What to Do When Service Exhaust Fluid System Message Pops Up?

Meeting emission regulations standard in diesel engines is hardly possible without a properly functioning exhaust fluid system; hence, the service exhaust fluid system warning signal requires immediate attention if you suddenly discover it on your truck.

The system is designed to run on DEF fluid which is subject to exhaustion. Running out of this fluid or experiencing the system warning message is not good for your engine. Therefore, you must find a way out as soon as possible.

However, not to worry! This article explains what the exhaust fluid system and the warning light mean, as well as the solution to the problem if it ever occurs in your vehicle.

service exhaust system

What is Exhaust Fluid System?

Several systems have been built in various vehicles to enable car owners to overcome emission regulations. Besides the EGR (exhaust gas recirculation) system and DPF – diesel particulate filter, the exhaust fluid system is also designed to enhance a vehicle’s ability to operate proper emission.

The exhaust fluid system is responsible for minimizing the emissions of nitrous oxide (NOx), enabling a vehicle to meet the emissions regulations standard. This is common with diesel-powered truck engines. The system works with diesel exhaust fluid, popularly known as DEF.

The fluid is as important as other fluids in a vehicle. This is because running on a low DEF fluid level can affect the vehicle’s engine as much as a low engine oil level can also impact an engine. However, let’s see how the exhaust fluid system works to appreciate it better.

How Exhaust Fluid System Works

The exhaust fluid system runs on diesel exhaust fluid (DEF), which is an aqueous urea classified solution comprising 32.5% of urea and about 67.5% of deionized water. The objective of the system’s operation is to minimize air pollution caused by diesel engines.

This is how the whole operation works. The diesel exhaust fluid (urea solution) is injected into the vehicle’s exhaust upstream of the selective catalytic reduction (SCR) catalyst in order to vaporize and decompose into carbon dioxide and ammonia.

The ammonia synergizes with the catalyst to convert harmful emissions (NOx gases) into harmless nitrogen and water. With this operation on, diesel trucks are able to reduce air pollution to meet emissions standards.

Unfortunately, the DEF fluid is not inexhaustible. The exhaust fluid system requires a constant refill of the fluid to keep it running smoothly. Otherwise, it may trigger a service system error signal in the vehicle.

For instance, the service exhaust system in a Duramax diesel engine can pose a serious challenge if not rectified immediately. Let’s see what the warning signal means below.

What Does Service Exhaust Fluid System Mean?

Service exhaust fluid system signal means something has tampered with a vehicle’s DEF system, thereby displaying a DEF-related trouble code on the dashboard.

When this message surfaces, it necessitates immediate action to prevent the system from further damage that may be costly to fix. Typically, every truck has a designated warning light on the dashboard that triggers whenever you’re running low on diesel exhaust fluid.

So, the driver’s responsibility is to study this warning signal and top off the fluid when necessary in order to avoid any costly damage. The service exhaust fluid system in a 2011 Duramax is a critical issue if you drive a truck with the diesel engine.

However, if you’re experiencing the service exhaust system warning signal on your dashboard, there’s a way out.

Diesel exhaust fluid

How to Fix Service Exhaust Fluid System

Once you spot the service exhaust fluid system signal on your vehicle’s computer system, ensure to fix it immediately. These service exhaust fluid system reset tips will help you resolve the issue in a few steps. The guide below is for a 2011 GMC Sierra 2500 HD. It can also fix the issue with other diesel car models.

Test the reductant fluid heater

The reductant fluid heater is responsible for preventing the diesel exhaust fluid (DEF) from freezing in low temperatures. You may want to check out the component if you suddenly see the service DEF system warning message.

So, get a digital multimeter to test for the resistance. Before that, carefully disconnect the vehicle’s Glow Plug Control Module. Then, test the resistance level on the (orange/white) pin 11 and the ground. It should be within 2 – 4 Ohms.

Replace the reductant fluid heater

If the reductant fluid heater resistance level is inaccurate, you may have to replace the component immediately before proceeding to the next step. However, kindly move to the next step below if the resistance level is okay.

