Monday, December 4, 2023


Finally! Possible DEF relief for diesel-powered RVs, trucks

Last year, untold numbers of diesel truck and motorhome owners were stranded when their rig’s DEF (diesel exhaust fluid) systems acted up. Some sat it out for weeks—even months—waiting for unavailable repair parts. Other RVers left their vehicles parked in their driveways because they feared their engine might act up, leaving them stuck beside the road.

The problems stemmed from faulty DEF sensor readings, which caused engine computers to “derate” or severely reduce operating speeds. At the heart of the matter are pollution control regulations from the Environmental Protection Agency. The agency got an earful about these problems, and now the EPA proposes new rules on engine derating. How might you be affected by these rules?

What’s all this about derating?

EPA proposesWhat’s behind derating? A little background will help explain. The EPA set new rules for diesel engines manufactured from 2010 onward. They set air pollution standards, and industry was obliged to figure out how to meet those standards. In the end, the industry’s answer was to use DEF, essentially a mixture of water and urea. Pump a controlled amount of DEF into the exhaust stream; there the DEF is converted to ammonia. The ammonia then breaks down nitrogen oxides, significantly reducing pollution.

With the DEF approach, the EPA was concerned that drivers would be reluctant to spend the money or time to keep putting good quality DEF into their vehicles. Perhaps they might just pour water in their DEF reservoirs. So the agency told manufacturers they had to install DEF monitoring systems. If somebody failed to use DEF or, say, watered it down to the point it wouldn’t do the job, they needed a wrist-slap. In EPA parlance, an “inducement” was required—something that would make using quality DEF more desirable than not.

EPA proposes

The EPA proposed manufacturers “include a derate of the engine’s maximum available engine torque of a sufficient magnitude for the operator to notice decreased operation.” The agency suggested that “at least 25 percent” might be enough to notice. If DEF wasn’t refilled, then a “progression to further degradation” might be in order. The industry took the EPA’s “suggestions” to heart. That “progression of degradation” for many manufacturers meant failing to respond to warnings would leave a driver with a rig running no faster than 5 miles per hour.

More issues

What industry failed to account for, or at least interpret properly, was additional guidance. The EPA told the industry the idea would be that the “inducement” “should not create undue safety concerns, but should make sure vehicle operators are adding DEF when appropriate.” It’s hard to picture how a motorhome traveling a busy interstate highway, derated to 5 miles per hour, could be anywhere close to avoiding “safety concerns.”

EPA proposes

Last year’s debacle of motorhome owners stranded beside roadsides brought up another point, also addressed in the EPA proposal. The vast majority of RVers stuck with derated engines had good quality DEF in their tanks. The problem was faulty DEF sensors, reporting nonexistent problems which triggered the over-enthusiastic derate responses. In most—if not all—cases, the pollution control systems were actually working. DEF was being pumped into the exhaust stream, and nitrogen oxides were being properly reduced. But the technical glitches sidelined RVers who had no control over the problem.

Changes for 2027

The EPA is now working on rules for heavy diesel vehicles that would go into effect in the 2027 model year. Among those rules, the EPA proposes changes to the engine derate issue. Instead of making suggestions, the agency will frame rules for the industry to follow. What’s the bottom line?

powderextreme on

For “high-speed vehicles” like trucks and presumably motorhomes, if operators failed to keep the right quantity and quality of DEF in the tank, here’s what would happen. A dash warning system would tell the driver there was a problem with the DEF system, and a refill was needed. If the warning was ignored, then the vehicle speed would be reduced to no more than 65. After six hours of failing to respond, the speed would drop to 60. At the 12-hour mark, 55 would be the maximum speed. And if the driver took no action, then 50 miles per hour would be the top speed after 60 hours from the first warning.

But what about technical glitches, such as the ones that have caused RVers so much grief? Motoring along with a full tank of high-quality DEF, but derated, nonetheless? The EPA proposes that if the rig is still passing nitrogen oxide standards, as measured by the vehicle’s own sensors, then no derate would happen. The driver would still get a warning, but the engine computer should not kick in speed derates. For do-it-yourselfing RVers, the new rules would also allow them to use a generic scan tool to reset the onboard computer, once they’ve made the necessary repairs. That’s quite a difference. At present, you’d need the specialized service of a shop to get rid of those “check engine” lights related to DEF system problems.

