Maximize Your Mileage: Reset DEF Light and Drive Farther!

You can drive for about 50 miles with the def light on. To reset the def light, you need to refill the def tank with a quality diesel exhaust fluid.

The def light on your vehicle’s dashboard indicates that the diesel exhaust fluid (def) tank is running low, and it needs a refill. Def is an essential component of the selective catalytic reduction (scr) system that controls the exhaust emissions in diesel engines.

Without enough def, your vehicle’s engine won’t start, or it could shut down while driving. So, it is crucial to refill the def tank as soon as possible. Driving with the def light on is possible, but only for around 50 miles. Exceeding that limit could trigger a speed reduction and eventually stall the vehicle. In this article, we will explain how far you can drive with the def light on and how to reset it.

Maximize Your Mileage: Reset DEF Light and Drive Farther!


Understanding Your Diesel Engine’S Def System

If you own a diesel-powered vehicle, you might have come across the term def system. It’s a crucial element that helps your engine run efficiently and comply with emissions standards. Let’s dive deeper into this topic and understand how it works.

What Is Def Fluid?

Def stands for diesel exhaust fluid, which is a non-toxic, colorless liquid. It comprises a 32. 5% urea solution and 67. 5% deionized water and is used to break down harmful nitrogen oxide emissions from the engine’s exhaust. Def fluid gets stored in a separate tank in your vehicle and is injected into the exhaust stream by the def injector.

How Does The Def System Work?

Your vehicle’s def system works in tandem with the selective catalytic reduction (scr) system. Here’s how the process occurs:

  • The engine produces exhaust that flows into the scr system.
  • Def fluid is injected into the exhaust stream behind the diesel particulate filter.
  • The nitrogen oxides in the exhaust react with the def fluid, breaking them down into harmless nitrogen and water vapor.
  • The scr system monitors the exhaust and def levels to ensure that the emissions are within the legal limit.

Why Is The Def System Essential To Your Diesel Engine?

The def system plays a critical role in keeping your diesel engine running smoothly and efficiently. Here are a few reasons why the def system is essential for your engine:

  • It helps reduce harmful nitrogen oxide emissions, making your vehicle more eco-friendly.
  • The def system enhances fuel efficiency, which translates into better mileage, lower operating costs, and reduced environmental impact.
  • In many countries, including the us and the european union, diesel vehicles must comply with strict emissions standards, and def systems help in meeting these requirements.

Understanding your diesel engine’s def system is crucial to keep your vehicle running efficiently, reducing emissions and avoiding penalties. Regular maintenance and timely refilling the def tank can help your vehicle run smoothly and comply with emissions standards.

Common Reasons Why The Def Light Comes On

The def light turning on in your vehicle can be a frustrating experience, but there are common reasons why it may appear. Here are some key things to keep in mind:

Running Out Of Def Fluid

One major reason why the def light turns on is when the vehicle runs out of def fluid. This fluid is crucial to the operation of the selective catalytic reduction (scr) system, which is responsible for reducing emissions from the vehicle.

If the def tank is empty, it can cause the light to come on.

  • Always keep an eye on your def fluid levels to prevent running out.
  • It is essential to replace the fluid at the recommended intervals.

Malfunctioning Def System Components

The def system in your vehicle is a complex network of components that work together to regulate emissions. If any of these components malfunction, it can cause the def light to appear.

  • Malfunctions can include issues with the def injector, pump, or doser.
  • Diagnosing the exact cause of the issue may require the expertise of a trained mechanic.

Faulty Sensors

The def system relies heavily on sensors to detect the amount of fluid, pressure, and temperature within the system. A faulty sensor can cause incorrect readings, leading to the appearance of the def light.

  • Make sure the sensors are clean and free of debris to prevent false readings.
  • If a sensor is faulty, it may need to be replaced.

Environmental Factors

Finally, environmental factors such as extreme temperatures or high altitude can impact the def system’s functionality. This may cause the def light to appear even if the system is functioning properly.

  • If the light appears as a result of environmental factors, it may resolve itself once the vehicle returns to a more favorable environment.

The def light can be an annoying experience, but it is essential to address it promptly to keep your vehicle functioning correctly and to reduce emissions. Understanding why the light appears can help you better troubleshoot the issue and prevent it from happening in the future.

How To Reset The Def Light

Driving with the def light on can be a stressful experience for many car owners. Def stands for diesel exhaust fluid, which is a crucial component in modern diesel engines’ exhaust systems. When the def light comes on, it indicates that there has been a problem with the def system, and the engine’s performance may have been affected.

In some cases, you may also notice a reduction in your vehicle’s power. In this post, we’ll be discussing how far you can drive with the def light on and how to reset the def light.

Step-By-Step Guide To Resetting The Def Light

Resetting the def light requires a few simple steps. Here’s what you need to do:

  • First, turn on the ignition without starting the engine.
  • Next, locate the def reset button. It’s usually located below the steering wheel, on the dashboard.
  • Press and hold the def reset button for at least five seconds.
  • Release the def reset button. You should hear a beep sound, and the def light should go off.
  • Finally, turn off the ignition and wait for a few seconds.

That’s it! Your def light has been reset.

Equipment Needed For The Process

To reset the def light, you don’t need any special equipment. However, it’s essential to have a good understanding of your car’s dashboard and where the def reset button is located.

Safety Precautions To Take During The Reset Process

It’s important to take some safety precautions to ensure a smooth reset process. Here are some tips:

  • Before attempting to reset the def light, make sure that your vehicle is parked in a safe and secure location.
  • Always read the vehicle’s owner’s manual before attempting any repairs or resetting the warning lights.
  • If you’re not confident about the process, seek help from a professional mechanic.
  • Never attempt to reset the def light while driving.

