Paccar bulletin E321
What it saysCertain chassis equipped with a PACCAR MX-11 EMY18 engine are eligible to receive software improvements to increase vehicle uptime and functionality of emissions fault detection. NHTSA’s full summary ↓
Paccar filed this with NHTSA as an emissions communication dated Mar 1, 2025, received Mar 4, 2025, about the engine — 2 documents under this number. It names 3 model years (2018–2020). An emissions communication is not a safety recall — there is no NHTSA campaign number and no federal requirement — but it is usually work the manufacturer pays for on the vehicles it names; the dealer checks the VIN against the manufacturer’s list.
What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationWhat it applies to, as the document itself states it — the build window in the manufacturer’s own words, read by machine from the PDF NHTSA serves. The build date is on the certification label in the driver’s door jamb; the dealer settles a borderline vehicle by its VIN.
Certain chassis equipped with a PACCAR MX-11 EMY18 engine are eligible to receive software improvements to increase vehicle uptime and functionality of emissions fault detection. The software updates will allow Forward NOx sensor deviations to be detected prior to OBD Emission Limit (OBDEL) exceedance.
Documents filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| E321 | Emissions | Mar 1, 2025 | 11014762 | PDF, 467 KB |
| E321 | Emissions | Mar 1, 2025 | 11014758 | PDF, 179 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 themAlso filed against: 2018 Paccar MX-11; 2019 Paccar MX-11; 2020 Paccar MX-11.
None of these model years has a page on this site (it covers EPA-certified cars, trucks and SUVs from 2016), so the bulletin is listed here on its own.
More bulletins about the engine
Source: same model, same component group2 other manufacturer communications filed against the Paccar MX-11 under the same component group (engine), newest first.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| E273 | Emissions | Aug 22, 2025 | Fix As Fail Part number 2200138 DPF Pressure Sensor has been added to the parts table for the following PACCAR MX engines: •EMY2021 MX13-1… |
| E327 | Emissions | Feb 27, 2025 | "PSB E327: PACCAR MX-11 and MX-13 OBD Software Update Vehicles equipped with PACCAR MX engines with Engine Software Version NA202 or NA206 m… |
Quote the number at the service desk. It is what the dealer’s system is keyed on.
Every manufacturer communication NHTSA holds for Paccar, by the number printed on the letter.
Common questions
Source: NHTSA, 49 CFR 579.5Is Paccar E321 a recall?
No. A emissions communication 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.
Is the E321 repair free?
A emissions communication is usually paid by the manufacturer on the vehicles it names, within the terms and time limit the document sets; the dealer checks the VIN against the manufacturer’s list.
Which vehicles does E321 cover?
The manufacturer filed it against 3 model years: 2018 Paccar MX-11, 2019 Paccar MX-11, 2020 Paccar MX-11. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone. The document itself sets the build window: built 19 May 2017 – 18 Jan 2019 — the build date is on the certification label in the driver’s door jamb.