But what about existing rigs?

Should the EPA’s proposals become a rule, all’s well and good for 2027-and-beyond rigs. But what about those who are laboring under DEF sensor problems today? Is there any light at the end of the tunnel? Writes the EPA in the March 28, 2022, Federal Register, it may “be appropriate to allow engine manufacturers to modify earlier year engines to align them with the new regulatory specifications.” The agency is quick to add, “We are not proposing to change the regulation to address this concern. We are seeking comment [from industry and the public] on whether and how manufacturers might use field-fix practices under EPA’s field-fix guidance to modify in-use engines.” They add this could include changing existing “5 mile-per-hour” derates to the 50 mile-per-hour over 60 hours proposal.

It would seem the ball will largely be in the engine manufacturers’ court on this. Will Cummins, et al., be willing to spend a few hours of programmers’ time to rewrite the engine computer control codes? If they were, then will they likewise provide the wherewithal to have that new code plugged into existing engines? Only time will tell. For those who worry their existing rig could be sidelined by false reporting equipment, there’s a solution. Check it out in this article, It’s out there – a DEF sensor workaround.


Russ and Tiña De Maris
Russ and Tiña De Maris
Russ and Tiña went from childhood tent camping to RVing in the 1980s when the ground got too hard. They've been tutored in the ways of RVing (and RV repair) by a series of rigs, from truck campers, to a fifth-wheel, and several travel trailers. In addition to writing scores of articles on RVing topics, they've also taught college classes for folks new to RVing. They authored the book, RV Boondocking Basics.



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Neal Davis (@guest_254013)
2 months ago

Well, I guess I missed this issue of RV Travel when it was current. This is certainly an article of interest to me because our RV is a DP with a Cummins 8.9-liter ISL engine (and a ~15-gallon DEF tank that, happily, is located on the driver-side of the RV). Sorry that the comments got, uhm …, a bit heated now and again.
Thank you for this interesting and well-crafted review of the proposed changes! I found it linked in a discussion on iRV2. Safe travels!

Rigby5 (@guest_252777)
2 months ago

DEF is a really bad idea. DEF does remove all the NOx, but NOx is not at all a threat, since it almost instantly decomposes into harmless components. The biggest source of NOx is jet planes, and no one talks about them using def.
NOx is what you smell when there is lightning. It is natural and normal.
DEF is not, and is very corrosive and harmful.

Steve (@guest_238263)
6 months ago

I have a 2012 duramax with 73000 miles on it and this will make the fourth def reluctant pump unit on it! The def is so corrosive that it eats up the wires and inside of the pump unit! Urea is highly corrosive and now we put ammonia back in the atmosphere! If def is spilled it will damage anything it touches! Safe but very hazardous, yet it really does nothing but cause problems and damage to expensive equipment! EPA and government needs to quit dictating and controlling we the people! To restrict how engines operate is beyond disbelief, clean air in and open air out with no restrictions engines will have a 5/10 longer life! We need to strip this junk off our property and off our equipment! Government needs to back off and stop the EPA, Carbon given off is good for our plant life to survive! Pros and Cons, good vs evil, then the government threatens us that they will destroy us if we don’t conform to their dictatorships ways! This crap needs to stop! Plant trees!

Tony Stekar (@guest_201258)
1 year ago

2019 ram , uses def milage I get is 11 , My 2008 no def got 15 WHERE’S the benefit in adding more stuff to choke my power? All I see is more money taken out of my pocket. Oh and using more fuel that is costing more every year! The first deisel I bought cost me 97 cent a gallon , 15 years later $5.11 why ? Gas didn’t climb as much.

Thomas D (@guest_200500)
1 year ago

I recently lost my chev 2500 hd diesel to a faulty def heater. Keeps it from freezing. It’s currently 87 degrees. Big chance of freezing truck was gone for 5 weeks because of no parts.also cost $1700 in parts and labor. Thanks EPA,now see if you can put the same equipment on the jet planes that fly over my house constantly.
Give a job to government and they will find a way to screw it up. I like the d iesel and consistently get 16/18 miles per gal compared to my v10 ford at 8/10.
Wouldn’t we be better off as a country using fewer liquid gallons than more? Watch tv shows from Europe or England. So many diesels. ( you can hear them)

Mike (@guest_186303)
1 year ago

For perspective on who the REAL polluters are in the world, this article can help:

Al H. (@guest_201771)
1 year ago
Reply to  Mike

A while back I looked into the shipping industry, with all the stuff coming from China, to get some perspective. I can’t vouch for my sources on the internet, but here are the high points that I found:

1) There are about 10,000 cargo ships involved in international trade around the world.
2) They run on “bunker oil,” the worst, most polluting crap they can burn.
3) Because they are in international waters, there’s no particular regulation on emissions.
4) Collectively, those ships burn the equivalent of 75% of the oil output of Saudi Arabia on an annual basis.

