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P20EE - SCR NOx Catalyst Efficiency Below Threshold (Bank 1)

What a P20EE Code Means and How to Fix It

Today’s diesel trucks use selective catalytic reduction (SCR) to reduce nitrogen oxide (NOx) emissions, ensuring consistent adherence to emission requirements. If something goes wrong, your vehicle dashboard will show an indicator light, which may indicate a severe problem.

Prompt diagnosis and repair are essential for avoiding problems like limp mode, vehicle breakdown or emission-related fines. Technicians and car owners use onboard diagnostics (OBD) II scanners to diagnose problems. However, the scanner gives you the solution in code form. What does it mean when you get the code P20EE from the OBD scanner? Let’s take a look.

What Is the P20EE Code?

It’s equivalent to the error message “SCR NOx catalyst efficiency below threshold.” The SCR system isn’t removing sufficient emissions, and emission levels have risen above acceptable standards.

This common problem for diesel vehicle owners is often a secondary symptom of a more noteworthy SCR challenge.

 

Symptoms of a P20EE Code

If your catalyst efficiency drops below the threshold, you may experience the following:

  • Check engine light/dash indicator: The P20EE code and check engine light often occur together. The root cause usually triggers both occurrences.
  • DEF or SCR warning lights: This code is often accompanied by similar SCR or DEF codes like P20EC, P20ED and P20EF. 
  • Reduced engine power/limp mode: This DEF system fault code may cause a reduction in engine power. If you don’t solve the problem promptly, your vehicle may enter limp mode due to P20EE-related issues.
  • Increased fuel consumption/decreased mileage: The root cause of the P20EE code often decreases fuel consumption and makes your vehicle work harder to achieve the same result.
  • Excessive smoke production: Emissions increase when your SCR system malfunctions, and the vehicle produces excessive black smoke. 

These are just a few common symptoms, but you may encounter others, depending on what caused the code.

 

Common Causes of P20EE

The P20EE code is a broad error classification since it covers anything that inhibits or prevents appropriate emission management. Some common causes of the P20EE code include:

Insufficient Fluid

When your DEF tank contains insufficient fluid, it can lead to various problems. The SCR sprays fluid into the exhaust stream, where it reacts with nitrogen oxides, converting them to hydrogen gas and water vapor. Since DEF is integral to reducing emissions, insufficient fluid causes an increase in emissions. 

Low-Quality Diesel Engine Fluid

Low-quality DEF may cause SCR issues. Some products are prone to evaporation and degradation, which causes crystallization within the system. From clogging pipes and nozzles to reducing system efficiency, crystallization due to low-grade fluid is a serious problem. 

Even premium-grade DEF may degrade under certain conditions, resulting in similar problems. Common causes of DEF degradation include:

  • Exposure to high temperatures
  • Incorrect storage leading to evaporation
  • Contamination with dust, rust and other debris

DEF Deposits or Crystallization

As mentioned above, DEF can crystallize, causing deposits and crystallization. The fluid consists of a blend of liquid urea and water. When the water evaporates, the urea becomes more concentrated, leading to crystallization. 

This kind of deposit can devastate the system, affecting everything from spray patterns to sensor function.

Faulty Injectors

Fluid injectors are integral to the SCR system’s success. If they malfunction or lack the correct spray pattern, they’re ineffective against nitrogen oxides. A fine spray pattern is essential for converting as many emissions as possible. However, due to wear, clogging and other causes, injectors may fail and increase emissions.

Sensor Malfunction

SCR sensors malfunction due to electrical faults, crystal buildup or other faults. When they malfunction and do not detect emissions as they should, a P20EE code can occur. Crystal buildup is easy to solve. However, electrical and other issues will require professional intervention.

System Leaks

System leaks in the exhaust, SCR or DEF systems can cause significant emission problems. Leaks in the SCR or DEF system prevent fluid from going to the right places, interrupting emission management and failing to ensure compliance.

Leaks in the exhaust system mean fumes can circumvent the SCR system, compromising its effectiveness. 

 

How to Clear a P20EE Code

Let’s discuss how to fix a diesel P20EE fault code. It should be easy to repair if the problem results from low-quality DEF or crystal buildup. However, if contamination or a more complex issue is at fault, you’ll need professional help from a technician.

Clear up crystallization-related issues with a quality additive like Premium DEFender™. Refill your DEF tank with high-quality diesel exhaust fluid, ensuring you add an ounce of Premium DEFender for every 2.5 gallons of fluid. Then, run the engine steadily for at least 30 minutes, driving slowly and constantly. It might take a tank of treated fluid to clear the code

The additive dissolves urea buildup systemwide, restoring flow and eliminating blockages. The new DEF and Premium DEFender will clear the error code if there is insufficient fluid or crystallization. If not, take your vehicle for a professional diagnostic.

 

How Premium DEFender™ Helps Avoid the P20EE Code

Premium DEFender prevents many common DEF and SCR problems by:

  • Improving fluid lubricity to minimize abrasion
  • Dissolving urea crystals before they form deposits
  • Lowering the DEF freeze point to protect the fluid
  • Restoring nozzle spray patterns

 

FAQs About the P20EE Code

Review details about the P20EE code with these FAQs.

Is it safe to drive with a P20EE code?

No, driving with a P20EE code isn’t safe — you can do so for a while, but we don’t recommend it. The code indicates a problem with the selective catalytic reduction (SCR) system, and continued driving may lead to additional damage. 

Can a P20EE code clear on its own?

No, you cannot rely on a P20EE code to clear spontaneously. It indicates an underlying issue with the SCR system and will likely recur. However, if you have refilled the DEF tank or started using a premium additive, the P20EE code may clear.

How much does it cost to repair a P20EE code?

Diverse potential underlying causes make the amount impossible to pinpoint. Solving crystal buildup is cost-effective, but repairing or replacing a faulty injector or sensor may be more expensive. Expect to pay between $100 for a minor fix and over $1,000 for more severe repairs.

Can additives prevent the P20EE code from returning?

If the P20EE code results from crystal buildup, a premium additive like Premium DEFender can prevent recurring problems. However, an additive can’t avoid the recurrence of electric faults or similar challenges.

 

Resolve P20EE Codes With Hot Shot’s Secret

While more severe problems may occur, the most common DEF system fault codes are caused by simple issues like crystallization. Eliminate many standard fault codes with a high-quality additive like Premium DEFender. Our high-quality solution eliminates crystallization, improves lubricity and more!