Mercedes-Benz bulletin LI20.10-P-074508
What it saysComplaint Check engine lamp illuminated. NHTSA’s full summary ↓
Mercedes-Benz filed this with NHTSA as a service bulletin dated Oct 28, 2025, received Aug 4, 2022, about the engine — 2 documents under this number. It names 9 model years (2016–2021). 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 lamp illuminated. Fault code stored P012800-The coolant temperature is below the coolant thermostat specified temperature. Cause Various possible causes Remedy 1- Update HVAC with latest software 2- Perform guided test for fault P012800 and performed repairs per XENTRY diagnosis. - If thermostat requires replacement flush cooling circuit in both directions with 150L of water. MY 2020 GLC350e 253.953 only 3- Update the software of engine control unit N3/10. New version A2749022102 A2749032506. Note- If the guided test passes no repair should be performed. SW update for remaining hybrid models is in development for ME control unit to resolve this fault.
Documents filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| LI20.10-P-074508 | Service bulletin | Oct 28, 2025 | 11024631 | PDF, 83 KB |
| LI20.10-P-074508 | Service bulletin | Jul 13, 2022 | 10217151 | PDF, 83 KB |
What the document itself lists
Parts the bulletin names
| Part number | Description | Qty | Find it |
|---|---|---|---|
| A2749022102 | — | — | |
| A2749032506 | — | — |
Read by machine from the document NHTSA serves (3 pages), 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 9 model years this bulletin names have filed 1,155 complaints with NHTSA since 2015. 364 of them name Engine — 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 2017 Mercedes-Benz C-Class, the 12 owners who gave an odometer reading for Engine reported it at a median of 36,000 miles. That figure is one model year’s, not the whole range this bulletin covers — medians from different model years are not averaged.
Check engine light came on, a day after purchasing from dealer. Mileage at 55k. Check engine light code was p052e71, confirmed from 2 auto repairers. One was Mercedes Benz who quoted me $3900 to repair. In the Mercedes Benz booklet warranty says emission related repairs are covered for 15 years/150k miles for hybrid vehicles
2017 Mercedes-Benz C-Class · Engine · filed with NHTSA Aug 27, 2023 · ODI 11541047
Engine runs rough and activates a flashing engine light. Sounds like the engine is misfiring. On two occasions the engine stalled,(no power steering, brakes...) luckily not in a dangerous situation. No engine codes were visible to a technician when try to diagnose. Car seemed to run fine again after restart
2019 Mercedes-Benz GLC-Class · Engine · filed with NHTSA Aug 21, 2025 · ODI 11682158
At just 30,000 miles — less than half the mileage at which these failures are typically reported — my GLC 43 was found to have active oil leaks in multiple locations: 1. Front engine covers — oil is seeping from both the front cover gasket area and migrating downward along the engine block.
2021 Mercedes-Benz GLC-Class · Engine · filed with NHTSA Jun 8, 2026 · ODI 11742742
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 engine
Source: same model, same component group42 other manufacturer communications filed against these Mercedes-Benz models under the same component group (engine), newest first. The eight newest are listed; the rest are on the Mercedes-Benz list.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| PSL-NCU Return Parts 8/14 | Other | Aug 15, 2026 | Dear Mercedes-Benz USA Dealers, The part numbers listed in the chart below should no longer be installed, and any existing stock must be ret… |
| LI01.20-P-080884 | Service bulletin | Aug 12, 2026 | Complaint Oil leaks found on M176 or M177 engines diagnosed to be from the cylinder head cover area Cause Unknown (under investigation) Reme… |
| LI07.10-P-080384 | Service bulletin | Aug 7, 2026 | Complaint Customer reports Check Engine Light with possible loss of power concern. The Following DTC's are present • P210185 - The throttle… |
| NCU - 2026010004 | Service campaign | Jul 27, 2026 | • Always use the latest XENTRY Diagnosis software release with all available add-ons. • Make sure to follow the operation steps exactly as d… |
| LI20.10-P-072886 | Service bulletin | Jul 24, 2026 | Complaint Check Engine Light ON with DTC P012800 "The Coolant Temperature is Below the Specified Temperature" active and/or stored in the ME… |
| Emissions - 2024100016 | Emissions | Jul 24, 2026 | Mercedes-Benz AG (“MBAG”), the manufacturer of Mercedes-Benz, has determined that on certain MY 2019-2021 C-Class, G-Class, GLC, GT, S-Class… |
| LI01.30-P-072328 | Service bulletin | Mar 27, 2026 | Complaint -Check engine light illuminated. -Engine runs rough. -Poor shifting or jerking when accelerating. -Fault codes stored related to m… |
| LI05.20-P-080329 | Service bulletin | Mar 9, 2026 | Complaint Engine vibrations perceived at low rpm. Fault codes for the camshaft position of the intake camshaft (P001100, P001104, P001200) o… |
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 LI20.10-P-074508 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 LI20.10-P-074508 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 LI20.10-P-074508 cover?
The manufacturer filed it against 9 model years: 2020 Mercedes-Benz C-Class, 2019 Mercedes-Benz C-Class, 2018 Mercedes-Benz C-Class, 2017 Mercedes-Benz C-Class, 2016 Mercedes-Benz C-Class, 2021 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.