Reset the exhaust fluid system

Get a working scan tool that can reset a DEF system and plug it into the scan port beneath the dashboard on the driver’s side. Turn on the scanner and navigate to “Module Setup.” Then, go to “Reductant Fluid.” Thereafter, move to “Tank Level Reset” and reset the system. This will reset the warning to “None.”

After that, navigate back to “Reductant System Data Reset” and engage the reset again here. However, this will throw on the warning signal in a moment and take it out again after a while. Now you’re good to go! You may want to use this video for further guidance.

This recommendation can also be helpful in fixing the service exhaust fluid system in a Chevy Duramax.


How do you clear a diesel exhaust fluid system?

A contaminated diesel exhaust fluid (DEF) system can be cleared using a vinegar solution. Meanwhile, this is how to clear the service exhaust fluid system in your truck: Mix 1 part of vinegar with 3 parts of water.

Then, pour the solution into the diesel exhaust fluid tank. After that, start the truck and run the engine for around 30 minutes. This will allow the vinegar solution to simply reach the pump. After that, drain out the solution and refill the tank with new DEF fluid.

What happens if you drive without DEF fluid?

Driving without diesel exhaust fluid (DEF) will automatically reduce your truck’s engine performance and alter its speed levels. The DEF fluid is a necessity, especially for trucks produced after 2010. It breaks harmful emissions down into non-toxic nitrogen and water.

The DEF fluid reduces emissions by up to a whopping 90%. So, running out of DEF fluid may trigger a service exhaust fluid system in a 2016 Duramax or any diesel car model.

How do you reset the diesel exhaust fluid on a Chevy?

Resetting the DEF system in your Chevy is the best way to deal with the sudden trouble code on the dashboard. Here’s the process in a few steps: First, test the reductant fluid heater’s resistance with a multimeter (it should be between 2 and 4 Ohms).

After that, connect a scanner to the scan port beneath the vehicle’s dashboard on the driver’s side. Next, go to module setup > reductant fluid > tank level reset. Then, engage the reset. After that, go back to the reductant system data reset and engage the reset too. Wait a while, and you’re done!

How often should def fluid be changed?

Changing your diesel exhaust fluid (DEF) is determined by the amount of fuel your truck consumes. The DEF fluid is consumed at around a 2% – 3% rate relative to the quantity of fuel you use. In other words, a truck using a 65-gallon tank will require up to 1.2 – 2 gallons of DEF fluid.

So, it is advisable to change your truck’s DEF fluid every 3rd to 4th time you refill the diesel fuel tank, especially if the truck runs on a 5-gallon DEF tank. This can help prevent service exhaust fluid system in a 2017 Duramax.

Why does my truck say service exhaust fluid system?

If your truck’s dashboard is displaying a service exhaust fluid system, it simply means the DEF system has been tampered with. Therefore, the trouble code surfaces as a warning signal requiring a quick fix of the malfunction.

Ensure to rectify your truck’s DEF system if you ever come across this warning message at any point in time. Fixing the problem can be pretty easy.

Will low DEF make the check engine light come on?

Not at all! Although various malfunctions can trigger a vehicle’s check engine light, low DEF may not directly trigger this signal. However, running on a low diesel exhaust fluid level puts your truck’s engine at a big risk.

If the fluid eventually runs out, it will reduce the engine power and immediately affect the vehicle’s speed level. In that case, a related fault may trigger the check engine light. Ignoring the DEF system causes a malfunction and triggers the service exhaust fluid system in a 2019 Duramax or your respective car model.

Final Words

You shouldn’t panic because of the service exhaust fluid system warning signal. It is not the end of the road for your truck’s engine. However, if you continue to defer resolving the service exhaust fluid system in your diesel truck, you may as well be playing with a potential engine disaster.

So, why not follow the recommendations in this article to fix the issue immediately? Nevertheless, ensuring that you never run out of diesel exhaust fluid will go a long way to protect your vehicle’s engine and enable it to reach its lifespan. So, this should be a priority.

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Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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