YANMAR-P0401 moderate Yanmar ›

EGR Insufficient Flow Detected

The YANMAR-P0401 (Yanmar) diesel fault code means: EGR Insufficient Flow Detected. This is a moderate severity code.

My Garage →
Keep driving?
Yes, but fix soon
DIY difficulty
intermediate
Estimated cost
$0-$800

What Are the Symptoms of YANMAR-P0401?

  • Slight derate, regen frequency up

What Causes YANMAR-P0401? (Most Likely First)

  • Sooted EGR valve Very Likely
  • Plugged EGR cooler on Tier 4F Yanmar Likely

Can I Still Drive with YANMAR-P0401?

Yes, but fix soon. YANMAR-P0401 is rated moderate severity. It is not an immediate stop-driving fault, but it will not clear itself — book the repair rather than ignoring it.

Frequently Asked Questions

What is Yanmar code P0401?

Yanmar P0401: EGR Insufficient Flow Detected. This code is reported on Yanmar equipment running the described engine family.

Can I keep working with Yanmar code P0401?

Usually drivable short-term, but fix soon to avoid derate or DPF issues.

How much does Yanmar P0401 cost to fix?

Estimated repair cost: $0-$800. 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-P0401?

  1. Command EGR sweep in SmartAssist.

  2. Clean EGR valve; force regen.

Sources 1

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

  • SAE J2012Diagnostic Trouble Code Definitions (defines P0401 as a generic OBD-II code)

P0401 on Other Platforms

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

Gas / Automotive (OBD-II) Generic OBD-II definition for P0401 Bobcat moderate EGR Insufficient Flow Detected Duramax moderate Exhaust Gas Recirculation Flow Insufficient Detected Hino moderate EGR Flow Insufficient Isuzu moderate EGR Flow Insufficient Kubota moderate EGR Flow - Insufficient PACCAR moderate EGR Flow Insufficient Power Stroke moderate Exhaust Gas Recirculation Flow Insufficient

Which Vehicles Commonly Get YANMAR-P0401?

  • 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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