PACCAR bulletin 99-051
What it saysThere is an update to the CARB Base Emissions Warranty Limits table and Manufacturer’s Warranty Coverage section in certain Engine Model Year (EMY) 2025 MX-11 and MX-13 Operator’s Manuals. NHTSA’s full summary ↓
PACCAR filed this with NHTSA as an emissions communication dated May 18, 2026, received Jun 3, 2026, about the engine. It names 8 model years across Kenworth and Peterbilt (2025). 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.
One page for every brand it was filed under. Each brand’s bulletins: Kenworth · Peterbilt.
What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationThere is an update to the CARB Base Emissions Warranty Limits table and Manufacturer’s Warranty Coverage section in certain Engine Model Year (EMY) 2025 MX-11 and MX-13 Operator’s Manuals.
Document filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| 99-051 | Emissions | May 18, 2026 | 11033372 | not found |
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 themKenworth 4 model years
Also filed against: 2025 Kenworth L770; 2025 Kenworth T680; 2025 Kenworth T880; 2025 Kenworth W990.
Peterbilt 4 model years
Also filed against: 2025 Peterbilt 520; 2025 Peterbilt 567; 2025 Peterbilt 579; 2025 Peterbilt 589.
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 group19 other manufacturer communications filed against these PACCAR models under the same component group (engine), newest first. The eight newest are listed; the rest are on the Kenworth list.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| E340 | Emissions | Oct 16, 2026 | KW Certain vehicle model year 2026 Kenworth chassis equipped with EMY2025 PACCAR MX engines require an amended engine label. The engine labe… |
| P001 | Service campaign | Sep 11, 2026 | "KW: The chassis list has been updated to include 1 chassis. The total chassis count is now 53. A link to the PACCAR Powertrain Prognostics… |
| 41-028 | Service campaign | Sep 5, 2026 | The campaign expiration date has been extended from 10/01/2026 to 04/01/2027. |
| P003 | Service campaign | Sep 3, 2026 | "KW: A link to the PACCAR Powertrain Prognostics Webcast has been added in the Links section. PB: The chassis list has been updated to incl… |
| P002 | Service campaign | Sep 3, 2026 | "KW: A link to the PACCAR Powertrain Prognostics Webcast has been added in the Links section. PB: The chassis list has been updated to incl… |
| E316 | Service campaign | Aug 1, 2026 | 235 chassis have been removed from the chassis list and unflagged in PRWS due to expiration of applicable warranty coverage. 5 chassis have… |
| E335 | Emissions | Jul 18, 2026 | Expiration Date Format Update - Certain EPA21 compliant PACCAR MX-13 engines were built with intake valve springs that could fail. This fail… |
| CE033 | Warranty extension | Jun 25, 2026 | "KW & PB 14 fuel injector part numbers (seven for MX-11 and seven for MX-13 engines) have been added to this warranty policy." |
Quote the number at the service desk. It is what the dealer’s system is keyed on.
Every manufacturer communication NHTSA holds for Kenworth and Peterbilt, by the number printed on the letter.
Common questions
Source: NHTSA, 49 CFR 579.5Is PACCAR 99-051 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 99-051 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 99-051 cover?
The manufacturer filed it against 8 model years across 2 brands (Kenworth and Peterbilt): 2025 Kenworth L770, 2025 Kenworth T680, 2025 Kenworth T880, 2025 Kenworth W990, 2025 Peterbilt 520, 2025 Peterbilt 567 and more. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.