YANMAR-P20EE serious Yanmar ›

SCR NOx Catalyst Efficiency Below Threshold

The YANMAR-P20EE (Yanmar) diesel fault code means: SCR NOx Catalyst Efficiency Below Threshold. This is a serious severity code.

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Keep driving?
Limited driving only
DIY difficulty
advanced
Estimated cost
$300-$3,500

What Are the Symptoms of YANMAR-P20EE?

  • 3-stage derate countdown, DEF lamp

What Causes YANMAR-P20EE? (Most Likely First)

  • Contaminated DEF fluid Likely
  • Failed downstream NOx sensor Likely
  • Aged SCR catalyst Possible

Can I Still Drive with YANMAR-P20EE?

Limited driving only. YANMAR-P20EE is rated serious severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.

Frequently Asked Questions

What is Yanmar code P20EE?

Yanmar P20EE: SCR NOx Catalyst Efficiency Below Threshold. This code is reported on Yanmar equipment running the described engine family.

Can I keep working with Yanmar code P20EE?

Limited operation only -- finish the current task then shut down for repair.

How much does Yanmar P20EE cost to fix?

Estimated repair cost: $300-$3,500. Off-road diesel shop labor runs $125-$175/hr in 2026. Dealer diagnostic software (Yanmar SmartAssist / YDT) is usually required.

Mechanics Guide Step-by-step diagnosis

How Do You Diagnose YANMAR-P20EE?

  1. Test DEF with refractometer (32.5%).

  2. Scan both NOx sensors under load.

  3. Check SCR dosing rate.

Sources 1

This page is built from documented references. Verify against your own service info before repair work.

  • SAE J2012Diagnostic Trouble Code Definitions (defines P20EE as a generic OBD-II code)

P20EE on Other Platforms

The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown:

Bobcat serious SCR NOx Catalyst Efficiency Below Threshold (Bank 1) Duramax critical SCR NOx Catalyst Efficiency Below Threshold Bank 1 Hino serious SCR NOx Catalyst Efficiency Below Threshold Bank 1 Isuzu serious SCR NOx Catalyst Efficiency Below Threshold Bank 1 Kubota serious SCR NOx Catalyst Efficiency Below Threshold - Bank 1 Power Stroke serious SCR NOx Catalyst Efficiency Below Threshold Bank 1

Which Vehicles Commonly Get YANMAR-P20EE?

  • Yanmar SA221 / SA324 / SA424 compact tractors
  • Yanmar YT235 / YT347 / YT359 compact tractors
  • Yanmar LX4100 / LX4900 utility tractors
  • Yanmar ViO17 / ViO25 / ViO35 / ViO45 / ViO55 / ViO80 mini excavators
  • Yanmar B27-3 / B37-3 / B50-3 compact excavators
  • Cub Cadet Yanmar Ex3200 / Lx410 compact tractors (rebadged)
  • John Deere 17G / 26G / 35G compact excavators (Yanmar powered)
  • Takeuchi TB210R / TB216 / TB230 mini excavators (Yanmar powered)

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