Wave Goodbye to Your GMC Duramax Engine Troubles: Decoding the DEF Sensor Quandary

GMC diesel-powered trucks and SUVs have faced some challenges in recent years. The latest models have shown problems with the DEF sensor.

2020 to 2024 model years of the GMC Sierra and Yukon models using a Duramax diesel engine could have malfunctioning sensors related specifically to the diesel engine. The DEF sensor measures diesel exhaust fluid, which is what DEF stands for, and it can cause problems on the roads or trails. Most likely, this sensor problem won’t be felt during normal driving, but when towing or out on the trails, the story could be different for these vehicles.

What does this sensor do?

In diesel-powered vehicles, a DEF tank is present. The sensor measures the amount of fluid in the tank, and if measured incorrectly, a reduced torque output could be the result. This means these GMC trucks and SUVs might not have enough available torque to tow a heavy trailer, resulting in lowered towing capacities. The malfunctioning sensor in these GMC vehicles can get stuck or provide incorrect readings. While this problem doesn’t sound like a serious issue, for owners who need all of the torque these diesel engines can produce, it’s a serious problem.

What happens when the DEF sensor malfunctions?

When the DEF sensor functions erratically, has incorrect readings, or is stuck, the gauge cluster with the warning lights could show a “Service Emission System” warning message. It also provides a “DEF Level Low” message to tell drivers they need to have this system serviced. This means time off the road and in the repair shop, which can be problematic for drivers who use their GMC trucks and SUVs for work. These messages shouldn’t come on because there’s not actually anything wrong with the system, but drivers won’t know when these messages appear on the dashboard.

Does the sensor need to be replaced in these diesel engines?

Thankfully, the fix for this Duramax diesel engine issue is a pretty simple and straightforward process. Service personnel won’t need to replace any parts on the engines; this fix can be carried out by simply recalibrating the system. Service personnel will reprogram the K115 Reductant Control Module in affected GMC trucks and SUVs without replacing any components. This makes the fix pretty easy with a simple service appointment that shouldn’t take very long. Owners can set the appointments and head to the dealership service center for the programming upgrade.

Reprogramming the DEF sensor isn’t all that must be done to correct this issue. In some cases, it might be necessary to add one gallon of diesel exhaust fluid to the DEF tank. This added fluid helps impacted GMC Sierra and Yukon models operate properly.

Why do you have to visit the service center for this fix?

Some of the newest models of the GMC Sierra 1500, Sierra HD, and Yukon vehicle include over-the-air updates. Owners might expect this fix to take place using these updates, which makes sense because the fix is mostly a software upgrade. Unfortunately, a hardwired connection must be used for this programming upgrade. If the connection becomes interrupted, which could happen with a wireless connection, the Reductant Control Module could be damaged. Unfortunately, this means owners must bring their vehicles to the dealership service centers to have this upgrade performed.

Which GMC vehicles are impacted?

Three Duramax diesel engines are impacted by this DEF sensor problem. The engine models and vehicles impacted are:
Duramax turbodiesel 3.0-liter 6-cylinder LM2 engine:

• 2020-2022 GMC Sierra 1500
• 2021-2024 GMC Yukon

Duramax turbodiesel 3.0-liter 6-cylinder LZ0 engine:

• 2023-2024 GMC Sierra 1500

Duramax turbodiesel 6.6-liter V8 L5P engine:

• 2020-2024 GMC Sierra HD

Owners with questions regarding this issue can contact their local GMC Service Center or the GMC customer service center to learn more about the necessary fix for this issue.

Are any Chevrolet vehicles impacted by this DEF sensor issue?

GMC and Chevrolet-branded vehicles utilize the same platforms and engines, which means a selection of Chevy vehicles are also impacted by this sensor problem. These vehicles are the Chevy Silverado, Tahoe, and Suburban trucks and SUVs using the same trio of Duramax diesel engines.

This new programming fix to correct issues with the DEF sensor will give GMC and Chevy SUV and truck owners the confidence and peace of mind required to continue to trust the Duramax diesel engines. Many owners choose diesel engines for the impressive torque figures that make towing and off-roading better. This fix returns maximum torque to these diesel engines.