By Russ and Tiña De Maris
RVers are in our headlines – getting the credit for some potential solutions to the DEF head problem. If you’ve been following this story, you know that federally mandated DEF (diesel exhaust fluid) monitoring systems have been stranding RVers. It’s a problem with plenty of dynamics, including why the sensors are failing to start with, coupled with a shortage of microchips, and rounding out with recalcitrant industry and government officials. In any event, we have stacks of email from upset RVers who cannot or are afraid to use their rigs because of the issue. But thanks to persistent and innovative RVers, two DEF head alternatives are on the horizon.
Your pressure causes industry and government to act
For weeks we’ve been urging RVers to contact Cummins Inc., the company that has direction over the software that controls the ECMs (engine control modules) that have shut down scores of motorhomes and trucks. When the control module gets a signal that there’s something wrong with the DEF system, it triggers a sequence essentially leading to the shutdown of the engine. In most instances, there’s nothing wrong with the DEF system, it’s just the sensors. RVers have been pleading with Cummins to negotiate with the EPA (Environmental Protection Agency) to allow a software change that would allow affected vehicles to continue to operate if their DEF head signals trouble with the system.
Later, we suggested the campaign for relief include EPA officials, in addition to Cummins. It looks like all your cries of despair may have been heard. Here’s a quote from Cummins: “As we have shared we have been working closely with OEM and industry partners, and the regulatory agencies to find a solution that addresses the widespread shortage of replacement parts related to the DEF sensor failure. We have developed a software calibration for customers who have experienced this failure that will allow customers to continue (or resume) operating their vehicle. Pending the outcome of discussions with regulatory agencies, we expect to begin introducing this calibration across several model years in the next few weeks. The details are being finalized and once ready, customers will receive communication about when and where they can receive the software calibration and next steps once replacement parts become available.”
Devil in the details
The Cummins statement came out Thursday, August 26. It’s a DEF head alternative that may offer relief for many RVers who are broken down with a bum DEF head. But the devil is in the details. For those of you who have not actually “experienced this failure,” but have held back from heading out on the road for fear the “failure” might occur, your relief isn’t so brilliant. If we read the statement literally, if your DEF head hasn’t gone “gunnybag,” you’ll have to wait for it to happen. And if that happens on the road, far from a Cummins authorized shop, well, you can see the problems that could come up.
But hang on, there’s yet another DEF head alternative, and one that may sound better. Once again, we can credit RVers for a solution that industry hasn’t come up with. Mark S. is a smart guy who got into the RV lifestyle when he bought his first rig, a Newmar diesel motorhome. Mark is deeply immersed in all things tech, and shortly after he got his coach, started making a host of modifications to the thing, and now can “voice command” a whole lot of things the rest of us mortals would have to get up and push a button to do.
RVers solve problem that industry couldn’t
Mark and his motorhome found themselves on a two-month trip. In Florida, Mark, like loads of other RVers, got that dreaded DEF check engine light. Happily, a dealer was able to replace his DEF head in short order, but the whole experience left Mark with a bit of anxiety – what if it happened again? He had an 8,000-mile journey planned, and having the DEF head give up the ghost again could leave him in a bad spot. A bit of Internet research soon revealed the scope of the problem of bad DEF heads – and it yielded some other RVers interested in solving the problem – even if industry couldn’t.
Soon Mark and others of interest formed a development group, bent on coming up with a DEF head alternative. It didn’t take them long. With two DEF heads in hand, one that was working, the other that had failed, they were able to determine just what a working DEF head does. Essentially, the DEF head monitors the DEF system. The DEF head communicates the quality (or concentration of urea) of the fluid is within spec. It relates that there is, in fact, DEF in the tank (quantity). This part also reports the temperature of the DEF is in a safe range. As long as the engine control module “hears” from the DEF head that all these parameters are in range, all is good. If not, the ECM (engine control module) is programmed to start the dreaded de-rating process, which leads to an eventual maximum speed of 5 miles per hour.
