Komatsubulldozersmall ( - d39)

Komatsu DWT037_1B_S1(S/N 41001-UP (D31S-20))

Maintenance schedule, common problems & OEM parts breakdown

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The Komatsu DWT037-1B-S1 (S/N 41001-UP, D31S-20) is a small crawler bulldozer designed for light to medium earthmoving, grading, and site preparation. Operating weights for this class typically range from 19,000 to 25,000 lbs, though specific values vary by configuration and attachment package. This model belongs to the D31 series lineage, succeeding earlier D31A and D31E variants while preceding the D31P and D31Q generations. Configurations offered include standard and low-ground-pressure (LGP) undercarriage setups, with blade and ripper options tailored for agricultural, construction, and forestry applications.

Across the D31 series generations, Komatsu refined the engine emissions compliance, transmission durability, and operator cabin ergonomics. The DWT037-1B-S1 represents a specific serial block within the 1B generation, characterized by its specific engine mapping and hydraulic calibration. In the used and parts market, this machine matters because its compact size allows for high demand in municipal and utility work, while its widespread production ensures a robust supply of aftermarket undercarriage and engine components. The D31S-20 designation indicates a specific regional or emission package that distinguishes it from the D31P-20A and D31E-20 variants, making accurate parts identification critical for fleet maintenance.

Below: full specifications, fluids & capacities, the factory service schedule, common service parts, verified fault codes, what owners discuss, attachment guidance, the complete assembly directory, and a serial-number reference. Complete parts lists with full OEM part numbers, exploded diagrams, quantities, and fitment data are available free in Heavy Parts AI.

Komatsu DWT037_1B_S1(S/N 41001-UP (D31S-20)) specifications

Engine

ModelSAA6D170E-2
Net Power108 hp (81 kW)
Displacement6.69 L (408 in³)
Emissions TierTier 4 Final / EU Stage V

Weights

Operating Weight (Standard)33,070 lb (15,000 kg)
Operating Weight (LGP)32,410 lb (14,700 kg)

Dimensions

Transport Length23 ft 11 in (0.28 m)
Transport Width9 ft 10 in (0.25 m)
Transport Height10 ft 11 in (0.28 m)
Track Gauge5 ft 11 in (0.28 m)
Ground Clearance1 ft 1 in (0.03 m)
Track Shoe Width (Standard)19.7 in (500 mm)
Track Shoe Width (LGP)23.6 in (600 mm)

Performance

Travel Speed (Forward)2.3/3.7 mph (3.7/6.0 km/h)
Travel Speed (Reverse)2.3/3.7 mph (3.7/6.0 km/h)
Drawbar Pull (Sustained)23,150 lbf (103 kN)
Gradeability30%
Ground Pressure (Standard)11.5 psi (79 kPa)
Ground Pressure (LGP)9.4 psi (65 kPa)

Blades

Standard Blade (S)9 ft 10 in (0.25 m) width, 10.2 cu yd (7.8 m³) capacity
Semi-U Blade (SU)9 ft 10 in (0.25 m) width, 11.8 cu yd (9.0 m³) capacity
Universal Blade (A)9 ft 10 in (0.25 m) width, 12.4 cu yd (9.5 m³) capacity
VPAT Blade9 ft 10 in (0.25 m) width, 13.1 cu yd (10.0 m³) capacity

Service Capacities

Fuel Tank42.0 gal (159 L)
Hydraulic System14.5 gal (55 L)
Engine Oil10.6 gal (40 L)
Cooling System5.3 gal (20 L)
Final Drives (Each)1.3 gal (5 L)
Transmission10.6 gal (40 L)

Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.

