Saturday, September 30, 2023


Stranded due to DEF head? New developments and a possible workaround

By Russ and Tiña De Maris
If you’re stranded on the road, or afraid to leave home with a Cummins diesel-equipped rig, we have news. Last week we pointed out that Cummins didn’t make those diesel exhaust fluid monitoring (DEF) systems that have fouled up and even stranded so many RVers, but they could help with a solution. Since then we’ve been briefed on a possible workaround that might help some RVers.

We took out the list of corporate officers

First, though, a note on Cummins’ response to your communications to them. Last week we published a list of four Cummins executives (and their email addresses) who you might want to contact. Apparently many of you did, because by Tuesday, we got a pleading request from Cummins to, in their words, “take down or remove any names and emails of our leaders you have posted.” They asked we replace the list with one contact person in their organization. It was not an easy decision, and staff kicked the request around. We finally decided to play ball with Cummins. Our thinking is that it is better for our readers to keep a friendly relationship with Cummins and, in doing so, trust that they will be more forthcoming with information that may be of use.

With that said, be aware that the same Cummins representative promised us that he could, “ensure that the leaders are made aware as appropriate.” The last two words of the statement are open to interpretation. We are hopeful that those of you who are caught up in this unhappy situation will be considered as valuable customers and truly in need of something other than a “We’ll see about it” attitude. Time will tell. Putting the list of executives – and possibly other influential Cummins’ insiders – back on line is not out of the question.

Official corporate-speak

As far as an official position, Cummins was quick to send us a statement in robust “corporate-ese.” The critical statement buried in it reads, “We are also having discussions with our OEMs to consider other ways to mitigate this issue in an effort to best serve our customers, including potentially approaching the regulatory agencies to explore possible solutions.” Excuse us? Sounds a little bit like what we talked about in the last article – get a waiver from the EPA to allow a software patch that stops engine derating when the DEF systems go into glitch mode. RVers (and others) need real solutions today. Our possible workaround is coming – hang on.

“Having discussions,” sadly, often turns into more than a next day, next week, or even next month reality. Here’s our question: How safe do you feel tooling down the interstate in a Cummins-driven motorhome? If your engine derates, your speed dropping down dramatically below “freeway speed,” when you look in the mirror do you fear that oncoming 18-wheeler?

Drive safely!

Here’s a statement Cummins asked us to print, and we do so, in full: “The DEF sensor failure prompts the engine software to follow a derate process mandated by law, which ensures that drivers are notified of the issue and are able to continue operating the vehicle safely for several hours.” Continue operating the vehicle safely? If your rig derates and slows down well below traffic speed, will Cummins hold this “safely” statement up in court when the first of the product liability cases are filed?

While Cummins and other OEMs are “having discussions,” our understanding is that the Environmental Protection Agency is having discussions of its own. We hope to have more to share with you next week. But OEMs should remember that old statement. “If Mama ain’t happy, ain’t nobody happy.” Our suggestion to Cummins and friends is, get yourselves out of “derate” and move on this quickly.

DEF head problems not limited to RVs

Now, as to a possible workaround. RVs and other over-the-road vehicles aren’t the only Cummins-equipped rigs having problems. We got a note from a gent we’ll call the Crane Man. His job is to keep a fleet of rental construction cranes up-and-running. Amongst his fleet, cranes with Cummins QSB 6.7 liter engines. Some of you may have something quite similar under the hood of your tow rig. About four years ago, his company started experiencing DEF head failures. Trouble for crane operators isn’t just a gradual derate. He writes, “Imagine a crane operator holding a 30,000-lb. load, and suddenly with no warning loses all throttle response.” Imagine being the workers down on the ground in the immediate vicinity.

As to when these DEF head problems arise – it’s not something predictable. A DEF head sensor failure can crop up at any time. Crane Man says he’s seen failures pop up on rigs with as little as 137 operating hours on the clock. Like the RV community, the construction equipment community is having the same issue with obtaining parts – they just aren’t out there. Interestingly, Crane Man tells us the manufacturer of the dead-head DEF heads is one Shaw Development. It’s a name familiar to many motorhome owners who’ve been stranded with DEF head issues.

Potential causes of DEF head failure

So what about a possible workaround? Crane Man’s theory on the cause of the DEF head failures is this: Motorhomes are a lot like rental construction cranes. These guys aren’t “daily drivers.” You take your motorhome out on a vacation, come home, park it. It may be weeks or months before you fire the rig up again. Same thing can be true for a rental crane. It could sit in the yard waiting for a call. Meantime, the DEF is sitting in the reservoir, breaking down over time. If poor quality or “late in shelf life” DEF was put in there, the breakdown issue is even worse. You fire up your rig, the potentially unstable DEF triggers a fault code, and the derate process begins.

