How To Reset The Exhaust Fluid System Fault On A Ford Diesel Truck

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Written By Thomas Anderson

Even if you’re environmentally cautious or not, the Diesel Exhaust Fluid or DEF is a must-have in your truck’s system, or else it won’t operate at all. So, if you’re a Ford truck owner, it’s better to stay aware of how to reset the exhaust fluid system fault on a Ford diesel truck.

To reset your engine system properly, you’d have to disconnect the negative battery cable and let your engine drain away all its power by waiting for about 30 minutes. This will force the computer to reset on its own. Later on, you need to use a code reader, pour in enough DEF, and take the vehicle to a repair shop

However, if you’re not careful enough, one small mistake while resetting can make you go through a lot of hassle, so you need to know other relevant information relating to DEF. 

A Brief Overview Of The Diesel Exhaust Fuel System 

Diesel Exhaust Fuel or the DEF system have been introduced as an initiative to protect the environment from harmful fuel by-product emissions.

This is a clear solution that consists of urea and water in a ratio of 1:2. It is directly connected with and injects to the Selective Catalytic Reduction or SCR

It converts the toxic emission gases into Nitrogen and Carbon dioxide, which flow out your truck’s tailpipe. 

Now, its function might seem simple, but a little issue concerning it can take your vehicle to the repair shop for days, costing you a fortune.

We mean…the blood circulation of the vehicle, that is, the whole fuel system can get ruined if the DEF system is taken care of. 

Resitting is the most common practice undertaken to solve fuel system and sensor issues. Read along to learn how you can reset your Ford truck in this case! 

How To Reset The Exhaust Fluid System Fault On A Ford Diesel Truck

Resetting could stand for a few possible methods, but in this particular case, we’re referring to letting your Ford truck adapt and learn new changes after an issue gets fixed. 

DEF system fault is a common issue for more or less all types of vehicles containing this system.

But truck owners have been reported to face it more frequently. The Ford F-series, 6.7 L PowerStroke trucks, fall under that category. 

Nevertheless, the resetting procedure is almost similar for most truck models and brands. 

If you own a Ford truck, you’d have to take into account the following steps carefully:

1. Stationary Reset

As mentioned earlier, when it’s just an issue with a low range of exhaust fuel and if your vehicle is not resetting even after getting filled, it’s recommended to perform a stationary reset.

You can do so by parking the truck on the ground level. After pouring in more than a gallon of DEF, you can let the truck idle for some seconds. And then drive the vehicle at a speed of 6 MPH for about 3 minutes. 

2. Resetting Engine Computer

Firstly, you need to look under the hood. Using a ratchet or a socket, you’d have to loosen the lock nut on the connector connecting the negative battery cable. 

The connector of the negative battery has to be pulled off the terminal.

Secondly, you’ve to wait for about 20-30 minutes to let the engine computer gradually drain out the backup power it holds. Once it’s completely out of power, it’ll begin to reset. 

Make sure to tighten the nut you loosened earlier and have joined the negative battery connector.

Now, if your engine system still doesn’t reset and you see the same message of information on your dashboard, you might have to consider another additional step. 

3. Clearing Fault Codes

Fault codes can be cleared using the previous method, but it’s better to look into it more and be aware of what it indicates. 

If you’ve received the P20EE fault code, your priority should be to take your truck to the repair shop or your dealership as soon as you can.

But before that, you could use an OBDII scanner to clear the fault code or the engine warning light. Disconnecting the car battery for half an hour can also help in clearing the codes.

Turning on ignition power using the key but not starting the car for about 30 minutes can help similarly. 

Make sure to follow the owner’s manual for the warning messages you receive and for all the other tasks you try on. 

Note that, although resetting does the job precisely, doing it on your own might not be the best option at all times because you can face the DEF system issues anytime. 

If these aren’t taken care of properly, you might have to replace the whole fuel system, which would cost you about $2,500-$5,000. 

So, you need to stay aware of the ways we could take care of your truck’s DEF system.

Things You Need To Be Aware Of Before Resetting The DEF System Fault

The very first indicator of a DEF issue is if you see a red Engine Warning Light and hear a continuous chime. Although you need to get an alert right then, you should take the time to check out for other warning signs. 

Let’s explore the things you should keep in mind before deleting or resetting your truck’s engine program.

1. The Type of Warning Message

Ford trucks show a variety of information, reminder, and warning messages as a form of Driver Information Centre (DIC) message. 

In case of DEF issues, we can classify them into two groups: 

2. Exhaust Fluid Range Message

Based on how much exhaust fluid is left or running on an empty tank, your Ford truck will display a message stating what action you need to take.

If the fuel level is less than half-filled, the message will tell how many more miles you can go on with the remaining bit. Following that, you can just fill up the exhaust fuel tank as per your availability.