Tell it what it wants to hear
So what would happen, wondered Mark’s team, if they could construct a device that took the place of the DEF head, and simply told the engine control module “what it wanted to hear”? You might think this would allow folks to cheat and not use DEF at all. But no, other sensors in the exhaust system are also on the lookout for pollutants. If the DEF system were really NOT working – for whatever reason – these other sensors would report to the ECM of the existence of excess pollutants. The ECM would then flash a warning and would eventually shut down the engine.
Could the team build a DEF head alternative this way? Indeed. Writing a bit of computer code and feeding it to an Arduino programmable circuit board, they soon had the answer. Call it a DEF sensor emulator. In practice, the DEF head connector that leads off to the ECM is disconnected, and the emulator is plugged into the wiring. The ECM recognizes the emulator as a “DEF head,” and the board simply feeds data. Initially it tells the ECM that the DEF tank is 75% full, the fluid is 70 degrees, and the urea concentration is 32.5%. As the engine warms up, the emulator tells the ECM that the temperature is increasing, and reports an incremental decrease of the amount of fluid in the DEF tank.
Does it work? Is it legal?
Does it work? Already three motorhomes have been equipped with the new DEF sensor emulator and in test runs have showed no problems. The development team will be installing the system in a motorhome that is already sidelined with a truly bad DEF head, and the rig will then be taken to a service center for replacement with a new DEF head.
Is it legal? The federal government takes a dim view, and applies nasty penalties on those who are caught defeating emission control systems. However, the team tells us that the federal regulations do have allowance for taking an “action” for “the purpose of repair or replacement.” How’s that?
Consider installing this new DEF sensor emulator as an action you take. An action that enables your vehicle to continue to operate until you can repair or replace the bad DEF sensor. The regulation reads, “No action with respect to any device or element of design referred to in paragraph (3) shall be treated as a prohibited act under that paragraph if (i) the action is for the purpose of repair or replacement of the device or element, or is a necessary and temporary procedure to repair or replace any other item and the device or element is replaced upon completion of the procedure, and (ii) such action thereafter results in the proper functioning of the device or element referred to in paragraph (3).”
The emulator doesn’t bypass the actual emission control functions of the DEF system. The DEF system continues to pump fluid into the exhaust stream to reduce nitrogen oxides as the law requires. Those facts make the team feel this is a lawful install. As soon as DEF heads become available, users should get them and remove the DEF sensor emulator.
What’s best for you?
Why not just wait until Cummins and the EPA release what appears to be a software patch? That might be just the ticket for some users. Of course, if your rig is presently non-operational, you’re simply dead-in-the-water until the “fix” comes. The problem is for rigs still running without a DEF warning light. It would seem they might have to keep running until they break. Wherever that might be.
The actual cause of the DEF sensor failures isn’t yet known, although it seems it is somehow heat related. Even with a new DEF head installed, you’re still open to an unwanted breakdown. If you have a DEF sensor emulator in your rig and that warning light goes on, it’s a simple DEF head alternative. Pull over, unplug your DEF head, plug in the emulator, restart your engine a few times, and go. The multiple restarts clear the fault codes from the ECM. Now, go get a new sensor (when available) or go have the dealer “flash” your software.
How can I get one?
If you’re thinking you’d like to have a DEF sensor emulator of you own, you’re asking: “How much?” For a few RVers who are technically adept, you can probably do it yourself for less than $100. You’d need the board and the software code. You’ll also need to build the appropriate wiring to plug into your rig’s wiring harness.
But Mark’s development team has a worry. They fear the skills needed to build and program the system won’t be something the average RVer has at hand. When the group embarked on the project, their thoughts were simply to come up with a DEF head alternative. Finding the solution, then writing code, and putting together the hardware was what lit their lamps. They had no interest in becoming some sort of marketing group. That’s where we sit today. The group is working on this issue, trying to figure out if they can simplify the system enough that the average RVer could put one together, or to provide some other feasible alternative. We’ll be staying in touch with them and keep you up to date.
RVers stranded with bad DEF sensors. What does this mean? Are you affected?
Still stuck with DEF sensor issues? Email Cummins and the EPA
Will a DEF head problem ruin your trip?
Opening image: powder extreme on turbodieselregister.com
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