Mercedes-Benz bulletin LI49-20-N-080376
Mercedes-Benz filed this with NHTSA as a service bulletin dated Mar 23, 2026, received Apr 2, 2026, about the fuel/propulsion system. It names 10 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.
What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationThe check engine light is illuminated, or the AdBlue warning is active, with recorded faults related to AdBlue quality or concentration. Complaint Customer reports an illuminated check engine light and or an AdBlue system warning indicating AdBlue quality out of specification. The vehicle may enter reduced performance mode. One or more of the following fault codes related to the AdBlue tank may be stored: P206B31: Malfunction of the concentration sensor for AdBlue; the signal is absent. P203B31: Malfunction of the AdBlue fill level sensor; the signal is absent. P300494: The quality of the AdBlue is insufficient. Background AdBlue must meet ISO 22241 quality requirements. ISO 22241 urea content limits for AdBlue are 31.8 percent to 33.2 percent by mass. AdBlue begins to crystallize and freeze at approximately 12 degrees F. Freeze-thaw does not degrade the product when uncontaminated, and the bulk concentration returns to normal after complete thaw and mixing. Cause In cold soak conditions and during freeze thaw exposure, the tank contents may not be uniform at the time of sampling or system checks. During freezing and partial thaw, ice formation can temporarily create concentration gradients in the tank. As a result, urea percent readings can vary based on sample location and the state of thaw and mixing, which can produce apparent out of range readings even though the bulk fluid returns to normal after mixing. Remedy Testing Do not use a single urea percent reading taken from frozen, partially frozen, or not fully mixed AdBlue to make a repair or responsibility decision. Confirm full thaw and ensure tank contents are mixed before sampling. 1. Confirm full thaw - Confirm the AdBlue tank and associated components are fully thawed before sampling. - Do not sample slushy or partially frozen fluid. 2. Mix tank contents - Perform a road drive intended to mix the tank contents before sampling. - Idle time alone is not a reliable substitute for mixing. 3. Sample and measure - Take the sample and measure with the MB refractometer per the MB tool instructions. - Record the urea percent value. 4. Interpret the result against ISO 22241 limits - Within specification is 31.8 percent to 33.2 percent urea by mass. 5. Repeat if out of specification - If out of specification, repeat after an additional mixing drive to reduce sampling variation. - If still out of spe
Document filed under this number
| Document | Kind | Dated | NHTSA id |
|---|---|---|---|
| LI49-20-N-080376 | Service bulletin | Mar 23, 2026 | 11030629 |
The summary is NHTSA’s abstract of the document, as filed under 49 CFR 579.5; the full text comes from the manufacturer or a dealer. 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. Quote it 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.
Common questions
Source: NHTSA, 49 CFR 579.5Is Mercedes-Benz LI49-20-N-080376 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 LI49-20-N-080376 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.
Which vehicles does LI49-20-N-080376 cover?
The manufacturer filed it against 10 model years: 2025 Mercedes-Benz Sprinter, 2024 Mercedes-Benz Sprinter, 2023 Mercedes-Benz Sprinter, 2022 Mercedes-Benz Sprinter, 2021 Mercedes-Benz Sprinter, 2020 Mercedes-Benz Sprinter and more. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.