A diesel that keeps throwing emissions faults is more than an inconvenience. When the after-treatment system fails, the truck often drops into a reduced-power mode, refuses to restart after the next key cycle, or sits at the dealer for weeks waiting on a sensor that keeps failing. If the same problem comes back after repeated repair attempts, you may have a lemon law claim. Diesel emissions cases carry wrinkles that gas-engine claims do not, and some of them cross into federal Clean Air Act and consumer-fraud territory.
RockPoint Law P.C. represents diesel owners in New York, New Jersey, Florida, California, and Colorado. Attorney Steven Nassi and the firm work these claims against manufacturers and their warranty administrators.
Start with a free review of your repair records and find out how our diesel emissions lemon law attorneys may be able to help.
Request Your Free Case Review →People lump these together, but they are different legal animals, and the distinction changes who you sue and what you have to prove.
An emissions defect is a component that was supposed to work and does not. The diesel particulate filter clogs and will not regenerate. The selective catalytic reduction system throws a NOx sensor code. The diesel exhaust fluid pump fails and the truck counts down to a no-start. These are warranty problems. Your claim rests on the manufacturer's failure to fix a covered part within a reasonable number of attempts, which is the heart of every state lemon law and the federal Magnuson-Moss Warranty Act.
A defeat device is something else. That term describes software or hardware built to detect an emissions test and run clean only during it, while polluting far more on the road. That was the core of the 2015 Volkswagen scandal. A defeat-device case is a fraud case. It relies on consumer-protection statutes, false-advertising law, and the Clean Air Act rather than a count of repair visits. The vehicle may run fine day to day; the harm is that you bought something the maker misrepresented, and a later government-mandated fix cut your fuel economy or power.
Some fact patterns hit both. A truck can carry an emissions system that was cheated in software and fail repeatedly at the dealer once a recall reflash forces it to run the way it always should have. We look at both angles when we review a file, because the stronger theory is not always obvious at the first meeting.
Not sure which claim fits your truck? Our team can review your situation and explain your options.
Schedule a Free Case Review →State lemon laws share a basic structure even though the numbers differ. The manufacturer gets a reasonable opportunity to fix a defect that substantially impairs the use, value, or safety of the vehicle. If it cannot, the maker owes you a refund or a replacement. Emissions defects fit this framework well, and often better than owners expect.
These are the factors that tend to shape a diesel emissions claim.
"Reasonable opportunity" usually means a set number of tries at the same problem, or a total number of days the vehicle spent out of service. A recurring emissions fault that returns after each dealer visit is the pattern that pushes a truck toward the lemon threshold.
A vehicle capped at 5 mph, or one that will not restart after the DEF countdown hits zero, is arguably a safety defect. That classification lowers the number of repair attempts the law requires in several states, because it puts the driver at risk.
Emissions repairs generate exactly the record a lemon claim runs on. Every dealer visit produces a work order with the fault codes, the parts replaced, and the days in shop. That documentation is often stronger than what a gas-engine complaint leaves behind.
The federal Magnuson-Moss Warranty Act sits alongside your state statute, can reach leased vehicles, and shifts attorney's fees to the manufacturer when you prevail. Protections generally attach during the warranty period, so acting before it lapses keeps your options open.
Because documentation drives these cases, keep your repair orders, fault-code printouts, and purchase or lease paperwork. Keep the vehicle, and do not let the dealer talk you into a trade before you have talked to a lawyer.
Not sure whether your truck qualifies? Our team can review your repair history and give you a straight answer.
Get a Free Case Review →| Factor | What It Means | Example |
|---|---|---|
| Recurring Emissions Defect | The same after-treatment fault keeps returning after the dealer's repair attempts, pointing to a defect that will not stay fixed rather than a one-off code. | A DEF pump replaced twice, yet the no-start countdown comes back |
| Reasonable Repair Attempts or Days Out of Service | State statutes set a number of attempts at the same problem, or a cumulative total of days the truck spent in the shop, before the vehicle is treated as a lemon. | Repeated DPF regen failures spread across several dealer visits |
| Limp Mode or Derate (Safety) | A speed-capped or no-start fault can count as a safety defect, which lowers the number of repair attempts the law requires in several states. | Truck limited to 5 mph after the DEF countdown expires |
| Active Warranty or Emissions Coverage | The defect appears while the vehicle is under the base, powertrain, or separate emissions warranty, which keeps the lemon law clock alive. | An SCR catalyst that fails while still under CARB emissions coverage |
Modern diesels stack several systems to meet EPA and CARB limits, and each one is a common point of failure. None of these is a normal wear item you should expect to replace on a newer truck under warranty. When they recur, that recurrence is the evidence. The claims we see most often involve:
Owners of heavy-duty pickups feel this most. The trucks people buy to tow and haul are the ones that spend the most time in a countdown to reduced speed, because a derate on a work truck means lost jobs and missed hauls. A three-quarter-ton diesel that will not exceed 5 mph after the DEF countdown expires is a truck you cannot use for the exact purpose you bought it.
