DEF Light On But Tank Is Full International – Freightliner
While error codes are your friend, they are not that friendly when they malfunction. In fact, it can be downright annoying when they light up and nothing is wrong. This means you have to find the malfunction and get it fixed. That can take some time.
Unfortunately, this may not be an easy fix. There can be several things wrong. One option would be the sensor has gone bad or is stuck. Or it could be the default selection for an SCR-related fault. There are a lot of choices and even mechanics can’t find the source sometimes.
To learn more about this problem and the possible sources, just continue to read our article. It explores the issue so you have the best information possible. Then you can solve it when it happens to you. This article only takes a couple of minutes to read.
What Does it Mean When The DEF Light is Flashing?
When you see the DEF light flashing, it is telling you that your DEF tank is critically low. When you see the light flashing, you need to stop what you are doing and refill the tank.
You cannot keep driving because you will have serious problems if you do. Then if you see the light flashing and the check engine light on at the same time, you are being warned that you are going to be derated.
What that warning light is saying is, that you should have listened to the flashing light, now you have to fill the tank before you get your engine’s power back. Then if you get the ultimate sign you won’t be going anywhere until you refill the DEF tank.
That ultimate sign is the stop engine and the check engine lights are on and the DEF warning light is flashing. The best way to avoid derating and causing yourself and your vehicle trouble are to refill the DEF tank. That is when the DEF warning light first appears and is not flashing.
DEF Light on But The Tank is Full International
The first place you should check is the float. On some models of engines, the float is not stationary. It tends to move about as the fluid moves. However, it can get stuck in one spot.
If you check the float and if it is stuck you may be able to shake it loose or you may need to pull it out and re-install it. But the problem may lie with the pump or the doser valve.
When you get a failed doser unit, the error code should read SPN 3361 FMI 3/3 or fault code 3558. Or you could get fault code 2976 SPN 3361 FMI 2/2. Sometimes you can get the reverse situation.
Your tank is empty but the gauge reads full. This can be troublesome as you will be derated and you won’t understand why. The problem here could be the sensor or float
DEF Light Blinking on Freightliner Tank is Full
Sometimes, the gauge is not at fault nor is the DEF fluid low. You may have a problem with an SCR fault and the default setting is E. Unfortunately, you have to hook up a code reader or scanner, or other devices that find the problem.
The reason you have to do this is that there could be many sources for the problem. In some cases, the DEF metering system could be bad and needs replacing. or there is a problem with the Nox sensors.
One suggestion was to drain the tank and replace it with new fluid. This is a possible cure as some bulk DEF supplies are contaminated before they enter your DEF tank. That can be a possible source of your troubles.
The Nox sensors can trigger a confusing code as well. They may be bad but the code that is sent to you may redirect your attention to the cooling level. This is not an easy issue to solve and it may take a trained mechanic to spot the correct problem.
Make sure to try to clear the code first before taking other actions. Just in case it is a malfunction.
DEF Light on But The Tank is Full Peterbilt
On location when you see the warning light, even if the tank is full, is that there is a problem in the after-treatment system. That was the good news. The bad news is that there are about 250 items that can turn the warning light on even though the DEF tank is full.
Or it is possible that the ECM needs to be updated. With so many possibilities, it is hard to diagnose and give you the definitive answer. The light will come on if there is a problem with the diesel doser that is right next to the turbo.
Some owners are saying that this one light represents far too many issues than it should. That could be by design or it just worked out that way. You should talk to a trusted mechanic who will give you a straight and honest answer to this question.
We say this because the Peterbilt system is not designed for home mechanics to work on. You need a good Peterbilt experienced mechanic to sort out the real source from all the others.
Some Final Words
This can be an annoying problem. Just when you thought you solved your problem by filling up the tank, you find that it wasn’t the DEF level that triggered the error code.
Now you have to go on a treasure hunt to find the real source and it could be just about anywhere. Just be thankful that you did not get the reverse situation. That is where the light stays off, the gauge shows full yet the tank is empty.
Right after that, you get derated. Not a fun situation to be in.
