Mercedes-Benz bulletin LI01.20-P-078446
What it saysComplaint Check engine light on. NHTSA’s full summary ↓
Mercedes-Benz filed this with NHTSA as a service bulletin dated Oct 4, 2024, received Oct 8, 2024, about the electrical system. It names 63 model years (2016–2025). 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 on. One of the below fault codes is current in the engine control module (N3/10). P04DB29, P04DB31, P04DB79 Cause Open circuit or high resistance to crankcase vent line contact Remedy 1. Check the electrical connector for the relevant vent line contact switch noted below. Refer to attached photos of connection locations. 2. Ensure the bolted connection is secure and bolt can be torqued (9Nm). 3. Check continuity from vent line connection to ME control unit. Repair wire if damage is found. • The circuit from ME provides 5V and is pulled to 0V when the ground connection is intact. M260 P04DB31- S88/15 P04DB79- S88/16 M264 P04DB31- S88/15 P04DB79- S88/16 P04DB29- S88/17 M270/M274 P04DB79- S88/5 Note: This repair is not warrantable if the connection was left loose during previous repair/maintenance.
Document filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| LI01.20-P-078446 | Service bulletin | Oct 4, 2024 | 11008712 | PDF, 4,156 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 themand 22 more on this site: 2023 Mercedes-Benz GLB-Class, 2022 Mercedes-Benz GLB-Class, 2021 Mercedes-Benz GLB-Class, 2020 Mercedes-Benz GLB-Class, 2023 Mercedes-Benz GLC-Class, 2022 Mercedes-Benz GLC-Class, 2021 Mercedes-Benz GLC-Class, 2020 Mercedes-Benz GLC-Class, 2019 Mercedes-Benz GLC-Class, 2018 Mercedes-Benz GLC-Class, 2017 Mercedes-Benz GLC-Class, 2016 Mercedes-Benz GLC-Class, 2023 Mercedes-Benz GLE-Class, 2022 Mercedes-Benz GLE-Class, 2021 Mercedes-Benz GLE-Class, 2020 Mercedes-Benz GLE-Class, 2019 Mercedes-Benz GLE-Class, 2020 Mercedes-Benz SLC-Class, 2019 Mercedes-Benz SLC-Class, 2018 Mercedes-Benz SLC-Class, 2017 Mercedes-Benz SLC-Class, 2016 Mercedes-Benz SLK-Class.
Also filed against model years this site has no page for: 2018 Mercedes-Benz A 220.
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 62 model years this bulletin names have filed 3,116 complaints with NHTSA since 2015. 1,364 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.
On the 2016 Mercedes-Benz GLC-Class, the 13 owners who gave an odometer reading for Engine reported it at a median of 27,852 miles. That figure is one model year’s, not the whole range this bulletin covers — medians from different model years are not averaged.
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
In depth: 2017 Mercedes-Benz C-Class engine problems → · 2016 Mercedes-Benz C-Class engine problems →
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 group206 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… |
| 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… |
| 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… |
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 LI01.20-P-078446 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 LI01.20-P-078446 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 LI01.20-P-078446 cover?
The manufacturer filed it against 63 model years: 2022 Mercedes-Benz A-Class, 2021 Mercedes-Benz A-Class, 2020 Mercedes-Benz A-Class, 2019 Mercedes-Benz A-Class, 2023 Mercedes-Benz C-Class, 2022 Mercedes-Benz C-Class and more. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.