What Does Poor DEF Quality Mean? (How To Fix Poor Quality)
Another item under the hood to worry about. That is the trouble with modern engines. You got a lot of components that can go wrong and DEF is a system that doesn’t take much for it to trigger an alert. The problem is that after the poor-quality light comes on, you are risking worse damage to your engine.
There is a difference in DEF. You can buy good-quality fluid and never see that light or you can save a few bucks and buy lower-quality DEF. The difference is the latter does not slip by the sensors and you end up paying more for the higher-quality DEF when you change fluids.
To learn more about this situation, just continue to read our article. It explores the topic so you can know why you need to spend more and buy the better quality DEF. DEF rep[airs can get expensive if you do buy the lower-quality version.
What Does Poor DEF Quality Mean?
If you go to the dictionary, you will find that the term ‘poor’ means in bad shape, not up to standards, or not looking very good. The term quality is the level of standard the product has been built.
When you put the two terms together, then you get DEF that is not up to the standards it should be when it is labeled poor-quality. It is the inferior fluid that should not be gracing your vehicle’s DEF system.
Other people would say that the wording ‘poor DEF quality’ is in accurate and a better way to state the problem would be "High NOx Emissions Detected" or "Poor SCR Efficiency".
That is because there are other causes that would trigger the poor DEF quality alert light. Those would be:
- Bad NOx sensors
- Contaminated SCR box
- DEF dosing issues
- Potential EGR issue
How To Fix Poor DEF Quality
One option would be to replace the DEF filter, the DEF, clean up the pick-up in the tank, and then do a forced regen. The total cost for this work at the dealer’s is roughly $750.
If you can afford it, that is one way to go. There are other options. One is to replace the parts listed in the previous section. This may be costly but that depends on the mechanic you are working with.
You can try to replace the DEF and then change the NOx sensors. But then if there is an error code, you may have to get the dealer to clear it before the light will go away.
You do need to get this taken care of as quickly as possible as after approx. 200 miles, your vehicle may be limited to 55 mph on the next restart and if you drive further, 500 miles, your vehicle may be put into limp mode.
Poor DEF Quality Freightliner
The issue here is that you can get errors or fault codes if your system detects a lower than expected NOx conversion efficiency. The light will come on after you have added DEF to your tank.
The sources for these codes can be DEF fluid, DEF injector, NOx sensors, or SCR catalyst. To fix this problem the first attempt is to drain the DEF, fill it with new, then change the filter, and do a parked regen. You should also do an SCR conversion efficiency test.
When you replace the fluid, you should leave the key turned on during the draining of the tank. This allows the vehicle to set a code for the empty tank level. Then it will know that you drained and refilled your tank every time after that.
Just keep in mind that this is the most common fix and other techniques may need to be applied if this does not solve it.
Poor DEF Quality Detected Engine in Derate
If you put new DEF inside the tank and there is nothing else added to that tank, then you may have a failed DEF quality sensor. This is what you need to watch out for.
The DEF may not be low quality and you should look for alternative sources to make sure it is not something else. Especially when you filled up your DEF tank from the same refill tank as other vehicles that do not have this problem.
Yes, the fluid can be of low quality, but you should make sure first before assuming it is the fluid’s fault before draining and replacing the old fluid. For the DEF to put your vehicle into derate, you have to drive it several hundred miles with the poor quality light on.
Also, your system will detect poor-quality DEF if that is the problem. This fluid does have a shelf-life and it can degrade if you wait too long to use the fluid. If that is the case, then if you do not drain and replace the fluid, you can hit derate mode.
How To Clear DEF Poor Quality on Duramax
Most likely, you will need a dealer scan tool to delete the codes. Or you can try a manual regen to reset the codes. It is hard to say as the codes will react differently depending on the type of code and if it hit the ECM or not.
If you are talking about the fluid, then all you have to do is drain it, and replace it with new DEF and a new DEF filter.
Some Final Words
While there is a difference between DEF quality levels, it may not be the DEF that is causing you the problems. If draining and replacing the fluid does not work, you can try looking at those other parts that cause this problem.
There are many recommendations to go to your dealer, but that is hit and miss as well. You never know when y u will come across a bad dealer that blows smoke and doesn’t know what the problem is. Pick your dealers carefully.
