How to Clear Service DEF System Message Duramax – 4 Methods

How to Clear Service DEF System Message Duramax? DEF is an essential component of modern diesel engine technology as it helps reduce harmful emissions by converting nitrogen oxide into harmless water vapor and nitrogen gas. Among the top diesel engines is the Duramax General Motors, which has used DEF in its heavy-duty trucks since 2011. 

Sometimes when you derive a Duramax vehicle, you may have encountered the frustrating “Clear Service DEF System Message” on your dashboard. This message indicates an issue with your diesel exhausts fluid (DEF) system and requires attention to clear it. Then

This article will guide you through the steps necessary to clear the service DEF system message on your Duramax. We will also provide some helpful tips to prevent this warning from appearing.


When you are driving a diesel engine-driven vehicle and suddenly see a max speed limit of 4 MPH until 73 miles, you see a pop-up on your screen; it could be an issue with the DEF DPF system.

If the diesel exhaust fuel is lower than 2 gallons, the system may malfunction and cause your vehicle to slow down.

A new policy has been implemented that will introduce three stages of speed limits for a particular highway.

  • The first stage consists of a maximum speed limit of 65 mph until you drive 73 miles. This means that drivers can maintain a consistent speed while traveling long distances.
  • The second stage occurs when drivers reach 73 miles on the highway, and the maximum speed limit is reduced to 55 mph for the next 72 miles.
  • In the third stage, your vehicle’s maximum speed will be reduced to a mere 4 mph until you have driven a distance of 73 miles.

How to Clear Service DEF System Message Duramax [04 Methods]

How to Clear Service DEF System Message Duramax


There are four ways to clear services DEF system message Duramax. Now see in detail all these methods.

By Refilling DEF:

DEF is not a fuel additive or cleaner, but it works alongside the engine’s exhaust system to reduce NOx levels by converting them into harmless nitrogen and water vapor. Unlike traditional fuel additives or cleaners that are added to the fuel tank, DEF is stored separately in an entirely different tank under the hood.

How to Clear Service DEF System Message Duramax [04 Methods]


The DEF tank typically sits on the vehicle’s front passenger side behind the engine block. You can quickly identify it by its blue cap color, differentiating it from other fluid containers in your car.

While refilling DEF may seem like an added chore every 6000 miles, after filling the tank with DEF, it’s important to start the vehicle and let it idle for 50 seconds. The message will disappear after 5 minutes at a lower speed.


By Resetting with a Scan Tool:

By Resetting with a Scan Tool:


The good news is that you can reset the exhaust fluid system and clear the service DEF message in 7 simple steps with the help of a scan tool.

  • In the dashboard, connect the scanner to the scan port
  • Click the ‘Module setup’ by turning on the scanner.
  • Click on the ‘Reductant’ fluid and then click the ‘Tank level reset’ option.
  • Now reset the system, and the warning sign will be removed.
  • Return to the ‘Reductant Data Reset’ and click the reset again.
  • It will briefly show the warning and then clear again.
  • And the system will reset successfully.

If you cannot reset it, contact the mechanic for help.


By Disconnecting the Battery Cables:

How to Clear Service DEF System Message Duramax [04 Methods]


Some users say removing the max speed limit 4 mph warning from their vehicles is as easy as disconnecting both negative battery cables for 30 seconds. This will automatically reset the system, and any problems should be solved.

Remembering that this solution may not work for all vehicles or situations is important, so it’s always best to consult a professional mechanic before attempting any repairs.

By Disconnecting the ABS/Speed Sensor:

By Disconnecting the ABS/Speed Sensor:


If the first one doesn’t work as planned, don’t get discouraged – another method may do the trick. The first option is disconnecting the ABS sensor, which can help to remove the speed limit.

If you’ve tried disconnecting the ABS sensor and still find yourself limited by a speed restriction, you can try disconnecting the speed sensor on the transfer case. When you disconnect the ABS sensor, the message will disappear.

It’s important to note that this option should only be attempted if you are experienced with vehicle maintenance and have researched how this modification could affect your car’s performance and safety features.


Final Thoughts:

We discuss in detail How to Clear Service DEF System Message Duramax? Adding DEF after every 6000 miles is crucial in maintaining your vehicle’s performance.

Ignoring this can result in a service DEF system message appearing in your DIC and a reduced max speed of 4 miles per hour. If you encounter this problem, the temporary solutions mentioned above can help eliminate it. 

It’s important to prioritize preventative maintenance to avoid such issues altogether. So, don’t forget to add DEF to your vehicle regularly and ensure a smooth driving experience for yourself and others on the road.


Can DEF affect fuel mileage in Duramax 6.6?

The simple answer is yes, but not necessarily in a negative way. When properly used, DEF can improve Duramax 6.6 fuel efficiency by up to 5%, allowing the engine to burn fuel more efficiently while reducing pollution levels emitted by the vehicle. If you want to get better fuel mileage in Duramax 6.6

How DEF reduces white smoke in Duramax.

To effectively reduce white smoke emissions, you must ensure you use high-quality DEF fluid and regularly check its level. The Duramax engine requires a specific ratio of DEF to diesel fuel, so it’s crucial to follow manufacturer recommendations for DEF usage.

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