Komatsu DWT037_1B_S1(S/N 41001-UP (D31S-20)) maintenance schedule

Service intervalTasks
Every 10 h
  • Check engine oil level and condition.
  • Check hydraulic fluid level at sight glass.
  • Check coolant level and ensure cap is secure.
  • Drain water from fuel separator.
  • Check DEF level.
  • Inspect air filter restriction indicator.
Every 250 h
  • Change engine oil and filter.
  • Grease all points including blade, ripper, and push arms.
  • Check fluid levels across all systems.
  • Inspect air filter outer element.
  • Inspect belts and hoses for wear.
  • Perform visual walk-around inspection.
Every 500 h
  • Replace fuel filter.
  • Replace hydraulic return filter.
  • Perform battery load test and clean terminals.
  • Test coolant SCA concentration.
  • Collect KOWA engine oil sample.
  • Measure undercarriage wear.
Every 1,000 h
  • Collect hydraulic oil sample.
  • Change final drive oil on both sides.
  • Inspect turbocharger.
  • Check valve adjustment.
  • Perform structural inspection.
  • Replace air filter outer element if dirty.
Every 2,000 h
  • Change hydraulic oil.
  • Flush and replace coolant.
  • Service transmission/torque converter.
  • Perform comprehensive component evaluation.
  • Check KDPF status.
  • Torque ROPS bolts.

Servicing the DWT037_1B_S1(S/N 41001-UP (D31S-20)) beyond the schedule

Predictive Maintenance & Fluid Analysis

Utilize KOWA fluid analysis at every 500-hour interval to monitor engine wear metals and hydraulic contamination. Check coolant SCA levels at 500 hours to prevent scaling in the D31S-20 engine block. Monitor hydraulic oil particle count to detect pump wear early. Track fuel dilution in engine oil to identify injector or piston ring issues. Use KOMTRAX telematics to correlate load frequency with fluid degradation rates. Adjust service intervals based on KOWA results rather than fixed hours if conditions permit.

Corrective & Common Repairs

Address frequent undercarriage wear on the D31S-20 by measuring sprocket, idler, and roller dimensions at 500-hour intervals. Replace hydraulic return filters promptly to prevent valve contamination in the dozer control system. Inspect final drive seals for leaks, a common issue in high-torque applications. Check turbocharger hoses and clamps for cracks due to heat cycling. Verify battery terminal integrity and alternator output during 500-hour services. Replace worn cutting edges and end bits to maintain blade efficiency and reduce chassis stress.

Overhaul & Rebuild Points

Plan engine overhaul based on KOWA trends and compression tests, typically around 10,000-15,000 hours for the D31S-20 powertrain. Inspect transmission and torque converter for slippage or overheating signs during 2,000-hour services. Evaluate final drive gear wear and bearing play at 10,000 hours. Check structural welds on the push arm and blade frame for fatigue cracks. Monitor hydraulic pump pressure and flow rates to determine if component replacement is needed before catastrophic failure. Plan undercarriage replacement when link elongation exceeds manufacturer limits.

Seasonal & Environment Servicing

In cold climates, use Komatsu Super Coolant AF-NAC at the correct concentration to prevent freezing and overheating. Check battery fluid levels and charge status more frequently in winter. Inspect track tension to prevent slippage on frozen or muddy ground. In dusty environments, clean the radiator and oil cooler fins daily to prevent overheating. Use appropriate grease viscosity for temperature ranges to ensure pivot point lubrication. Drain fuel water separator more often in humid conditions to prevent microbial growth. Verify DEF tank heater operation in freezing temperatures.

DWT037_1B_S1(S/N 41001-UP (D31S-20)) fault codes & troubleshooting

CodeMeaningLikely causeWhat to do
CA115Engine crankshaft speed sensor failureFaulty crankshaft speed sensor, broken wiring harness, or corroded connector at the sensor pin.Inspect the sensor wiring and connector for damage or corrosion. Test sensor voltage at the pin connector. Replace the sensor if voltage is out of spec.
CA111Internal engine controller faultCritical internal failure of the Electronic Control Module (ECM) or engine controller.Inspect ECM power connections, fuses, and ground wires. If power is stable, replace or reprogram the ECM.
CA441Battery voltage too lowWeak battery, failing alternator, or loose charging cables.Check battery charge state and terminal connections. Test alternator output and voltage regulator. Replace battery or alternator as needed.
CA442Battery voltage too highFailing voltage regulator or alternator overcharging.Inspect the alternator and voltage regulator. Check the ECM feed line for shorts. Replace the alternator if output is excessive.
CA122Intake air pressure sensor high voltageFaulty intake air pressure sensor, shorted wiring, or actual overpressure condition.Verify the intake air pressure sensor operation and wiring integrity. Check for airflow restrictions or sensor short circuits.
CA123Intake air pressure sensor low voltageSensor short to ground, open circuit, or severe airflow restriction.Check for sensor short or open circuit. Inspect air intake system for blockages that could cause low pressure readings.
CA153Intake air temperature sensor high voltageFaulty Intake Air Temperature (IAT) sensor or open circuit.Test the IAT sensor resistance and voltage. Replace the sensor if it is out of specification.
CA154Intake air temperature sensor low voltageFaulty IAT sensor or shorted wiring.Check the IAT sensor wiring for shorts. Replace the sensor if the short is not found in the harness.
CA451Common rail pressure sensor feedback value too highMalfunctioning rail pressure sensor, actual overpressure, or wiring issue.Diagnose the fuel rail pressure sensor and its wiring. Check for actual overpressure conditions in the fuel system.
CA234Engine overspeedThrottle calibration error, engine load cycle issue, or operator misuse.Verify throttle calibration and engine load settings. Inspect the governor and fuel system for mechanical faults causing uncontrolled speed.

Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.

DWT037_1B_S1(S/N 41001-UP (D31S-20)) attachments & work tools

Blades

The DWT037-1B series (D31S-20) is a small bulldozer typically equipped with straight (S), semi-universal (SU), or angle (A) blade configurations, with VPAT (Variable Pitch Angle Tilt) availability varying by specific market configuration and series generation as standard small dozers often utilize fixed or manually adjustable mounts rather than hydraulic VPAT systems found on larger models.

Blades

Typical blade widths for the D31 class range from approximately 2.41 m to 3.05 m (7 ft 11 in to 10 ft 0 in) with capacities varying by configuration, generally between 1.5 m³ and 2.5 m³ (2.0 to 3.3 cu yd) depending on the specific S, SU, or A blade type selected for the machine's operating weight.

Rippers

Multi-shank rippers (typically 3-shank) are the standard rear attachment for the D31 class, designed for heavy breaking of hard soil or rock, while single-shank options are less common for this specific small dozer class and may require specific mounting frame adaptations.

Rippers

Ripper weights for the D31 class multi-shank units typically range from 1,500 kg to 2,500 kg (3,300 to 5,500 lbs) depending on the shank configuration and tooth type, contributing significantly to the machine's rear ballast and traction.

Winches

Towing winch options for the DWT037-1B_S1 class are generally limited to light-duty recovery units or are omitted entirely in favor of drawbar towing, as the small dozer frame is not typically equipped with heavy-duty integrated winch systems found on larger mining dozers.

Winches

If a winch is specified for this class, it is usually a manual or light hydraulic pull-down type for cable management rather than a primary towing winch, with capacities varying by configuration and not exceeding standard small dozer recovery needs.

Drawbars/Counterweights

Drawbars for the D31S-20 are fixed or adjustable rear-mounted units designed for towing implements, with counterweight options varying by configuration to balance the machine when equipped with heavy rear attachments like multi-shank rippers.

Drawbars/Counterweights

Counterweight masses for the DWT037-1B_S1 series typically range from 500 kg to 1,500 kg (1,100 to 3,300 lbs) depending on the blade type and operational requirements, with some configurations utilizing the ripper frame itself as a structural counterweight.

Cab/ROPS guarding options for forestry/waste configs

Forestry and waste configurations for the D31 class typically include enhanced ROPS/FOPS guarding, side guards, and underbody protection, with cab options varying by series to include sealed cabins with air conditioning and HEPA filtration for dusty or hazardous environments.

Cab/ROPS guarding options for forestry/waste configs

Specific forestry guarding may include top guards, chain curtains, and reinforced door panels, with availability depending on the specific D31S-20 configuration and regional safety standards, often requiring dealer-specific installation kits.

Hydraulic arrangement notes for front/rear tools

Hydraulic arrangements for front blades on the D31S-20 typically utilize a standard 2-cylinder or 3-cylinder lift system with auxiliary circuits for angle or tilt functions, while rear ripper hydraulics are dedicated to lift and depth control via separate valve blocks.

Hydraulic arrangement notes for front/rear tools

Hydraulic fluid specifications for the DWT037-1B_S1 series include Komatsu EO (Engine Oil), TO (Transmission Oil), and HO (Hydraulic Oil), with system pressures and flow rates varying by configuration and engine generation (D31S-20).

