How to Fix the P20EE Code on Duramax (Step-by-Step Guide)

Oops! Your Duramax OBD system is showing the error code P20EE and you don’t know anything about this! Seems too difficult? No worries, it won’t be that tough if you can diagnose the trouble code accordingly.

P20EE is a diagnostic trouble code that means “SRC NOx Catalyst Efficiency Below Threshold”. It is the case of reduced catalyst efficiency of your Duramax diesel engine. However, there will be some symptoms and thus you will understand where exactly the problem is.

No hurry, just go through the article.  Today we are going to give you a detailed overview of the P2OEE code and how it causes problems on Duramax. Plus, there are also some symptoms figured out. Finally, you have the solution process.

How to Fix the P20EE Code on Duramax

What Does the P20EE Code Mean On Duramax?

The DTC code P20EE represents “SRC NOx Catalyst Efficiency Below Threshold”. Here the full form of SRC is a “selective catalytic reduction catalyst”. It is the property of the diesel engine of Duramax.

This diagnostic trouble code is the indicator of reduced catalyst efficiency in the diesel engine. If the PCM finds that the selective catalyst is lower than the threshold on bank 1, this could be displayed.

In general, the DTC or diagnostic trouble codes include 4 parts. Here,

  • P= Powertrain, the system of components that propels your car forward (Here, it is the diesel engine)
  • 2 = A generic number
  • O = Threshold on bank 1
  • EE = Specific fault index (Here, this demonstrates reduced catalyst efficiency)

How Serious Is P20EE Code On Duramax?

If you detect P20EE Code, you had better stop the car and check. However, if there is any code reader or you can clear the code anyway, you can drive.

Nonetheless, there might be some indicators like system warning messages, engine performance downfall, or reduced fuel efficiency. Plus, you may also notice exaggerated black smoke, active check engine light, or even missing the PDF regeneration. These are some of the most common symptoms of the Duramax P2OEE error code.

Usually, it shouldn’t shut you down from driving if the P20EE code is found. If you ask us for an expert opinion, we suggest pouring the tank with some fresh DEF fluid. You can get the DEF at any nearby local car shop.

So, you had better use fresh DEF before you drive again. And then, step ahead and follow the below procedures to fix the error code thoroughly.

What Causes P20EE Code On Duramax?

Being a generic code, the code P20EE may come with different triggers. There are some common reasons to cause a P20EE code on your Duramax. To point out the most common causes of the P20EE Code On Duramax, we can see:

  • SRC failure
  • Damaged connections    
  • Faulty circuit       
  • Bad DEF    
  • Poor exhaust gas or temperature sensor
  • DEF injector downfall and Control module problem       

Typically, these are the most common causes of this particular error code on a Duramax vehicle. 

How To Fix P20EE Code On Duramax?

As you are searching for fixing the P20EE Code on your Duramax, we have covered a guide to help you.

To diagnose and fix the P20EE Code, you have to check all the cases properly. We suggest you check for reasons and symptoms that may cause the trouble code.

Let’s now know how to diagnose the P20EE code and what to check one by one.

Check 1: Selective Catalytic Reduction Catalyst Failure

The SRC system or selective catalytic reduction catalyst might malfunction if the sensors and circuits don’t function properly.

Solution: Firstly, you have to fix the exhaust emission leaks.

Check 2: Damaged Wires And Connections

Check whether there are any broken wires or if the fuse is alright or not.

Solution: Before fixing the trouble code, you had a better repair or replace the faulty connections and defective fuse.

Check 3: Poor Exhaust Gas or Temperature Sensor

If you find that the O2, NOx, or exhaust gas temperature sensor is damaged, then there you will need to work with these factors. Follow the solution as given.  

Solution: Fix the exhaust gas or temperature sensor. Even if the P2OEE code still arises, you had better take professional help.

Check 4: Bad Diesel Engine Fluid

It’s time to go through the diesel engine fluid reservoir and check Whether there is any defect or not.

Solution: Once it is contaminated, you have to change the fuel filters and injectors. Besides, give a check over the HP fuel pump. If there is any contamination, change it as well.

Check 5: Issues on Control Module

In case of any PCM issues, then you will need to work there. 

Solution: The PCMs are designed specially and you may need software to program it. Try to work with software.

Other Symptoms Of Getting P20EE Code On Duramax:

P20EE Code On Duramax? What are the indications that let you know it’s a trouble code?

Some particular symptoms indicate there might be an issue with this error code. Fine, we are now going to point out some of the following symptoms that you may notice:

  • Weaken system warning messages
  • Exaggerated black  smoke
  • Low performance of the engine
  • Reduced fuel efficiency
  • Check engine light gets active
  • Missing PDF regeneration

Overall, these are the common dysfunctions that you may notice in the OBD.

Pro Tips: P20EE code definition might vary considering the manufacturer of a car. Therefore, you should contact the exact repair manual for getting the perfect code definition.

How Much Does it Cost to Fix Duramax P20EE Code?

The cost will differ depending on the type of defects there are in your Duramax. 

If the case is on NOX Sensor and you have replaced it, you will need something around  $750. And DEF fluid replacement will need $10-$30. Mainly these are the costs. Plus, you may also have to expense other tasks like wire replacement or emission leakage repairing.

Can you drive your Duramax with a P20EE code?

The answer is yes in one word. And you have to disconnect the Duramax battery if you want to clear the trouble code.

Plus, you can replace the DEF fluid from any local store. It is recommended to fix the issue as soon as possible and then get back to driving.


At the end of the article, we hope you have got all your questions answered thoroughly. As the trouble code P20EE brings some specific problem on the Duramax engine, you have to solve it accordingly.

Firstly, find out where exactly the source of the issue is. Then, follow our procedures carefully. Once diagnosed with the problem, you are suggested to go for a solution. If it seems tough, you may take your Duramax to a professional service.

Another aspect you should keep in mind is that there are various solutions for several issues. That means you have to be more cautious about this issue.

Similar Posts