If this is even close to accurate, all this stuff about windmills and electric cars is, quite likely, a bill of goods. Just sayin’.

Graeme Thorne (@guest_186005)
1 year ago

Thank you for your information on the def elimination process could someone please tell me where to purchase the necessary equipment and information I have a 2017 Cummins V8 in a 2017 Tiffin Breeze

Michael Scott (@guest_182895)
1 year ago

They should have done this 5 years ago, not 5 years from now.

Richard (@guest_182758)
1 year ago

I’m an ASE master certified technician in heavy truck and automotive. Everything I own is compression ignition. My lawnmower, trucks and my farm tractors. I have never purchased DEF and I absolutely never will. The unreliability alone makes it not worth it, not to mention the fuel economy and power losses. Fuel prices and “emission controls” are killing our economy faster than anything else.

Captain Quirk (@guest_200864)
1 year ago
Reply to  Richard

How are you able to avoid it? As the article says, the engines are designed not to work properly without it.

Whistler's Father (@guest_182576)
1 year ago

Q. What has 152 legs and 12 teeth?
A. The commenters on

BILLY Bob Thronton (@guest_182579)
1 year ago

I just counted mine. THIRTEEN, so there!

Thomas Payne (@guest_182462)
1 year ago

DEF is snake oil. If you don’t buy it your car engine stops working. The snake oil vendor says it’s “illegal” not to buy it. He uses the old “saving the planet” routine.

Bryan (@guest_182440)
1 year ago

I just got an entire system delete for my 17′ Cummins 6.7. EGR delete, 4″ straight pipe, S&B Cold Air Intake, EFILive Race Tuner. Gained about 30-40 HP and comparable torque numbers. Also gained around 7-10 mpg. With diesel in my area roughly $5.60/gal. And 28 gallon tank, your talking minimum 200 more miles per fill up. The weight reduction alone from all the emissions junk would slightly improve fuel mileage.

Timothy (@guest_182454)
1 year ago
Reply to  Bryan

I hope they take it away from you.

Demon (@guest_182456)
1 year ago
Reply to  Timothy

Think about it I catalttic converter decreases horsepower decreases horsepower and overtime worsens the problem by decreasing horsepower you’re also decreasing efficiency and if you’re decreasing efficiency you’re using more gas and if you’re using more gas you’re putting more pollutants in the air and if you’re putting more pollutants in the air then what’s the point of a Cadillac converter, so what it burns a 30% more Combustibles at The cost of efficiency which will make you pump more in the air

Captain Quirk (@guest_200865)
1 year ago
Reply to  Demon

It doesn’t work that way. If it did, why would emission controls exist?

It’s true that emission controls inceease fuel consumption, but what comes out of the tailpipe is much CLEANER.

Rigby5 (@guest_252776)
2 months ago
Reply to  Captain Quirk

@Captain Quirk, what comes out the tail pipe is NOT cleaner.
Catalytic converters produce all sorts of exotic toxins, like cyanates, Sulfites, etc. They just do not check for these exotic toxins. It is not to make the air cleaner, but to make it harder to produce or maintain cars, thus allowing the big 3 to sell more cars. In particular, they use more rigorous testing on foreign imports.

Thomas Payne (@guest_182459)
1 year ago
Reply to  Timothy

He’s just doing what the government told him to do which is to rebel.

BILLY Bob Thronton (@guest_182581)
1 year ago
Reply to  Timothy

Call Bryan up, and talk to him in tree hugger language, he’ll listen, I’m sure of it.

C.j. (@guest_182425)
1 year ago

Aftermarket tuners and delete kits can still be bought but they say there for off road use same tuners and all same price just cut the catalytic converter open an clean it out and weld it back and delete the egr system no problems

Bryan (@guest_182437)
1 year ago
Reply to  C.j.

