What Is the P249D Code on Duramax & How to Fix It?

Are you tired of refueling your Duramax now and then? Well, you are not the only one suffering from this problem. Code P249D has been thrown at many others by their trucks.

What does code P249D mean on Duramax, you say? This code indicates that the quantity of DEF delivered to the catalytic reduction system of your Duramax is relatively low. This causes harmful NOx to be left in its raw form. This is neither good for the environment nor the engine.

There’s no need to be alarmed if this code appears on your Duramax; in this article, our focus will be on what the code means, its problems, and fixes.

P249D Code On Duramax

What Does The P249D Code Mean For Duramax?

As previously stated, when the ECM detects a decrease in the exhaust fluid and then sets this code. However, what does this code particularly state? Let’s look at that!

  • P = Powertrain specifies the collection of components that help move the car.
  • 2 = This is a manufactured specific digit that helps identify the model of the truck.
  • 4 = Auxiliary Emission Controls
  • 9D = This part of the code represents a particular fault index that indicates malfunctions in the fuel injector circuit in this case.

According to this code, if there is a problem with the injector circuit. This means that the delivery of DEF to the engine is not as efficient as it should be. This affects the engine’s longevity by interfering with the catalytic converter system.

Read Also: How to Fix P205B Code On Duramax?

How Serious Is The P249D Code On Duramax?

Almost every fault code, along with this one, is quite severe and is not meant to be neglected. After all, that’s the sole purpose of vehicle developers’ dumping fault codes in the engine’s program unit.

That being said, the code P249D is pretty serious once it appears on your Duramax. It’s not something you can ignore and think of getting fixed later someday.

Furthermore, if you plan on ignoring this code and working around it without fixing anything, you’ll be doing more harm than good to your Duramax engine.

Hence, as the code suggests, a minimal exhaust fluid is injected into the engine. The engine performs inefficiently, and its peak performance falls significantly below average.

Moreover, less fluid for the engine also means that the engine would have a higher chance of damage due to harmful particles being left in it. Thus, the components of your Duramax engine wear off more frequently than usual.

Read Also: How to Fix The P0571 Code On Duramax?

What Causes The P2249D Code On Duramax?

Since the code P249D indicates less DEF injection to the engine, it probably has something to do with the engine’s DEF injection. However, there’s more to it. Let’s see a few other causes of this issue.

  • The leaking of exhaust.
  • The fuel is too contaminated for proper use by the engine.
  • The malfunctioning of the DPF (Diesel Particulate Filter).
  • A damaged NOx sensor on Duramax could lead to this.
  • Clogged Fuel Injectors.
  • Too much accumulation of harmful exhaust particles on the NOx sensor.

Read Also: How to Fix The P0381 Code On Duramax?

How To Fix The P249D Code On Duramax?

To fix the code on Duramax, you need to be mentally and physically prepared for things to go smoothly. Hence, you cannot go on being carefree when trying to resolve the issue. Now let’s see the steps!

Step 1: Pinpoint The Root Of The Problem

Before any diagnostic steps to fix the issue, you might need to ensure that the code indicates a valid problem. So you need to conduct thorough investigations to ensure something is wrong with your Duramax.

Once you know that the code is there for a prominent reason, you can do everything necessary to jot out the source leading to this issue. Now that could either be damaged or faulty parts.

Step 2: Replace the DEF Injector

This sould be located between the DPF housing and the SCR housing and attached to the mixer chamber. Hence, unscrew the nuts holding the injector and then disconnect it. Then install a new one.

Step 3: Replace The NOx sensors

The NOx sensor is placed just before the SCR system. Try to unplug the sensor from the connections it’s attached to, and then bring in a new sensor and connect it to the vacant sockets. After that, check the sensors!

Step 4: Reassure That The Problem Has Been Completely Resolved.

After all the cleaning and repairing are out of the way, you must ensure that your Duramax diesel engine is wholly lubricated to prevent further wearing and tearing of the engine.

Then do a quick scan of the Duramax engine to see if the problem persists. If no further signs of damage exist, you’ve fixed the issue, and the code should go away.

Read Also: How to Fix P0671 Code On Duramax?

Other Symptoms Of Getting P249D Code On Duramax

Now, several symptoms lead to this problem. We may already know what causes the problem, but sometimes we must understand the signs that come along with this.

Diagnosing the symptom may help pinpoint the source of the problem itself and make the process of resolving the issue feel much quicker. Hence, let’s look into those.

  • Problems with the turbocharger itself.
  • Poor exhaust performance.
  • A shallow fuel economy.
  • Drastically low engine performance.
  • Idling of the engine.
  • The engine loses power when driving.
  • Problems when trying to start the engine.

Read Also: How to Fix P0101 Code On Duramax?

How Much Does It Cost To Fix the Duramax P249D Code?

Like any other problem related to such fault codes, it’s relatively expensive to fix these fault codes on your Duramax. But that value may differ quite heavily depending on your location.

Moreover, if you decide to get the job done by a mechanic, you will save a few bucks, but that would cost a lot of your labor hours.

However, if you have the extra cash to spare, then it would be best to invest in getting this problem fixed by a mechanic. Investing in a professional may only cost you between $75 and $150.

Furthermore, replacing the fluid system itself may cost you somewhere between $400 and $800.

Can You Drive Your Duramax With Code P249D?

It’s not wise to drive with an incorrect code on your Duramax. Moreover, nobody loves driving with the check engine light glowing every time you start your Duramax.

Furthermore, driving with such an issue may cause the engine to become damaged by the accumulation of harmful particles. Thus, the engine wears out much quicker than normal, reducing its longevity.


Since we’ve reached the final part of this topic, we hope you’ve understood the importance of getting the fault codes on your Duramax fixed as soon as possible.

Hopefully, if you haven’t missed a beat throughout this write-up, you should be more than prepared to get the fault code showing up on your Duramax resolved. We’ve enjoyed sailing with you through this tiresome sea of queries regarding the fault code. We made sure to cover everything you need in this write-up. Hence, keep an eye out for fault codes.

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