But when the exhaust tank is almost empty, you’ll receive a reminder message that’ll tell you that after you’ve crossed a certain amount of miles. And your speed will be limited. 

For Ford trucks, it shows you have about 5 miles to cover before your speed gets limited to 50 MPH

If you still don’t fill up after getting the reminder message, your speed will get confined just after restarting the next time or will start right on.

Note that, it won’t run on limp mode, the speed would just not get over the limit, and you have to run it as it is. 

Now, these are the issues that can cause your speed to be constant, which isn’t fun. But things can be much worse if you don’t act fast and fill up the fluid tank.

If the Selective Catalytic Reduction or SCR system detects the low range of exhaust fluid or additional issues with the SCR system, your truck will run in an idle-only mode.

That is, your engine will be idled, and the message you’ll receive will tell you to operate using the owner’s manual. 

You might have to reset your truck based on how your truck responds after being filled for all of the cases mentioned above. Then wait and check if the engine computer resets after being filled up. 

When the system gets aware that the tank has been filled, it resets the data on its own. 

But sometimes, your vehicle might not be able to tell for probable troubleshooting issues. You’d then have to shut off and restart your engine a few times.

If that still does not work, you might have to take the route of resetting without wasting any time.

3. Exhaust Fluid System Fault Message

If you receive messages that end with “…for exhaust system fault”, that means this warning has nothing to do with the amount of exhaust fuel there is. There are other issues with the system or component you should take care of as soon as possible.

Contaminated DEF fuel plays the biggest role here. A lot of people make the mistake of pouring in DEF on the diesel fuel tank and vice versa. 

DEF can also get frozen in low temperatures. If the solution is not clean, it won’t be able to function and ruin the other components.

You’d also receive these messages if the DEF tank sensors are not working well or the SCR system becomes faulty. 

If you’re on the run and to survive right then before reaching the repair shop, you can try reprogramming and resetting. But change the faulty parts and fill in enough clean DEF as soon as possible.

You might be able to catch fault codes if you’re using a scanner or any other tool, and that would make the diagnosis and repair process easier to understand. 

4. The Diagnosed Trouble Code

P20EE is the fault code you’d get if emission has increased in the exhaust system. This means that there must be pollutants or contaminants presenting the system.

The code won’t automatically shut you down. But it’s suggested to get the code read and cleared as soon as possible. 

As an emergency step, make sure to pour in extra DEF before getting the code cleared.

The code plays an important role because it’ll be easier to reset your truck later on, depending on the data it provides. 

You’re good to go once clearing and resetting are done, but you do not want it to happen frequently. Hence, stepping up and taking preventive measures are a must. 


4 Ways You Could Prevent Frequent DEF System Failures 

Just as people say, prevention is better than cure, and it couldn’t be any more true in this case. 

You can take care of your truck’s DEF system the following way:

1. Make sure to pour your DEF into the right tank and more than 1 gallon at once. The one you’d be looking out for here is the blue cap one. To stay away from making any silly mistakes, do not open the fuel and the DEF cap at the same time.

2. Use DEF fluid which contains the API certified or ISO 22241 label. Using any other DEF fluid might end up ruining your system

3. Since DEF is prone to freeze in low temperatures, you should keep your truck in a warm garage during winter.

4. Check your DEF fuel rank and keep it filled ⅔ portion to avoid getting the warning messages and to ensure a long life for your fuel system.

Adopt these steps to sustain the life of your Ford truck and make sure to abide by the owner manual.


1. Can disconnecting the battery result in deleting important information?

No, the battery being removed will only reset certain values that are in volatile memory but will not delete any data relating to the ECU map. If this was the case, then your vehicle would reset completely to its factory version every time the battery gets disconnected.

2. What is the best DEF to use for Ford trucks?

Ford recommends using the Motorcraft DEF which works perfectly for all the Ford Diesel Engine vehicles, especially the PowerStroke trucks. User experience suggests that Motorcraft DEF does not create any vehicle warranty issues.

3. At what temperature should I preserve the DEF?

Since DEF can freeze up easily in low temperatures, you need to be aware of where you store the fluid jug. Make sure to keep it away from direct sunlight and in an area with a temperature reading between 12-65° Fahrenheit. 

You should also use a DEF heater for your vehicle.

4. How many miles can I run while filling one gallon of DEF?

Be it a full tank or not, the amount of miles you can cover depends on your mileage. But in general, with one gallon of DEF at the tank, you should be able to run about 300-500 miles.


You most probably have installed the fact in your head that a DEF system can be deadly for you and your truck and hence, having a clear knowledge on how to reset the exhaust fluid system fault on Ford diesel truck– can make your life easier.

Make sure to get enough DEF and fill the tank at the right time. A full-functioning DEF system is what you should be yearning for. Best of luck! 

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