Our attorneys can review your repair history and assess whether the defect meets the legal threshold for a lemon claim.
Request Your Free Case Review →Diesel emissions litigation has a well-documented history. A short tour helps explain why manufacturers take these claims seriously. These matters do not mean every truck from these lines is defective, and your individual claim does not depend on any of them — a recurring DEF or DPF failure on your specific vehicle stands on its own repair record. We reference these cases to show the pattern, not to promise an outcome.
The 2015 matter is the reference point. Regulators found that certain 2.0-liter and 3.0-liter TDI models ran defeat-device software that passed lab tests while emitting well above the limit on the road, reshaping how the EPA and CARB scrutinize diesel certifications.
The EcoDiesel 3.0-liter V6, used in the Ram 1500 and Jeep Grand Cherokee, drew a reported resolution over emissions-control software after regulators raised similar concerns about how the system behaved on the road.
General Motors faced litigation over the Duramax diesel in the Chevrolet Silverado and GMC Sierra. And in 2024, Cummins resolved allegations tied to emissions defeat devices on Ram 2500 and 3500 trucks in what was widely reported as a record Clean Air Act penalty.
At RockPoint Law we follow a structured framework that keeps a diesel emissions claim moving. The process rewards people who stay organized and act while the warranty is alive. Every case is different, but these are the steps we usually recommend.
We start with a free case review and sort your situation. A covered part that keeps failing points to a warranty-based lemon claim under your state statute or the Magnuson-Moss Warranty Act. Software built to cheat an emissions test points to a fraud theory under consumer-protection law and the Clean Air Act. Getting this right at the start shapes everything after it.
Diesel emissions claims lean hard on a paper trail. Every time the truck goes in for the same fault, get a work order that names the codes, the drop-off date, the date you got it back, and the parts replaced. Save all of them. These documents are how you show the manufacturer had its chances and came up short.
Once the defect has gone through the required repair attempts and still is not fixed, most states have you notify the manufacturer in writing, usually by certified mail, and give it one final chance to repair the vehicle. The notice goes to the manufacturer, not the dealer. Skipping this step can sink an otherwise strong claim.
If the manufacturer runs a qualified informal dispute settlement program, your state may require you to go through it before heading to court. These programs are usually faster and cheaper than a lawsuit, and a lot of claims resolve there.
If the manufacturer still has not fixed the truck or made a fair offer, the next step is arbitration or a lawsuit under your state lemon law or the Magnuson-Moss Warranty Act. We walk through the mechanics on our page about how to file a lemon law claim.
If you are ready to begin, our legal team can guide you through every step.
Start Your Diesel Claim Today →When a diesel emissions claim succeeds, the remedy is usually a refund or a replacement vehicle. The exact result turns on the facts, but the goal is to put the owner back where they should have been.
Possible outcomes include:
The fee-shifting piece matters most to diesel owners. Because the federal statute can make the manufacturer responsible for attorney's fees when you win, many owners can pursue these claims without paying out of pocket. That is why cost should not keep you from finding out where you stand.
Outcomes depend on the specific facts of each case, so no one can promise a particular result.
If you think your truck may qualify, our attorneys can explain the compensation options in your specific case.
Get a Free Consultation →Emissions parts carry their own warranty on top of the standard bumper-to-bumper and powertrain coverage, and diesel owners often do not realize it.
Federal law requires manufacturers to warrant emissions-related components, and California's Air Resources Board mandates longer coverage on the parts it designates as emissions-critical. Major after-treatment components, including the catalyst and, in many cases, the engine control module, can carry extended emissions warranty terms well beyond the base warranty. If you live in California or another state that follows CARB rules, your DPF, SCR catalyst, and related sensors may still be covered even after the standard warranty lapses. Our California lemon law guide covers how these rules play out for owners in CARB states.
This matters for two reasons. A repair the dealer wants to bill you for may in fact be a warranty obligation. And a component still under an emissions warranty that fails again and again keeps your lemon law clock alive. When we review a file, we check every layer of coverage, because manufacturers do not always volunteer that the emissions warranty applies.
