe…
2022 Mercedes-Benz GLB-Class · Engine · filed with NHTSA Aug 25, 2026 · ODI 11759570
As I was driving down road car began to lose power, check engine light came on and car went into limp mode. Car was towed to nearest repair shop where analysis was made. I was advised to take to dealership for repair. Advised that there was a service campaign issued by the manufacturer on GLB class with M260 motors. See attached report.
2021 Mercedes-Benz GLB-Class · Engine · filed with NHTSA Jul 30, 2026 · ODI 11753817
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 group77 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 |
|---|---|---|---|
| LI46.00-P-081006 | Service bulletin | Sep 29, 2026 | Complaint The vehicle pulls to the left or right. Cause In vehicles with Car Package Release "CPR" 2.1.0 or prior, the calibration value for… |
| LI54.71-P-080956 | Service bulletin | Sep 25, 2026 | Complaint 174 with MB. OS 2.1.1 ‑ Driver Assistance System Limited in Instrument Cluster and Does Not Self‑Extinguish. When vehicle is shut… |
| 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… |
| 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… |
| LI54.30-P-080709 | Service bulletin | Sep 5, 2026 | Complaint Display message in the instrument cluster for "Active Brake Assist Inoperative" or "DISTRONIC inoperative". AND Fault code C1100FC… |
| LI27.19-P-080869 | Service bulletin | Aug 29, 2026 | Complaint Temporary no start condition with check engine light and multiple warning messages. When performing a quick test, the following fa… |
| LI54.71-P-080349 | Service bulletin | Aug 26, 2026 | Complaint Frequent rear view camera flap actuations and/or noise associated. NOTE: Rear view camera functions are NOT affected and still per… |
| LI82.90-P-080891 | Service bulletin | Aug 13, 2026 | Complaint • Driving assistance system fault messages are displayed in the driver display. • The switch lighting flashes at night/in the dark… |
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-078926 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-078926 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-078926 cover?
The manufacturer filed it against 18 model years: 2025 Mercedes-Benz CLA-Class, 2024 Mercedes-Benz CLA-Class, 2023 Mercedes-Benz CLA-Class, 2022 Mercedes-Benz CLA-Class, 2021 Mercedes-Benz CLA-Class, 2020 Mercedes-Benz CLA-Class and more. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.