DEF Head Problems, Sensors, and Failure (What Is a DEF Head?)
It is thought of as one way to lower emissions. When the DEF system breaks down it does its job. No one can drive anywhere thus lowering emissions. Repair shops may not be that helpful as they get booked up quickly.
The DEF head is the part that does all the monitoring of the DEF system. When it detects a problem, it sends a message to your ECM. If the problem is serious enough, the ECM can start the shut down process. When the head goes bad, you have a lot of trouble.
To learn more about this exhaust system just continue to read our article. It has the information you want to know about. If you own an RV or truck with a diesel motor, take a few minutes to see if this important content helps you solve your problem.
What is a DEF Head?
This is the part that watches over your DEF exhaust system. When there is a problem, the head detects it and sends the proper message to your ECM. Once your ECM gets the message different warning rights are triggered and it is possible that it will send your engine into de-rate mode.
There may be different companies making this system and the design for their heads may be different. KUS makes 3 different styles of this part:
1. the Bayonet Mount- this is supposed to be a versatile design and needs an 0-ring to seal it.
2. the Rubber Head Mount- is very easy to install and is designed for those engine compartments that have little room.
3. the Flange and Bolt Mount- also easy to install and needs bolts and screws to be mounted correctly.
You may have a DEF system made by Tiffin and repairing it is not so easy. It is time-consuming as the body panel needs to be removed. There are also 4 hoses that have to be disconnected before you can remove the tank.
DEF Head Problems
One of the more common problems that can arise is a sensor failure. Sensors are the life-blood of any system and when they fail, your EM gets bad information and responds accordingly.
These sensors can come bad from the manufacturer. You never know which option is the cause of the problem. Then the head can be faulty or go bad and also send out false information.
It is hard to tell if it is a real problem or a faulty one when you get a bad check engine light message. If you are caught out in the middle of nowhere, it will be a tough decision to make. Do you stop or keep on going?
The biggest problem is getting replacement parts. Dealers and repair shops say they do not know when they will get them and for some owners, they are waiting months.
Some companies are blaming the supply chain for this lack but it is hard to tell if that is a legitimate reason or just a handy excuse. It is hard to circumvent the DEF system.
All the engine parts seemed to be designed in such a way that f they are altered, the transmission won’t shift or the engine shuts down anyways.
DEF Head Failure
There are different sources for this problem. We will leave out the possibility of factory fault in this section. It happens but it may not be a common problem. If it does, you have a path to get it replaced.
One source would be that the DEF fluid has sat for too long. When this happens it breaks down. As you start your engine, you are sending bad fluid through the system, that bad fluid triggers the sensor which sends the error code which starts the de-rate process.
It is not always the fault of the system or the manufacturer. The second source would be the fault of the company. Their engineers routed hoses to go right by hose microchips in the DEF system.
Because of that design, the heat from the hoses fries the chips and ruins your system. A third source would also be a bad design. The coolant hoses were installed in the wrong way.
This sent the coolant off in the wrong direction and the system does not get cooled down. The heat fries some more parts causing the problem once again.
How do You Bypass The DEF System?
This is very hard to do as one owner disconnected his speedometer. Once he did that, the transmission would shift. If you are trying to solve this problem on your own the solution may cause you more problems.
Here is a link to a news article that describes a legitimate solution that does not create those extra problems. The gist of the article is this:
“Mark found a way to use a low-cost Arduino micro computer to Replace the DEF head and satisfy the engine computer till the faulty sensor can be replaced. This is a small box you can put in a storage bin till needed and when (not if)the flakey sensor flakes.. plug it in and go to your nearest Cummings dealer for a new head. No need for a thousand mile tow bill.”
Sending a different message, one the ECM wants to hear, is the best solution we have seen so far.
Why Are DEF Sensors Failing?
One reason is that they are defective from the manufacturer. The reason for that situation is anyone’s guess. They could have been sent defective materials or someone screwed up when placing those materials together and so on.
Another reason would be the quality of the DEF fluid you run through the system. If the fluid breaks down that corruption can easily trigger a sensor and make it seem like it is failing.
Or the sensors just fail. It has been said that between 2017 and 2018 the DEF sensors just failed at 20,000 miles. It was like clockwork and that suggests faulty sensors from the manufacturer.
Also, the chips could be fried and they say there are no replacement chips at this time. That seems to be the biggest issue right now and another website has been posting the names of Cummins execs and EPA officials along with their contact information o you can complain.
To get that information, click here. This is a complex problem it sees but no one wants to solve it except the person who was the subject of that news article we linked to.
Can You Clean a DEF Quality Sensor?
This will depend on the design of the sensor. For a Kenworth truck, the sensor is about 18 inches to 2 feet long and that may not be the size of your sensor. You can clean this one unless there is a short in the sensor.
If your sensor or sensors can come off, look at how they are constructed. If they are water tight, then you can use hot water and Windex to soak the sensor. Soak for 30 minutes, then rinse off.
If there is a lot of build-up, you may be able to remove the mirror and then spry some Windex on the area and wipe it off. Of course, you need to make sure it is completely dry before reinstalling the sensor.
Your dealer may have more tips as cleaning needs to be done according to the design of the sensor. Or a good mechanic should be able to tell you how t get this task done.
DEF Sensor Simulator
Basically, this is one of the solutions you can build yourself and protect your vehicle from a bad sensor. When installed, the simulator can remove the de-rate status and let you drive normally to a repair station. Or until a permanent replacement can be found.
Of course, this simulator only works when there are no other problems involved with the de-rate in your engine. Keep in mind that it is illegal to alter emission control systems and keep them from doing their job.
The simulator does not do that as you still have to keep your DEF tank full and operational. To read more about this possible solution, just click on this link. It has more details you should know about that we could not place here.
Some Final Words
Modern engines and their builders have been forced by the government to include certain emission systems. Unfortunately, those new systems are not as good as they could be.
There are user errors, factory errors, and other issues that interfere with the proper function of these systems. When that happens, the check engine light goes on and you face a possible de-rate.
You can take a chance and continue driving or you can park and try to solve the problem. It s a tough choice as some of those check engine lights are faulty and there is no problem.
