YANMAR-U0101 serious Yanmar ›

Lost Communication with Transmission / Hydrostat Controller

The YANMAR-U0101 (Yanmar) diesel fault code means: Lost Communication with Transmission / Hydrostat Controller. This is a serious severity code.

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DIY difficulty
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Estimated cost
$100-$1,200
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Common Symptoms

  • Transmission won't shift on YT tractor

Probable Causes (Ranked by Likelihood)

  • CAN fault TCU <-> ECU Likely
  • Loose TCU connector Possible

Frequently Asked Questions

What is Yanmar code U0101?

Yanmar U0101: Lost Communication with Transmission / Hydrostat Controller. This code is reported on Yanmar equipment running the described engine family.

Can I keep working with Yanmar code U0101?

Do not continue operating. Risk of engine damage or unsafe shutdown.

How much does Yanmar U0101 cost to fix?

Estimated repair cost: $100-$1,200. 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

Step-by-Step Diagnostic Procedure

  1. Inspect TCU connector.

  2. Measure CAN continuity to TCU.

U0101 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 U0101 Bobcat serious Lost Communication with Transmission Control Module (Hydrostatic) Duramax serious Lost Communication with TCM Hino serious Lost Communication with TCM Isuzu serious Lost Communication with TCM (Aisin / GM trans) Kubota serious Lost Communication with TCM MaxxForce moderate Lost Communication with TCM PACCAR serious Lost Communication with TCM

Commonly Affected Vehicles

  • 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)

Related Codes

YANMAR-U0100

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