Buyers and lessees of new Kenworth and Peterbilt trucks with PACCAR’s EPA 2021 MX-13 diesel engine who sought warranty repairs for fuel injector problems may be covered by a proposed class action alleging PACCAR sold the engines with defective fuel injectors it could not fix under its warranty. No class has been certified and there is nothing to file yet.
Allegations Only · No Settlement Yet
This article describes a class action complaint. The statements below are unproven allegations. PACCAR Inc has not been found liable, there is no certified class, and nothing to claim at this time. This page is informational and is not legal advice.
What Is This About?
The case is 10th Gear LLC v. PACCAR Inc., No. 2:23-cv-01933-RSL, filed December 15, 2023 in the U.S. District Court for the Western District of Washington in Seattle and assigned to Judge Robert S. Lasnik. The operative complaint, the Third Amended Class Action Complaint, was filed February 10, 2026 by 31 trucking businesses and individual owners who bought or leased trucks with PACCAR’s EPA 2021 MX-13 diesel engine.The plaintiffs allege that the fuel injectors in the engine fail far more often, and after far less use, than injectors in comparable engines or in earlier versions of the MX-13, and that PACCAR’s warranty repairs never fixed the problem. On October 1, 2026, Judge Lasnik denied PACCAR’s motion to dismiss the complaint, rejecting its argument that the federal Clean Air Act blocks the warranty claim. PACCAR filed its answer and affirmative defenses on October 14, 2026. No class has been certified, and there is no settlement.
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Which Trucks and Owners Are Involved?
The lawsuit concerns tractor-trailer and vocational trucks sold through PACCAR subsidiaries Kenworth Truck Company and Peterbilt Motors Company, beginning with model year 2021, that have the EPA 2021 MX-13 engine made by PACCAR Engine Company. According to the complaint, the engine was one of two engine options in those trucks, alongside a Cummins engine, until 2024, when PACCAR replaced it with the EPA 2024 MX-13.The plaintiffs ask the court to certify a nationwide class of all people and businesses in the United States who bought or leased a new vehicle with the EPA 2021 MX-13 engine and made a claim for repairs under PACCAR’s Limited Warranty Agreement for problems with the vehicle’s fuel injectors. As an alternative, they propose separate classes based on the state where each truck was bought. Owners who never made a warranty claim for injector problems fall outside the proposed class definitions.
What the Truck Owners Allege
The complaint claims that deposits build up on a part inside each injector called the armature plate, causing it to stick. When that happens, according to the plaintiffs, the injector misses the first of the three fuel injections in each combustion cycle, which leads to knocking, heavy vibration and a rough-running engine. They also allege that the trucks’ onboard computers sometimes cut engine power without warning, leaving trucks “virtually undrivable.”The owners claim PACCAR relied on a series of temporary measures rather than a permanent fix: cleaning the injectors, recommending fuel additives, updating fuel-system software and replacing failed injectors with injectors of a similar design. They allege that trucks came back for repair after repair, and that the downtime and the trucks’ falling resale value cost them money. The complaint says some of the trucks sold new for more than $200,000, and that some owners received dealer buyback offers reflecting a 60% drop in value within a year.
The complaint also alleges that PACCAR knew about the problem when it sold the trucks and blamed it on diesel fuel suppliers or weather, even though trucks with other brands of engines fueling at the same stations did not have the same failures. PACCAR has not been found to have done anything wrong.
PACCAR’s Service Bulletins and the Extended Injector Warranty
PACCAR’s basic engine warranty for the MX-13 covers defects in materials and factory workmanship for 24 months, 250,000 miles or 6,250 hours, whichever comes first. A separate emissions warranty, incorporated into the same agreement, runs at least five years or 100,000 miles, with longer terms for trucks registered in California. The warranty makes repair or replacement the only remedy and excludes incidental and consequential damages.According to the court’s February 2025 ruling, PACCAR issued Service Bulletin E290 in March 2022, recommending a cleaning process for deposits that might be clogging the injectors. The bulletin said the procedure was not a permanent fix and that switching fuel sources might reduce deposits if the problem returned. In March 2023, Service Bulletin E300 offered to reimburse customers for up to $830 in fuel additives.
The complaint says PACCAR later extended its warranty on fuel injectors in model year 2021 through 2023 EPA 2021 MX-13 engines to 10 years or 435,000 miles, and that a redesigned injector, called the Pack 2, became available for those trucks in June 2024. The plaintiffs claim it is still unclear whether the Pack 2 is a permanent fix. In its motion to dismiss, PACCAR told the court that the U.S. Environmental Protection Agency and the California Air Resources Board had already addressed the injector issue by requiring the extended warranty coverage.
