Diagnostic Trouble Code P20EE: SCR NOx Catalyst Efficiency Below Threshold 

With rising concern of environment pollution, complex systems are equipped in modern cars to reduce emission. One such system is the Selective Catalytic Reduction (SCR) system. If you're seeing Error Code P20EE, it's a sign that the SCR system isn't operating as intended.

What does DTC P20EE means? 

The SCR system plays a crucial role in reducing nitrogen oxide (NOx) emissions by injecting (DEF) Diesel Exhaust Fluid (This fluid is commonly known by the brand name AdBlue) into the exhaust stream. This process transforms harmful NOx into harmless nitrogen and water vapor. The Powertrain Control Module (PCM) monitors the efficiency of this system through various sensors. When it detects that the SCR NOx catalyst isn't performing as expected, it triggers the P20EE code.

Symptoms of Error Code P20EE 

Check Engine Light will be illuminated 

DEF warning light / Service System message will be displayed

Vehicle will go to Limp mode – limiting speed and power to prevent further issues

Increased emissions

Poor fuel efficiency

Causes for P20EE Error Code

Low quality or contaminated Diesel Exhaust Fluid can impair SCR catalyst’s ability to reduce NOx emissions

Faulty NOx sensors will provide inaccurate data to Control Modules which leads to improper DEF injection reducing catalyst efficiency.

A clogged or malfunctioning DEF injector can prevent the proper dosing of DEF into the exhaust stream.

Leaks in exhaust system will introduce unmetered air and it will affect sensor reading which will eventually affect catalyst performance

With time, the SCR catalyst can become clogged due to soot buildup or contamination, leading to decreased efficiency.

Incorrect software programming can also cause SCR system inefficiency.

Preventive Measures for P20EE

Use good quality Diesel Exhaust Fluid for better efficiency

Adhere to manufacturer recommended maintenance schedule

Monitor DEF: check whether it is expired, whether it is contaminated, whether it is upto correct level

Address SCR related issues promptly. 
 
The P20EE code is a serious indication that your vehicle's SCR NOx catalyst isn't operating efficiently. Prompt diagnosis and repair are crucial to restore your vehicle's emissions system to proper functioning and to avoid potential damage or increased emissions. Regular maintenance and attention to the quality of DEF can help prevent this issue from arising. If you're experiencing the P20EE code, contact us to accurately diagnose and address the underlying cause. 

Checkout our latest Video on P20EE

Frequently Asked Questions

Can I drive my vehicle with a P20EE code?

You can drive but it is not recommended as the emission system isn’t functioning well. Continuous driving with P20EE code will trigger limp mode sometimes your vehicle will enter no start condition. 
You may also risk damaging costly components like the SCR catalyst or failing emissions inspections.

What is the SCR NOx catalyst and why is it important?

The Selective Catalytic Reduction (SCR) NOx catalyst is part of a diesel vehicle's emissions system. It reduces harmful nitrogen oxide (NOx) emissions by converting them into harmless nitrogen and water through a chemical reaction with Diesel Exhaust Fluid (DEF). It’s crucial for meeting environmental regulations and ensuring cleaner emissions. 

Can bad DEF fluid cause a P20EE code?

Yes. Using contaminated, expired, or non-spec DEF fluid can reduce the SCR system’s ability to convert NOx, triggering this code.  

How do I reset the P20EE code?

Simply clearing the code won’t fix the issue. Should resolve underlying cause. Some vehicle may require few driving cycles so that EMC will re-evaluate system performance and then the warning message will be turned off 
 
Is P20EE an emissions-related code for inspection failure?

Yes. P20EE is directly tied to emissions system performance. If active, it will cause your vehicle to fail an emissions test in most regions.