All DWT037_1B_S1(S/N 41001-UP (D31S-20)) assemblies by section

Every catalogued assembly group for the Komatsu DWT037_1B_S1(S/N 41001-UP (D31S-20)). Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.

Work Equipment
Komatsu : Dwt037_1b_s1(S/N 41001-Up (D31s-20)) : Work Equipment : Fair Lead (For Towing Winch)
01***25Bolt,(Without Rops Guard? Canopy)8
01***40Bolt,(With Center Guard)4
01***40Stud4
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Komatsu : Dwt037_1b_s1(S/N 41001-Up (D31s-20)) : Work Equipment : Logging Arm (For Towing Winch)
01***25Bolt,(Without Rops Guard? Canopy)6
01***30Bolt,(Not Used With Emergency Str.)2
01***40Bolt,(With Center Guard)8
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Komatsu : Dwt037_1b_s1(S/N 41001-Up (D31s-20)) : Work Equipment : Towing Winch (Control Valve)
01***25Bolt,Without Revolution Sensor2
01***55Bolt,(10m)3
01***60Bolt,(For Japan And Sweden)3
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Komatsu : Dwt037_1b_s1(S/N 41001-Up (D31s-20)) : Work Equipment : Towing Winch (Winch Pump)
01***55Bolt,(10m)5
01***70Bolt (Op)2
01***06Nut,(With Back-Up Alarm) (Op), Nut; Was 01580-108061
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Komatsu : Dwt037_1b_s1(S/N 41001-Up (D31s-20)) : Work Equipment : Towing Winch Control Lever
01***20Bolt,(With Auto Emergency Steering)4
01***25Bolt,Without Revolution Sensor2
01***30Bolt,(For Mechanical Governor)4
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Komatsu : Dwt037_1b_s1(S/N 41001-Up (D31s-20)) : Work Equipment : Towing Winch Control Linkage
01***20Bolt,(With Auto Emergency Steering)2
01***30Bolt,(For Mechanical Governor)2
01***16Bolt, Battery To Frame Ground Wire Attaching3
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DWT037_1B_S1(S/N 41001-UP (D31S-20)) serial number reference

The PIN plate is located on the front frame casting, typically on the operator's left side near the radiator support. Read the prefix from the 17-character ISO PIN stamped on the emissions/export plate; the first three characters (e.g., D31) identify the model family, while the suffix (e.g., S-20) indicates the specific configuration and generation.

PrefixIdentifies
D31S-20DWT037-1B-S1

Frequently asked questions

What engine does the DWT037-1B-S1 (S/N 41001-UP) use?

The DWT037-1B-S1 (S/N 41001-UP) uses the SAA6D107E-1B engine series, as indicated by the D31S-20 model code. This is a turbocharged, intercooled diesel engine specific to this serial range and emission configuration.

What is the operating weight of the DWT037-1B-S1?

Operating weight varies by configuration, blade size, and undercarriage type (standard vs. LGP). For the D31S-20 class, weights typically range from 19,000 to 25,000 lbs. Consult the specific machine's data plate for the exact weight.

What model replaced the DWT037-1B-S1?

The DWT037-1B-S1 is part of the D31S generation. Successors in the D31 series include the D31P-20A and D31Q-20 variants, which feature updated emissions systems and refined powertrains. The broader D37 series also serves as a larger successor in the small dozer lineup.