How does this help you? We’ve heard three theories about DEF head failures. One is what Crane Man describes: Degraded DEF triggers sensor problems. Another theory, which we mentioned last week, is that poor engineering routes hoses right next to the microchips in the DEF head. The heat from the hoses essentially “fries” the chips. And finally, we have read a service bulletin from one manufacturer that suggests the heater hoses for their DEF reservoirs may have been mixed up. The engine coolant used to keep the DEF reservoir warm is being routed the wrong direction, causing a DEF sensor failure.

So here’s the possible workaround

If your DEF head failure is caused by “bad” DEF, or what the system perceives as bad DEF, you MAY learn something from how Crane Man uses a possible workaround. When the dreaded DEF sensor warning appears, his company pulls the DEF tank assembly out of the crane. Next, a tech removes the DEF head and sensor assembly from the tank. The old DEF is dumped, and the tank and sensor are “rinsed completely with distilled water”. The sensor is then put in a clean container and soaked in distilled water for about an hour.

When the time is up, the entire assembly and reservoir tank are reassembled. The reservoir is then refilled with clean, FRESH DEF. In July alone, Crane Man says they’ve done this to two of their rental units, and those sky-lifting moneymakers are back on the job, making money.

And, of course, the fine print

Now, here’s a major caveat on this possible workaround. Crane Man has the advantage of having the official Cummins diagnostic scan tool software (called INSITE). You can pick up your own copy for a cool $1,500. With it, Crane Man can clear the “bad” codes, and force the engine into an exhaust system regeneration. He tells us he “doesn’t have to wait for the code to clear on its own.” Does this mean that folks without access to the scan tool can do the “rinse and clear” trick and get away without resetting the codes? We’re not sure. We’ve asked Crane Man for his opinion, but haven’t received a reply yet.

Is this possible workaround something that might work for you? Clearly worth a try if you’re handy. If you don’t have the scan tool, and can still “do the mechanic-ing,” it could be worth the time to give it a try. We’d love to hear back from anyone who does give it a whirl. What if your skills aren’t up to the job? Then you’d need a cooperative shop willing to try. Of course, if they have the scan tool and software, that’s all the better. We CANNOT tell you that this will work for you – it’s a certified crapshoot. But if you’re stuck 1,500 miles from home with no clear idea of when your parts will come, it’s a “something to think about.”

Even if you’re happy, it may not last

Keep in mind, we know that even RVers who have been in the “happy” position of being able to get a new DEF head have had unhappy endings. New DEF head, and somewhere down the road – maybe not too far – and that dreadful DEF failure code reappears. All we can suggest is this: If you do get your system working, keep the DEF reservoir FILLED with FRESH DEF at all times. If you’re parking the rig for a while between trips consider this: Dumping the tank and refilling with fresh DEF before you head out again.

We can’t say much now, but we can tell you that there are moves underfoot that may offer another possible workaround. This workaround could work for folks whose DEF head issues aren’t necessarily related to bum DEF. We’ll let you know as soon as we can.


Stranded motorhomes. Is Cummins to blame? 

Will a DEF head problem ruin your trip?
Is it safe to run that cheaper Walmart DEF?


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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Mark Hamrick
2 years ago

it is cummings part, whether they make it, or not, they are responsible, everything they get from china or any other country is their fault, the responsibility, the buck stops with them, make it here, make it better,,

1 year ago
Reply to  Mark Hamrick

DEF headers are the OEM’s responsibility. Cummins doesn’t source them, the OEM does

Patricia Briggs
2 years ago

We have a 45’ Tiffin allegro bus with a 450 Cummins that let us down after a Beautiful three week New England vacation ten hours from home. Friday afternoon at 3:30 on I 89 in NH. Had to be towed after drive shaft had to be removed. Tow truck driver on pavement getting drive shaft out while my husband is trying to slow traffic down for two hours. Lives at risk. Towed to a heavy duty truck repair facility (very good one). On Monday (after 3 nights in trucking terminal) they tried flushing system in hot water which was not successful. Told us it would be at least $1000 to try. We needed to be back home for a very important event at our business so we told them to try. (Missed a very important day in our life). Called Cummins and were told not their problem. Asked to bypass and government regulations will not permit and void engine warranty. Only 12k on motor home. Never had any notice that this could happen??? Now had to leave MH ten hours from home because part not available.