I just did that to my 2017.

Mikko Rantalainen (@guest_182527)
1 year ago
Reply to  C.j.

Note that some direct injection diesel engines use EGR to control exhaust temperature in addition to reducing NOx emissions. If you delete or block the EGR you have higher probability of cooking your turbo.

Donald Wallen (@guest_182215)
1 year ago

I have a 2015 6.7 and I use very little def fluid. I also installed a tuner to over ride the existing computer. Now I dont have any issues at all for anything. But I do recommend using blue def. Dont try to save a couple of dollars by using the cheap stuff. There is a reason its so cheap. But to replace the exhaust system is about 7000.00. I have friends who own dodge and chevy diesels, and they tend to use more def than I do. It helps to have a light pedal foot too.

Bill vore (@guest_182130)
1 year ago

Delete system if trucking industry would grow a pair pour their $$ in older models maybe they would have engine and truck manufacturers also in the fight

Deb (@guest_182126)
1 year ago

What is the EPA doing about the smoke pollution from the trucks starting on fire during regen??

Jeff Fishel (@guest_182188)
1 year ago
Reply to  Deb

Not just the truck fire I have read stories about brush fires also. The warning states to make sure of your location when doing a Regen. But, you don’t always have a choice in that.

BILLY Bob Thronton (@guest_182097)
1 year ago

The lie began with “good quality DEF” Will you please just stop with such baloney. The EPA is an agency out of control. They, under the unconstitutional and crazy Chevron Doctrine, somehow think they have legislative power, with abilities to regulate and penalize. THEY DON’T. We the people put up with their crazy non-sense. They need to be sued into oblivion and put them back to their original intent, to give advice to the congress. Only the congress has authority under the US Constitution to pass laws. The EPA, has no constitutional authority. You really should take the time to read it. IT’S NOT IN THEIR.

As you will find out in June, when Roe v. Wade is reversed. Why, BECAUSE THE CONSTITUTION DOESN’T SAY IT. It really is that simple.

Tim (@guest_182116)
1 year ago

You’re right. The Constitution doesn’t say anything about an agency protecting the health and well being of the population from known carcinogens.
Did Ben franklin drive his F-350 to Convention Hall in Philly?

BILLY Bob Thronton (@guest_182122)
1 year ago
Reply to  Tim

Why of course not. Ford Motor company, began business on or about 1903, silly man.

Ben Franklin was credited with a major pollution event, when he invented the “Franklin Stove” Oh, the wood smoke pollution, such a travesty, all in the interest of keeping people warm. HOW DARE HE!

Thomas Payne (@guest_182460)
1 year ago
Reply to  Tim

I’ve never met a carcinogen so they’re unknown to me. How many carcinogens have you met? What do they look like? How come you can see them and I can’t?

Dennis Mcilroy (@guest_182194)
1 year ago

Go for you. It is we the people

WCC (@guest_182856)
1 year ago

Congress has the constitutional authority to delegate authority to whomever they please. And how did we go from DEF to Roe v Wade?……sheesh…..

WeThePeople (@guest_183155)
1 year ago
Reply to  WCC

Sorry WCC, the only power Congress can delegate is it’s “advice and consent” power for inferior Officers. Read the Constitution.

Tim (@guest_182077)
1 year ago

So funny.
Everybody complaining about the “Gov’t”.
The real problem here was the manufacturers could have set the engines to derate to any speed. The EPA wanted something to get a driver’s “attention”. The EPA did not tell them to set it at 5 mph.
So why did manufacturers set it to 5 mph?
Why do manufacturers not keep enough stock of replacement parts on hand? This isn’t just about DEF sensors.
I had an ’09 Silverado and a brake sensor went bad. It caused me to have no trailer brakes because the sensor worked with the factory brake controller. I had to wire in an aftermarket brake controller so I could tow.
GM had no, I mean no, nada, nothing, in the whole country for spare sensor. It was six months later the dealer called to say they now had the sensor, bring the truck in.
This was in 2016. No “pandemic excuse”.
I told the dealer forget it, I was getting rid of the truck and I bought a Ram dually.

Steve Browning (@guest_182378)
1 year ago
Reply to  Tim

Agreed. Who would possibly think that 5mph amounted to a 25% decrease? Duh!

Thomas Payne (@guest_182461)
1 year ago
Reply to  Tim

The real problem is somebody threatening to steal your car if you don’t buy his snake oil.

