Komatsu D31EX-21 KOMSTAT II to D39PXI-23 specifications

KOMSTAT II is a control revision within the dash-21 family

Komatsu's development report distinguishes the original hydraulically controlled D31/37/39-21 hydrostatic system from the later electronically controlled servo arrangement. The revised controller uses engine speed, hydrostatic load pressure and lever input to determine pump displacement. A dash-21 model number alone does not identify which control arrangement a service enquiry concerns.

The upgrade also separates continuously adjustable travel speed from quick-shift mode, which provides familiar stepped selections. Reverse-speed presetting changes the relationship between forward and reverse travel. Describe those settings when comparing cycle behavior; an intentionally different reverse speed is not evidence of slipping drive.

The report describes progressive brake-pedal operation: initial pedal travel reduces hydraulic pump capacity, with further travel applying the mechanical brake. Its electrical redundancy and displayed errors are part of that specific system. Do not import an older hydraulic-joystick adjustment procedure into an electronically controlled machine without checking the applicable manual.

D39PXi-23 adds blade automation beyond travel control

The D39i-23 manufacturer brochure describes an integrated GNSS antenna on the cab, an enhanced inertial measurement unit and stroke-sensing hydraulic cylinders. These form the machine-control package; an antenna by itself does not establish that the full system is present or functioning on a used machine.

Its automatic dozing adjusts blade elevation in response to load, with selectable operating modes and load settings for the material. Those blade functions answer a different question from the earlier KOMSTAT travel-speed selections. Record whether an observed change concerns blade automation, traction or the operator's travel setting.

The D39i-23 pedal can operate in decelerator mode or brake mode. In the latter, travel slows while engine speed remains high to support work-equipment response. A high engine speed while slowing is therefore not automatically a failed decelerator.

This brochure covers the Tier 4 Interim dash-23 generation. It does not establish the later dash-24's equipment or retrofit capability. The earlier D31/D37 machines and non-intelligent D39 records below remain separate configurations, with all their original figures retained.