Resetting the def light is a simple process that requires no special equipment. Just follow the above steps carefully, and you’ll be able to reset the def light in no time. Remember to take the necessary safety precautions and seek professional help if you’re not comfortable with the process.

Benefits Of Resetting The Def Light

If you own a diesel vehicle, you are familiar with the def light that appears on your dashboard. This light indicates that your diesel exhaust fluid (def) tank requires a refill. However, what happens when you ignore it or forget to refill it?

The def light may stay on. Resetting the light has various benefits that diesel vehicle owners should know.

Improved Fuel Efficiency

Resetting the def light means that the system recognizes that you have refilled the def tank. As a result, you’ll notice better fuel efficiency since the system operates correctly. The def system ensures that your vehicle’s engine burns fuel cleaner, which results in better gas mileage.

Reduced Maintenance Costs

After resetting the def light, you’ll notice a decrease in maintenance costs. Ignoring the light may damage the engine or other components of your diesel vehicle, resulting in costly repairs. Resetting the light ensures that the def system works correctly, allowing your vehicle engine to perform optimally, reducing maintenance costs.

Longer Engine Lifespan

Resetting the def light ensures that the def system operates correctly, leading to a longer engine lifespan. Ignoring or forgetting to refill the def tank may cause engine damage or other components, decreasing the vehicle’s lifespan. Regular maintenance and resetting the def light often increase engine lifespan, making it run smoothly.

Eco-Friendly Driving

Resetting the def light decreases diesel emissions, making your driving eco-friendlier. Diesel engines burn fuel less efficiently than gasoline engines, reducing fuel efficiency and increasing emissions. Keeping the def system working correctly ensures that your vehicle reduces emissions, contributing to a clean environment.

Resetting the def light has various benefits to diesel vehicle owners, such as improved fuel efficiency, reduced maintenance costs, longer engine lifespan and eco-friendlier driving. Ensure that the light is reset regularly and stop guessing how far you can drive with the def light on by refilling the tank immediately it appears.

Best Practices For Maintaining Your Diesel Engine’S Def System

If you own a diesel vehicle, maintaining its def system is essential to ensure its optimal performance and prevent engine failures. Here are the best practices to follow for maintaining your diesel engine’s def system:

Regularly Check And Refill Def Fluid

Checking and refilling your diesel engine’s def fluid is crucial for optimal performance, and it’s important to keep track of when the fluid needs to be refilled. Here are some key points to remember:

  • Always check your vehicle’s def fluid levels before embarking on long journeys or when the def light comes on.
  • Refill the def tank once it’s down to a quarter tank to prevent damage to the def pump.
  • Use high-quality def fluid to avoid damage to your vehicle’s def system, and always follow the manufacturer’s recommendations.

Schedule Routine Maintenance For Def System Components

Routine maintenance is a crucial part of keeping your diesel engine’s def system running smoothly, and it helps prevent costly repairs. Here are some important points to keep in mind:

  • Regularly inspect the def injector, differential pressure sensor, and def tank heater for damage and wear, and replace any defective components promptly.
  • Schedule routine maintenance for your vehicle’s def system components, following the manufacturer’s recommendations.
  • Clean the def injector regularly to ensure proper functioning and avoid nozzle blockages and engine damage.

Follow Recommended Driving Habits For Optimal Def System Performance

Optimal def system performance is achieved when you follow certain driving habits. Here are some important driving habits to keep in mind:

  • Avoid driving too slowly or too quickly, as these speeds can damage your vehicle’s def system.
  • Keep your vehicle’s speed in the recommended range and avoid sudden acceleration and braking.
  • Always follow the recommended maintenance schedule for your vehicle’s def system components.

Following these best practices for maintaining your diesel engine’s def system can help you achieve optimal engine performance, prevent costly repairs, and extend the life of your vehicle.

Frequently Asked Questions On How Far Can You Drive With Def Light On And How To Reset Def Light

How Far Can You Drive When The Def Light Is On?

You should not attempt to drive your vehicle when the def light is on. This light indicates that the diesel exhaust fluid level is low, and if you continue driving, it can lead to engine damage and costly repairs. Refill the fluid as soon as possible.

What Should You Do When The Def Light Turns On While Driving?

When the def light turns on while driving, pull over to a safe spot and turn off the engine. Check the def fluid level and refill it immediately if necessary. You should also reset the def light afterward to prevent it from indicating another issue.

Can You Reset The Def Light On Your Own?

Yes, you can reset the def light on your own by following the instructions in your vehicle’s owner’s manual. In most cases, this involves turning the ignition on, pressing the menu button repeatedly, and selecting the “def” option, then choosing “reset.

What If You Ignore The Def Light?

If you ignore the def light, your vehicle’s engine performance will gradually decrease until it stops running completely. This is because def fluid is essential for engine exhaust treatment. A malfunctioning def system may also result in engine damage and costly repairs.


Ultimately, it is never recommended to drive with your def light on for an extended period of time. Doing so can cause serious damage to your vehicle and result in costly repairs. Always make sure to refill your def tank as soon as possible and reset the light once the tank has been refilled.

There are several ways to reset your def light, including taking your vehicle to a mechanic or using a diagnostic tool yourself. It is important to follow the proper steps and procedures to ensure that the problem is fully resolved.

Regular maintenance and monitoring of your def system can also help prevent any issues from occurring in the first place. By staying attentive and proactive with your vehicle’s def system, you can ensure a smoother and safer driving experience.