Roger M (@guest_182689)
1 year ago
Reply to  Tim

Disagreement here: The over sensitive DEF system is likely not the answer. Today I have a $330,000 motorhome and two Mercedes Bluetec wagons that have not run on a public street for two months, and no one can identify the issue, no codes no messages No speeds over 45mph.
The plan here is to eliminate high quality diesel engines from our choice selection, by bankrupting the consumer.
Remember back when we decided on 10% of cars in California would be electric, GM and Honda stepped up and later Chrysler, Ford and GM Sued the California EPA? They won the state through in the towel. Soon after GM crushed all the electric cars. Had that not happened we would likely not have this issue today.

A suit by 2 million Americans would be a good start, not against the auto makers but the EPA. How about dropping EPA requirements on vehicles over 9 years old, well after the point most businesses and individuals trade in the previous examples. Or require a system that lasts for 300K miles under warranty like exhaust systems.
I feel we have gone backward 50 years here, as people are scrapping selling or replacing just the Emissions system after 5 years or 110,000 miles.
Diesel engines are not the problem, the fuel and the crap refineries are getting rid of via your tail pipe is the problem. And regardless of what has been said, Government is deeply in bed with big oil, and always has been.
Fuel options are poo pooed and outlawed in favor of the same old fuels with some magic science lowering NOX, big deal. The chemicals not being recorded are the scary part.
I love diesels, I have 6 of them and only one car with a Gas powered V8 running E86 for racing.
I hate to cow under, but I have purchased a pre-DPF truck to replace my current unit. Let me buy an electric car to “Offset my other vehicles, as I doubt a one ton truck will ever pull a 16,000 lb trailer from dawn to dusk.

Chris (@guest_182744)
1 year ago
Reply to  Tim

The EPA is the problem not the manufacturer. The EPA needs to get out of the automobile business.
If they did the price of a new F350 would come back to earth! I bought a new F350 4×4 with a 7.3 turbo diesel in 1993 $17,000 the same truck today $65,000

STEVE (@guest_200951)
1 year ago
Reply to  Chris

The EPA is trying to clean up the air we breathe with its regulations. Otherwise, we’ll all die from breathing polluted air instead of drowning from rising sea levels.

Diesel (@guest_182076)
1 year ago

Runs prewoke engine solves all these issues!

David (@guest_182061)
1 year ago

Why can’t they be like Mahindra? I have a 2018 tractor that doesn’t have to have def fluid in it. So if a tractor company can build a diesel engine that doesn’t have to have it why can’t your auto companies do the same thing?

Tim (@guest_182064)
1 year ago
Reply to  David

If it’s under 75 hp you don’t need def in any diesel

Diesel (@guest_182078)
1 year ago
Reply to  Tim

Now under 25

BILLY Bob Thronton (@guest_182099)
1 year ago
Reply to  Diesel

Correct, it’s engines under 25HP. Why you ask, because the lunitic EPA made up a law, picking some random HP rating. Those clowns had no jurisdiction in doing so.

2nd gen Cummins (@guest_182604)
1 year ago
Reply to  Diesel

My 99 Cummins needs no def and over 500hp, and no emissions from factory. Gonna drive it forever.

Get Freight (@guest_201825)
1 year ago

2004 Power Stroke with the full Bulletproof. Going drive it until the {bleeped} wheels fall off. Would love a new truck but refuse to deal with all this DEF crap.

But it is saving me a crap ton of money. Maintenance and upgrades are cheaper than a new Super Duty.

Gov needs to get out of every facet of our lives.

Mikko Rantalainen (@guest_182528)
1 year ago
Reply to  David

DEF (urea) is required in practice to implement EURO6 emission limits. I would assume a tractor doesn’t need to pass those limits.

Some engine designs can pass EURO5 requirements without extra additives just fine. It’s just the stricter requirements of EURO6 that are next to impossible to implement without additives.

Ed Horton (@guest_202389)
1 year ago

My cousin farms cotton, corn, and soybeans. He says his DEF bill is higher than his diesel bill. Can’t delete because the JD shop will not work on a deleted tractor. So yes, heavy equipment now uses DEF to save the world.

Now if we can get the Chinese and Russia to stop burning raw oil and coal in their factories and power plants…no EPA there. Unlevel playing field.

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