2 years ago

3 bolts to remove the DEF injector located just after the DPF (diesel particulate filter) the first big filter after the turbo and clean it off with a wire brush. Also if the SCR (selective catalytic reduction) system isn’t getting hot enough it will cause after treatment and DEF fault code issues. Remove 2 bolts to clean the 7th injector that is located just after the turbo. Both injectors can be cleaned with ease.

2 years ago

This is an electronic problem, not a DEF quality problem, most often. We replace several of these sensors every week due to a failure of the multiplexer (computer chip) that processes the quality level of the DEF, along with the level and temperature of it, and sends that information to the rest of the vehicle.
When those sensors fail, it almost always shows that you have no DEF. The unit derates to force the operator to add DEF.
A simple calibration update to an emergency vehicle calibration will forego the possibility of derate, since emergency vehicles are exempt from this requirement. It will give the warning lights and, if equipped, buzzer. But, you can drive it home…..

Just a friendly tip from someone who specializes in the electronic systems of diesel powered vehicles!

2 years ago

There are so many reason a DEF system can go into D-Rate. I have been certified in Cummins engines and after treatment for 5 years now. In my experience its 50/50 user error and manufacturer and other repair facility’s. If the person writing this would like to email me I would answer any questions I could.

2 years ago
Reply to  Will

A brand new Peterbuilt with factory def broke down and had to be towed 3 times within the first 3000 miles. This was one of my tow trucks. Explain that.

2 years ago

So it’s all ok when us Truck drivers have to spend thousands every year on DEF & DPF related failures, but everyone stands up and takes notice when it’s an RV that’s driven for a few weeks a year.

Paul Smith
2 years ago
Reply to  Jram

Ive been personally lobbying the EPA and Cummins to fix this. I have also had a really hard time getting any trucker attention to this problem even though I see trucks lined up waiting for emissions parts. Ive posted on several trucker forums. If there is a better way to reach truckers please post it here and Ill chase it down as we need everyone to push for change.

2 years ago
Reply to  Paul Smith

Go to any large scale truck stop. Thousands of truckers everyday. Lots of them may tell you more than you want to hear.

2 years ago
Reply to  Jram

I’ve noticed that also.

Roy Davis
2 years ago

Actually it is a prime example of the government screwing things up. It was in 2016 that the rule went into effect requiring the monitoring. One of the alleged justification was that DEF goes bad and people continued to use it which harmed the environment. Neither was proven to be happening in any large extent but that isn’t relevant to bureaucrats. It’s not that it was happening only that it potentially could.

2 years ago

After reading all of your comments, my question is, does or has the Duramax diesel engine been having this problem?

2 years ago
Reply to  Snackmastr

Yes , I own both. DEF is the same on all engines.

2 years ago

I guess we will agree to disagree. I drive a Ford 6.7 diesel and my best friend drives a Ram with the Cummins 6.7. Neither of us have had issues. Buy good DEF and not the cheap stuff at Wally-world and you wIll have less problems. DEF needs to be headed because it will freeze so you need water lines or a heater system like Ford. And when I did have an issue with the DEF heater, my Powerstroke drove 50 miles before it went into a reduced power status. Cheap DEF is a problem

2 years ago
Reply to  Steve

I own a towing company and tow all diesels with def.

2 years ago

This sounds like a long term problem that should have been corrected years ago. Why isn’t there a stabilizer for DEF? It’s not like they give it away! Maybe a class action lawsuit would rattle some cages.

2 years ago
Reply to  TomS

It isn’t just the def. The entire premise is a problem. To many required sensors that go bad. Injection pumps , heating systems that use engine heat, etc.

Nyxlie Machado
2 years ago
Reply to  TomS

I think this is exactly what needs to happen. Cummins should be calling a recall and fixing all these issues. This isnt an isolated issue and everyone knows about it. Something needs to be done right away.

Rolling Coal
2 years ago

There’s several methods to by-pass the DEF system which will totally eliminate the use of DEF and they work well. Each method can be reversed if needed. Yes, I know it’s illegal but the EPA needs to find me first.

1 year ago
Reply to  Rolling Coal

Im interested in more info on methods to bypass the def system incase of emergency.

RV Staff
1 year ago
Reply to  Jerry

Hi, Jerry. Click here and it will take you to several articles on the DEF situation. I hope that helps. Take care. 🙂 –Diane

2 years ago

The SCR header issue is way overblown in my opinion. It’s a very low tech system: float, temp sensor, heating unit, filter, low fluid sensor, and if water heated it has a solenoid to regulate the flow of water. The solenoid can either be replaceable, or part of the header. The solenoid has been the biggest problem, allowing the DEF to overheat when the solenoid fails to close completely. Most other issues are operator error. Contamination from introducing foreign substance ie dirt, diesel fuel, plain water, are some of the major contributors. In a pinch if the water hoses are hot and it’s above 50 degrees the water lines can be pinched off or plugged to keep the DEF from overheating. Engine derating to limp mode is a process that involves an operator driving ” through the warning lights “. The SCR system allows about an hour of non functioning before it even logs the event. Additional warnings or attempts to fool the system will result in eventual limp mode.