Wondering whether your emissions repair should have been covered? We will check every layer of your warranty.
Get a Free Case Review →Every case is different, and the outcomes below reflect the kinds of results our firm's lemon law practice pursues for owners of defective vehicles. They show what a well-documented emissions claim can be worth when it is handled properly.
Recovery of what you paid toward a truck the manufacturer could not fix, less a reasonable allowance for the miles driven before the first repair.
A comparable vehicle in place of a diesel that kept derating, failing DEF or DPF repairs, or dropping into limp mode.
Resolutions where the Magnuson-Moss Warranty Act made the manufacturer responsible for attorney's fees and costs, so the owner kept more of the recovery.
Outcomes depend on the specific facts of each matter. Prior results do not guarantee or predict a similar outcome in any future matter. See more RockPoint Law settlements →
The right attorney can change the outcome of a diesel emissions claim. At RockPoint Law we focus on helping consumers protect their rights and resolve disputes with major manufacturers and their warranty administrators.
RockPoint Law is led by Steven P. Nassi, Founder & Managing Partner, a seasoned attorney with more than 25 years of litigation experience in state and federal courts. Steven concentrates on consumer protection law, particularly lemon law and breach-of-warranty claims, and he reviews this diesel emissions guidance for accuracy.
Lemon law is not a side practice here. It is the whole practice, focused on drivers dealing with defective vehicles.
DPF, DEF, SCR, EGR, and NOx faults are their own world. We know how these systems fail and how a derate or no-start reads under the statute.
We work both your state statute and the federal warranty act, including the emissions-warranty layers manufacturers do not always volunteer.
Straight updates at every stage of your case. No silent weeks, no surprises.
Qualifying cases are handled on contingency, and many proceed with the manufacturer responsible for fees when the owner prevails.
We know how much a truck stuck in derate disrupts a working week. Our job is to give you reliable guidance and pursue a result that lets you move on.
| Without a Lemon Law Attorney | With RockPoint Law |
|---|---|
| Communicating directly with the manufacturer and its warranty administrator | Attorneys handle all communications and negotiations |
| Uncertainty about whether it is an emissions defect or a defeat-device claim | A clear evaluation of whether the lemon law, Magnuson-Moss, or a broader emissions theory fits your facts |
| Accepting a repair bill that may be a covered emissions-warranty obligation | Every layer of coverage checked, including CARB and EPA emissions warranties |
| Risk of missing written notice or trading the truck before you should | Notice, deadlines, and the vehicle preserved to protect the claim |
RockPoint Law reviews diesel emissions lemon law claims in New York, New Jersey, Florida, California, and Colorado. We help owners resolve disputes with major manufacturers, wherever the dealership and the defect happen to be.
We regularly assist diesel owners in:
Because each state runs its lemon law a little differently, and because California's CARB rules add their own emissions-warranty layer, we tailor the approach to where you bought and drive the truck. Our goal is reliable legal help that protects your rights and gets to a real solution.
Owners often weaken their own case with small mistakes early on. Knowing what to avoid protects your rights and improves your odds of a successful claim.
Common mistakes include:
Acting early makes a real difference. When owners keep clear records and get legal guidance while the truck is still in the driveway, they put themselves in a much stronger position.
If you are unsure about the best next step, our attorneys can help you evaluate your situation and build a strategy.
Talk to a Lemon Law Lawyer →Reach out once you see a pattern rather than a single visit. You do not need to diagnose the engineering yourself. You need to preserve the record and get an honest read on whether your state's statute, Magnuson-Moss, or a broader emissions theory fits your facts.
Good signals that it is time, and what to bring:
These steps create a clear record of the failures, the days in shop, and the parts replaced, and they show the manufacturer had a fair chance to fix the problem.
If you are dealing with a defective diesel, our team at RockPoint Law is ready to help you understand your options.
Request a Free Case Review →Our attorneys field these questions from diesel owners all the time. Here are the ones we hear most and what owners should know.
Reviewed by Steven Nassi, Founder & Managing Partner, RockPoint Law P.C. Last reviewed July 2026.
The information provided on this page is for general informational purposes only and does not constitute legal advice. Reading this content or contacting RockPoint Law P.C. does not create an attorney-client relationship. Diesel emissions and lemon law cases vary depending on the facts of each situation and the applicable state and federal law, including the Magnuson-Moss Warranty Act and the Clean Air Act. Prior results do not guarantee or predict a similar outcome in any future matter. For advice about your specific legal matter, contact RockPoint Law P.C. to schedule a consultation with a qualified attorney.
