Def Pump Not Working : Diagnosing and Fixing

If your def pump is not working, it means that the diesel exhaust fluid delivery system is not functioning correctly. This may be due to a number of causes such as a faulty sensor, a damaged pump, or a clogged nozzle.

The diesel exhaust fluid (def) system is used to minimize the amount of pollutants released in the air by diesel engines. The def system works by injecting a small amount of diesel exhaust fluid into the exhaust stream, which reacts with the engine’s harmful nitrogen oxides and converts them into less harmful nitrogen and water. However, if the def pump is not working, the def system will not work correctly, and the engine may produce more harmful pollutants. Def pump issues can be resolved by identifying the root cause of the problem and replacing any defective parts. Regular maintenance and inspection of the def system can help prevent future issues.

Understanding The Def System And Its Components

Diesel exhaust fluid (def) has been a standard feature in diesel engines since 2010. Its primary purpose is to reduce harmful emissions emitted by the vehicle by converting nitrogen oxide into a less harmful substance. If you’re reading this, there’s a high possibility that your def pump is not working, and you’re wondering what the def system is and how it works.

Overview Of The Diesel Exhaust Fluid (Def) System

  • Def is a non-hazardous solution that comprises 32. 5% urea and 67. 5% deionized water.
  • It is stored in a separate tank and delivered on-demand to the exhaust system.
  • The def injector sprays the fluid into the hot exhaust gas, which triggers a chemical reaction that converts the harmful nitrogen oxides into nitrogen, water, and tiny amounts of carbon dioxide.

Main Components Of The Def System And Their Functions

The def system comprises several components that work together to ensure the vehicle’s exhaust system is operating correctly.

  • Diesel exhaust fluid: def is a solution made up of 32. 5% urea and 67. 5% deionized water. It is carried in a separate container and used on demand.
  • Def tank: this is the container where the def is stored. It is usually located near the vehicle’s fuel tank.
  • Def pump: this component is responsible for delivering and circulating def from the tank to the injector.
  • Def injector: the def injector sprays the def solution into the vehicle’s exhaust system, where it reacts with the harmful nitrogen oxides, converting them into harmless gases.
  • Def lines: these are the pipelines used to transport def from the tank to the injector, ensuring a regulated flow.

Understanding the def system and its components is vital for diagnosing and fixing any problem with the def pump. Always ensure that you use certified def and that the tank is refilled regularly to prevent blockages or contamination that may result in the failure of your def pump.

With this understanding, you can keep your diesel engine running correctly and reduce harmful emissions.

Signs Of A Def Pump Not Working

Diesel exhaust fluid (def) pumps are a vital component of your vehicle’s emissions system. They are responsible for injecting def into the exhaust stream, helping to reduce harmful emissions. But, like any other mechanical part, def pumps can wear out over time and cause a variety of problems.

  • The def warning light stays on
  • The engine power is reduced
  • The def tank is not empty, but the refill light is on
  • There is a strong ammonia smell from the exhaust
  • The engine performance is poor
  • The vehicle cannot complete a regeneration cycle

If you notice any of these warning signs, it’s important to inspect your def pump immediately.

Common Causes Of Def Pump Failure

Knowing the common causes of def pump failure can help you keep your vehicle’s emissions system running correctly.

  • Environmental contamination: dust, dirt, and other debris can cause damage to the pump’s internal components, leading to failure.
  • Incorrect installation: improper installation of the def pump can lead to leaks, damage to the pump, and subsequent failure.
  • Electrical issues: faulty wiring or connections can lead to the def pump not receiving the power it needs to operate correctly.
  • Low-quality def: using low-quality or contaminated def can clog the pump, causing it to fail.
  • Overuse: continual use of the def pump can lead to wear and tear, ultimately leading to failure.

Understanding the common causes of def pump failure will help you take preventive measures and properly maintain your vehicle’s emissions system, ensuring it continues to work correctly.

Troubleshooting: Problem and Fix on DEF/DPF Systems

Diagnosing A Def Pump Not Working

Dealing with a def pump not working can be frustrating and a total nightmare. Why? Most vehicle manufacturers these days are relying on diesel exhaust fluid (def) as an emission control strategy. That means that having a def system failure or error code will cause your truck to fail in emission tests.

It can be fairly challenging to diagnose and repair def pump issues, but that’s what we’re here for!

Step-By-Step Guide To Diagnosing A Def Pump Issue

Whether you are an experienced mechanic or trying to fix the issue yourself, there are some simple steps you can take to diagnose a def pump that is not working correctly.

  • Check engine lights: are there any engine lights or error codes? The first thing you should check when your def pump is not working is the engine lights. Almost always, you can diagnose a faulty def pump through the error codes thrown by the vehicle’s computer system.
  • Check the def tank level: is the def tank full, or almost empty? You must have a minimum quantity of def to keep your truck running. If the def tank is not full, top it up, and see if the error code disappears.
  • Inspect for leaks: is the def system leaking? Def system leaks can cause a low def level. Check for fluid leaks on the ground or beneath the vehicle’s engine.
  • Check the def filter and nozzle: is the def filter blocked or contaminated? A blocked filter will prevent the fluid from passing through efficiently, causing the pump system to malfunction. Also, ensure the def nozzle is free from debris and spray pattern is correct.
  • Test the def pump pressure: is the def pump functioning appropriately? Check the pump pressure and voltage using a multimeter to ensure it is not faulty or damaged.
  • Check the def injector nozzle resistance: is the injector nozzle resistance within the manufacturer’s recommendation? Test the injector nozzle resistance using a multimeter and ensure its value is within the specified range.