2 years ago

There seems to be several theories as to why the DEF system de-rates. It might be time for every owner/operator to file a complaint with the NHTSA folks. After all a stalled (or slow moving MH) is a serious safety issue. If the DEF tanks are improperly wired or the heater lines are wrong these rigs should be recalled for repair!

2 years ago
Reply to  MrDisaster

-Yes!!! I have just recently filed a formal complaint with the NHTSA explaining the serious safety scenarios of these RV DEF failures, asking for them to issue a RECALL. It’s been happening to far too many, and for far too long! These articles in themselves are proof positive of that. -It’s high time for some sort of resolve…hopefully before there is a possible wrongful death lawsuit filed due to a roadside catastrophic incident.

2 years ago
Reply to  Thommy

Engine derating is a driver issue. Proper warnings and time is given to prevent certain issues due to the EATS (Exhaust After Treatment System). By virtue of filling an empty fuel tank with low DEF levels will cause an {bleeped} light to shine if you don’t also top off the DEF tank. Usually it’s a power derating and reduces your torque before a 5 mph total deration.

2 years ago

If the def is sitting in the tank too long and going stale then why are chassis and motorhome manufacturers sticking in larger tanks? Case in point back in 2014 a Cummins 450 ISL on a Spartan/Entegra motorhome was spec’d out with a 10 gal def tank. A few years later the same engine and manufacturer combination has a 15 gal def tank (a 50% increase). The larger the tank the longer potentially stale def is going to be sitting in the tank before it is consumed.

2 years ago
Reply to  Don

The size of DEF tank is proportional to the size of fuel tank installed.

Bob M
2 years ago

Compliments to you for publishing the executives web addresses and those who contacted them. We need to do this in the future to help fellow RVers who have trouble with their RV’s and to improve quality.

Rob Kealey
2 years ago

Cummins is not high on my list, but not for this reason. Our generator failed after less than 50 hours. Just long enough to be out of warranty. $3000 down the drain.

Sink Jaxon
2 years ago

This was a GREAT article, thank you. As far as the Cummins exec’s go, too bad so sad. Stand behind the product you sell!

Last edited 2 years ago by Sink Jaxon
Michael Zehr
2 years ago

I’m so glad that I have an older unit. Mine is a 2000 with a Cummins 5.9 ISB 24 valve. I just spent 3500 having the VP44 injection pump and and a leaking rear main seal replaced. I would rather have an ISC engine but if the time ever comes when the only option left is to get a unit with DEF… I will buy a gas powered unit. I’ve seen and heard of too many units with DEF burning up or having big problems.

Dean McCauley
2 years ago
Reply to  Michael Zehr

Yeah we have a big pull behind TT pulling with a 6.7 Cummins 2008 lots of blown head gaskets with these engines. People who get the tuners and then delete them then unbeknown to them they add in that towing tune therefore adding around another 65 hp the head gaskets are too thin in-between the cylinders, we had it happen 2x’s then put it back on stock tune. On the road for about another month then when we get back home we’re selling the trailer and the truck, if we decide to stay in this RV nightmare then it will be a gas truck and a 4500 lb trailer or even lighter.

2 years ago

Go ahead publish the emails of the top dogs at EPA and let’s blow up their emails to git the same type attention Cummins received!

Might as well rattle their cage while we’re at it!

Thomas D
2 years ago

Would be nice if there was a valve on the tank to dump def. Better yet a guage like you have for fuel. Don’t buy or fill the tank. You could buy a little at every fuel stop. I filled my tank in December,put truk into storage until April and a couple of weeks later bad def signal came on. Then it cleared itself. Too much technology. Trains and planes don’t have exhaust particulate filters nor worry abour def. Just the othe day i read how much fuel the airlines use. In the billions of gallons. Not a drop of def. Lobbyists, nah.

Bob p
2 years ago
Reply to  Thomas D

Airplanes don’t use diesel fuel, plus they and trains are off road vehicles.

2 years ago
Reply to  Bob p

Airplane fuel is gasoline , but jet fuel is diesel. Trains run on diesel fuel. Furthermore jets dump unused fuel before landing. DEF has nothing to do highway use. It is for emissions. It is required on farm tractors also.

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