What the Judge Decided
The only claim left in the case is breach of express warranty. In a February 3, 2025 ruling on an earlier version of the complaint, Judge Lasnik dismissed claims under the Washington Consumer Protection Act, for breach of implied warranty and for fraudulent omission, but allowed the express warranty claim to go forward. That order noted that PACCAR had repeatedly treated the injector problems as covered by its basic engine warranty.PACCAR then argued, in its motion to dismiss the Third Amended Complaint, that the Clean Air Act preempts the warranty claim because fuel injectors are emissions-related parts and federal regulators had already chosen a remedy. The October 1, 2026 order rejected that argument. The court held that the plaintiffs had plausibly alleged a breach of PACCAR’s engine warranty based on how the injectors affect the engine’s operation, a theory that can be decided without asking whether the engines met federal emissions standards. Enforcing that contractual promise, the court found, would not require a judge or jury to second-guess the EPA or CARB, order a recall or impose a different emissions standard.
The court described its ruling as limited. It did not decide whether the injectors are defective, whether the plaintiffs can separately recover under the emissions warranty, or whether particular forms of relief, such as relief that would require a recall or mandate a particular injector design, might still be preempted. The plaintiffs ask for damages, notice to the class about the alleged defect and an order requiring PACCAR to pay for future injector repairs until the Pack 2 design is shown to be a permanent solution.
The court has also ruled on discovery disputes. On October 1, 2026 it granted in part PACCAR’s motion to compel inspections of the plaintiffs’ trucks, and on October 13, 2026 it denied PACCAR’s motion for sanctions over trucks that three plaintiffs had sold or that lenders had repossessed before PACCAR could inspect them.
What Happens Next?
Under the amended scheduling order entered October 15, 2026, the plaintiffs’ motion for class certification is due January 15, 2027, PACCAR’s opposition is due February 12, 2027 and the plaintiffs’ reply is due February 26, 2027. Discovery is set to close June 7, 2027, dispositive motions are due July 6, 2027, and a jury trial is set for October 4, 2027 in Seattle. The schedule has been moved several times since the case was filed.The plaintiffs are represented by Terrell Marshall Law Group PLLC and DLM Law LLC. Until the court certifies a class, approves a settlement or enters a judgment, there is no fund, claim form or deadline for truck owners.
Questions
What is the PACCAR MX-13 class action about?
10th Gear LLC v. PACCAR Inc., filed in December 2023 in federal court in Seattle, claims the fuel injectors in PACCAR’s EPA 2021 MX-13 diesel engine fail early and often, and that PACCAR breached its written warranty because its repairs could not make the engines free from defects. PACCAR is contesting the case and has not been found liable.
Which trucks are involved in the PACCAR MX-13 lawsuit?
The lawsuit covers tractor-trailer and vocational trucks sold under the Kenworth and Peterbilt nameplates, starting with model year 2021, that have the EPA 2021 MX-13 engine. The proposed nationwide class is people and businesses in the United States who bought or leased one new and made a warranty claim for fuel injector problems. Trucks with the later EPA 2024 MX-13 engine or a Cummins engine are not part of the proposed class.
Is there a PACCAR MX-13 settlement or claim form?
There is no settlement, judgment, claim form or deadline. The court has not certified a class; the plaintiffs’ motion for class certification is due January 15, 2027.
What did the judge decide on October 1, 2026?
Judge Robert S. Lasnik denied PACCAR’s motion to dismiss the Third Amended Class Action Complaint. PACCAR argued the federal Clean Air Act preempts the warranty claim because fuel injectors are emissions-related parts. The court held that the plaintiffs had plausibly alleged a breach of PACCAR’s separate engine warranty based on how the injectors affect engine operation, which does not depend on whether the engines met federal emissions standards. The ruling does not decide whether the injectors are defective.
When is the trial in the PACCAR MX-13 case?
An October 15, 2026 scheduling order sets a jury trial for October 4, 2027 before Judge Lasnik in Seattle. Before then, class certification briefing runs from January to February 2027 and discovery is set to close June 7, 2027. Court schedules in this case have changed several times.
Sources
• Order denying motion to dismiss Third Amended Class Action Complaint, ECF No. 164, 10th Gear LLC v. PACCAR Inc., No. 2:23-cv-01933-RSL (W.D. Wash. October 1, 2026)• Third Amended Class Action Complaint, ECF No. 107 (February 10, 2026)
• Order granting in part and denying in part motion to dismiss, ECF No. 40 (February 3, 2025)
• Order denying PACCAR’s motion for sanctions, ECF No. 168 (October 13, 2026)
• Case docket, including the October 15, 2026 amended scheduling order (ECF No. 170)