By following these six steps, you can diagnose and, at times, fix a def pump issue yourself. However, if the problem persists, it’s essential to take the vehicle to an experienced professional who can accurately diagnose the cause of the error codes.

Don’t let def pump issues get you down; call a professional mechanic to take care of your car if you’re unsure how to diagnose or fix the problem.

Fixing A Def Pump Not Working

Ensuring that your def pump is in good condition is crucial because it helps regulate your diesel exhaust fluid’s amount, which plays a vital role in lowering your vehicle’s emissions. However, just like any other vehicle component, a def pump may experience some glitches, which can hinder its proper functioning.

Simple Fixes That You Can Do At Home

Fixing a def pump that isn’t working may seem like an overwhelming task, but it can be an easy fix that you can do at home.

  • Check your vehicle’s def level: a lower def level can trigger a def pump warning since the device cannot operate with inadequate fluid levels. Always ensure that your vehicle has adequate def fluid levels.
  • Inspect your def nozzles: check your def nozzles for obstructions or damages. If your nozzles are obstructed or damaged, they may hinder the def fluid flow to your def pump.
  • Clean your def pump filter: the def pump filter can become clogged with dirt and debris, causing your def pump to malfunction. Remove your def pump filter and clean it to clear any obstructions.

Advanced Repairs That Require Professional Assistance

Some def pump issues may require more technical expertise and warrant professional assistance.

  • Faulty def pump module: a faulty def pump module may cause your def pump not to work. A qualified mechanic should inspect your def pump module to determine if it’s the root of the problem.
  • Electrical faults: your def pump may fail due to electrical malfunctions, which can cause the device to either stop or function incorrectly. Always seek professional assistance if you suspect an issue with your vehicle’s electrical system.
  • Def pump fluid contamination: if you notice that your def fluid has been contaminated, it’s essential to have it drained and refilled. A contaminated def fluid can cause other engine problems that may result in costly repairs.

Fixing a def pump not working can range from simple fixes that you can do at home to more complex repairs that require professional assistance. Always ensure adequate def fluid levels, check your def nozzles and clean your def pump filter to prevent basic issues.

However, when you discover more complex problems, it’s advisable to seek professional assistance.

Maintaining Your Def System

Def Pump Not Working – Maintaining Your Def System

As a vehicle owner, maintaining your def system is crucial to ensure the longevity and efficiency of your vehicle’s diesel exhaust fluid (def) pump. Neglecting your def system can result in expensive repairs and decreased fuel efficiency, which nobody wants.

Here are some tips to keep your def system in good working condition.

Tips To Keep Your Def System In Good Working Condition

  • Regularly check your def levels: checking your def levels frequently can help you avoid running out of def, which can lead to the def pump malfunctioning. A good practice is to check your levels every time you refuel your vehicle.
  • Use high-quality def: using high-quality def is crucial as low-quality def can cause clogs or damage to the def system components. Always choose def that complies with iso standards to ensure your vehicle runs smoothly.
  • Store def correctly: def should be stored in a cool, dry place, away from direct sunlight. Exposure to sunlight can cause def to chemically react, resulting in poor quality. Always store def in a sealed container to prevent contamination and evaporation.
  • Maintain the def tank: regularly cleaning the def tank can prevent buildup and contamination. A dirty def tank can cause clogs and damage to the def system components. It is essential to clean your def tank every year or as recommended by your vehicle’s manufacturer.
  • Don’t mix def with other fluids: never mix def with other fluids like diesel, motor oil, or coolant. Mixing def with other fluids can cause corrosion, clogging, and damage to the def system components.
  • Avoid using contaminated def: always use clean and uncontaminated def for your vehicle. Using contaminated def can cause your def system to malfunction, leading to expensive repairs.
  • Follow the manufacturer’s recommendations: always follow the manufacturer’s recommendations for maintaining your def system. Refer to your vehicle’s owner’s manual for specific maintenance procedures and recommended products.

By following these simple tips, you can ensure your def system’s optimal performance and avoid costly repairs. Regular maintenance of the def system is essential to keep your vehicle running efficiently, while also helping to reduce harmful emissions, making it better for the environment.


To sum up, a def pump plays a crucial role in operating your vehicle efficiently. A def pump not working can result in various issues, including a decrease in fuel economy and a considerable impact on the environment. However, if you experience any issues with your def pump, you don’t have to worry.

The most common causes of def pump failure are easily repairable with simple tools and by following the guidelines provided by the manufacturers. Be vigilant about your vehicle’s maintenance, keep an eye on def tanks’ levels, and promptly address any issues with def pumps.

Hopefully, this blog has helped you understand the importance of def pumps and how to prevent their malfunctions. Remember, stay up-to-date with your vehicle’s maintenance and enjoy a smooth, trouble-free ride.

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