Mercedes-Benz bulletin LI49.20-N-078838
What it saysCheck engine light or Adblue warning with fault codes P206B31, P203B31, or P300494 present in AdBlue (SCR) control unit (N118/5) Complaint The check engine light or AdBlue warning is activated, accompanied by one… NHTSA’s full summary ↓
Mercedes-Benz filed this with NHTSA as a service bulletin dated Mar 23, 2026, received Feb 4, 2025, about the fuel/propulsion system — 4 documents under this number: LI49-20-N-078838 and 3 more. 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.
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What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationCheck engine light or Adblue warning with fault codes P206B31, P203B31, or P300494 present in AdBlue (SCR) control unit (N118/5) Complaint The check engine light or AdBlue warning is activated, accompanied by one or more of the following fault codes related to the AdBlue tank: 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. Cause A. The software for the AdBlue (SCR) control unit (N118/5) is outdated. B. The AdBlue concentration is outside ISO 22241 limits (below 31.8 percent or above 33.2 percent). C. Frozen or partially frozen AdBlue can cause the AdBlue level and concentration functions to report inaccurate values. D. The AdBlue level and concentration sensing functions in the tank are damaged. E. Cold soak and freeze thaw exposure can temporarily create concentration gradients in the tank and lead to sampling dependent readings until fully thawed and mixed. Important Before evaluating any AdBlue concentration result, follow LI49.20-N-080376 to confirm full thaw, perform a mixing drive, and retest. Do not use a single urea percent reading taken from frozen, partially frozen, or not fully mixed AdBlue for a repair or responsibility decision. Remedy A. Software 1. Verify no newer software is available for the AdBlue (SCR) control unit (N118/5). 2. If a software update is available, program the control unit per XENTRY guidance. 3. Only after the system is in proper working condition, complete LI49.20-N-075995 for AdBlue warning reset. Note: If there is no updated software available, print the XENTRY screen indicating this and proceed to section B. B. AdBlue concentration 1. Confirm full thaw and mixing per LI49.20-N-080376, then verify AdBlue concentration. a. Check concentration using the MB refractometer per the MB tool instructions and applicable WIS guidance. b. Use freeze frame data when applicable. 2. If AdBlue concentration remains below 31.8 percent or above 33.2 percent after full thaw, mixing drive, and retest, AdBlue replacement is required. Warranty and responsibility decisions must follow LI49.20-N-080376 warranty handling guidance and standard war-ranty policy. 3. If AdBlue concentration is within specification, proceed to section C. C. Frozen AdBlue or SCR actual values indicate fr
Documents filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| LI49-20-N-078838 | Service bulletin | Mar 23, 2026 | 11030627 | PDF, 476 KB |
| LI49.20-N-078838 | Service bulletin | Mar 18, 2025 | 11016429 | PDF, 476 KB |
| LI49.20-N-078838 | Service bulletin | Feb 4, 2025 | 11014728 | PDF, 362 KB |
| LI49.20-N-078838 | Service bulletin | Feb 4, 2025 | 11013593 | PDF, 365 KB |
What the document itself lists
Part the bulletin names
| Part number | Description | Qty | Find it |
|---|---|---|---|
| A9104702401 | NOX REDUCING AGENT | — | eBay Motors → |
Read by machine from the document NHTSA serves (5 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.
Affiliate disclosure: some links on this page are affiliate links. If you request a quote or buy through them we may earn a commission at no extra cost to you. Nothing on this page changes because of it.
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 10 model years this bulletin names have filed 547 complaints with NHTSA since 2015. 62 of them name Engine, Fuel/Propulsion 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.
SAFETY DEFECT REPORT & RECALL NON-COMPLIANCE: 2018 Mercedes-Benz Sprinter 2500 (VIN: ) This complaint involves an uncorrected emissions system defect that causes a sudden, dangerous engine shutdown and low-speed countdown limp mode on live roadways, combined with manufacturer recall non-compliance by Mercedes-Benz USA and its authorized…
2018 Mercedes-Benz Sprinter · Engine · filed with NHTSA Aug 6, 2026 · ODI 11755370
on 08-03=23, I as driving MB sprinter van on highway Route 84 east toward Connecticut, when I was near Southington exit smoke was coming out of AC vent, I took exit to route 10 and stopped van right after exit on the road, and opened hood, there was active fire near lower left side engine, with help of drivers who stopped behind me, I…
2020 Mercedes-Benz Sprinter · Engine · filed with NHTSA Aug 22, 2023 · ODI 11539986
The ECM harness was wired too close to a sharp metal piece within the engine bay, the clip MBZ uses to secure it was insufficient to hold it back, the thick wiring harness got caught on the metal piece and overtime got cut deeply causing a short with thermal issues spreading to other components, the wiring harness melted together and…
2023 Mercedes-Benz Sprinter · Engine · filed with NHTSA Oct 8, 2026 · ODI 11769942
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 fuel/propulsion system
Source: same model, same component group9 other manufacturer communications filed against the Mercedes-Benz Sprinter under the same component group (fuel/propulsion system), newest first. The eight newest are listed; the rest are on the Mercedes-Benz list.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| LI07_02-N-079573_2_en | Service bulletin | Aug 5, 2026 | Oil Leak at Crankcase Near the High-pressure Fuel Pump OM654 Complaint Visible oil leak at the crankcase near the mounting area of the high‑… |
| LI07.16-N-080732 | Service bulletin | Jun 18, 2026 | Complaint The customer reports that the engine cranks but does not start, or only starts after extended cranking. A check engine light may… |
| LI47_00-N-069565 | Service bulletin | Jun 16, 2026 | Fuel Level Unchanged After Refueling Complaint The customer reports that the fuel gauge shows inaccurate readings or remains unchanged after… |
| LI49.10-N-080528 | Service bulletin | Jun 3, 2026 | OM642 DPF Filter Cracked or Broken Complaint Vehicle will not start or exhibits noisy exhaust. Check Engine Lamp (CEL) is on. Multiple contr… |
| LI49.20-N-078466_4 | Service bulletin | May 8, 2026 | Check engine light with fault code P3005CA in MRD1 (CDI) Complaint The check engine light is on, with a possiblility in a reduction of power… |
| LI4700N069565 | Service bulletin | Apr 29, 2026 | Complaint The customer reports that the fuel gauge shows inaccurate readings or remains unchanged after refueling. Cause A. The Fuel Supply… |
| LI49-20-N-080376 | Service bulletin | Mar 23, 2026 | The check engine light is illuminated, or the AdBlue warning is active, with recorded faults related to AdBlue quality or concentration. Com… |
| LI47.10-N-079010 | Service bulletin | Mar 10, 2025 | Procedure for When Diesel Fuel Tank is Filled with Incorrect Fuel Type Complaint: Procedure for When Diesel Fuel Tank is Filled with Incorre… |
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 LI49.20-N-078838 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-078838 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 LI49.20-N-078838 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.