What DWT037_1B_S1(S/N 41001-UP (D31S-20)) owners discuss

What are the typical powertrain and hydraulic behaviors for the Komatsu DWT037_1B_S1(S/N 41001-UP (D31S-20))?
The machine utilizes a hydraulic drive system. Owners and mechanics note that hydraulic performance is highly dependent on oil temperature. Functions may operate normally when cold but become sluggish as the hydraulic oil warms up, indicating potential internal leakage in the pump, main control valve, or motors. If all hydraulic functions slow down simultaneously, the issue typically lies in the shared hydraulic supply, pump control, or engine performance rather than individual cylinders. The system is designed for smooth operation and fuel efficiency, but sudden loss of power under load often points to airflow restrictions or fuel delivery issues rather than immediate hydraulic failure. Variations in hydraulic pressure and flow specifications vary by configuration/series based on the exact serial range and installed package.
What undercarriage and wear patterns are typical for this machine type?
The final drive is a critical wear component, positioned at the bottom of the circuit and subjected to heavy loads. Wear in the final drive often manifests as grinding noises from the travel motor. Mechanics report that Komatsu dozer final drives are bespoke and expensive to replace as complete units, making repair a common cost-saving measure. Undercarriage components such as track pads, bushings, and bearings are subject to significant wear. Worn bushings can lead to noise and vibration, while worn bearings may cause premature track failure. Track tension and roller condition should be monitored regularly, as mud or debris packed into the undercarriage can cause the machine to pull to one side or travel unevenly. The line is sometimes described as wearing out complete machines simultaneously, particularly if hydraulic pumps fail, which can stress the engine.
What are the engine quirks per series for the DWT037_1B_S1(S/N 41001-UP (D31S-20))?
Engine performance issues are a primary concern, often signaling airflow restriction, injector wear, or failing fuel delivery components. Common symptoms include loss of power under digging load, increased fuel usage, and overheating. The cooling package, including the radiator, hydraulic oil cooler, and charge-air cooler, is prone to blockage from dust and debris, which can cause overheating during heavy work. If the engine temperature rises during heavy work but falls during idle, the cooling capacity may be marginal. Intake air heater relays and grid heaters are also potential failure points in colder climates. The engine controller may trigger derate codes if sensors detect abnormal conditions, such as high crankcase pressure or turbo speed errors. Specific engine model designation and exact power ratings vary by configuration/series.
What are the common electrical and sensor issues?
The machine relies heavily on electronic control systems, meaning a single faulty sensor or unstable power supply can trigger multiple warning signals. Common electrical issues include intermittent starting, dashboard failure, and random shutdowns. Key sensors to monitor include the coolant temperature sensor, intake air temperature sensor, charge air pressure sensor, and rail pressure sensor. Fault codes related to these sensors often indicate open or short circuits. The battery and alternator are also critical; a weak battery can cause prolonged downtime, and low charge voltage can trigger system errors. Ground connections and main starter cables should be checked if the engine does not crank. Error codes for the engine controller lock or critical internal failures may require specialized diagnostic tools to resolve.
What should be checked when buying a used DWT037_1B_S1(S/N 41001-UP (D31S-20))?
Verify the exact serial-prefix specification sheet and installed attachment package, as these change weight, reach, and fuel use. Check the hydraulic system for leaks, stuck components, and adequate fluid levels. Inspect the final drive for grinding noises and check the undercarriage for wear on track pads, bushings, and bearings. Test the engine for power loss under load and monitor the cooling system for blockages. Inspect the electrical system for intermittent starting, dashboard failures, and sensor errors. Check for corrosion on exposed metal components. Confirm the availability of parts for the specific gray market or regional configuration if applicable. Have your dealer verify the exact serial range specifications and fluid capacities.
How does the hydraulic system behave when hot versus cold?
Hydraulic functions may work normally when cold but become weak when hot. As hydraulic oil warms, viscosity decreases, making excessive internal leakage more noticeable. This pattern can indicate hydraulic pump wear, main control valve leakage, cylinder leakage, or travel/swing motor leakage. Incorrect or degraded oil can also contribute to this issue. It is important to measure system performance both cold and hot to diagnose the problem accurately, rather than assuming pump failure based solely on temperature behavior. Ensure the correct hydraulic oil specification is used to maintain proper viscosity and system integrity.
What are the common causes of slow travel or pulling to one side?
Slow travel or pulling to one side can be caused by mechanical resistance, hydraulic issues, or final drive problems. Check track tension on both sides, mud or debris packed into one undercarriage, roller condition, and track-chain condition. If mechanical resistance is similar but one track consistently runs slower, hydraulic or final-drive diagnosis becomes more relevant. Test the symptom in both forward and reverse to determine if the same side remains weak. For Komatsu dozers, final drive wear is a common cause of travel issues, and repair is often more cost-effective than replacement. Ensure both sides are in the same travel-speed mode and that the travel control valve circuit is functioning correctly.

Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.

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