Komatsu 4D84E-3B(S/N 00000-UP)
Maintenance schedule, common problems & OEM parts breakdown
The Komatsu 4D84E-3B engine powers the PC50UU-2 crawler excavator, a compact machine in the 5-ton class with an operating weight of approximately 11,000 to 12,000 lb (5,000 to 5,400 kg). Produced during the PC50UU-2 generation, this engine serves as the power source for early serial range units (S/N 12772-14992) before transitioning to the 4D84E-3C variant. The PC50UU-2 configuration offers a compact radius design suitable for utility trenching and confined site work, bridging the gap between smaller mini-excavators and larger mid-size models.
Across the 4D84E series, Komatsu shifted from the 3-cylinder 3D84E to the 4-cylinder 4D84E architecture to meet evolving emissions standards and torque requirements. The 4D84E-3B is significant in the used market as the specific engine for the initial PC50UU-2 production run. Its compact footprint and proven reliability make it a common replacement target for aging units, while its distinct serial range (ending at 14992) helps buyers identify early-generation machines that may require specific parts or calibration updates compared to later 4D84E-3C or 3D variants.
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 4D84E-3B(S/N 00000-UP) specifications
Engine
| Model | 4D84E-3B |
| Application | Komatsu PC50UU-2 |
| Serial Range | 12772-14992 |
| Configuration | Vertical, water-cooled, 4-stroke, turbocharged diesel engine |
| Displacement | 2.0 L (121.8 cu. in.) |
| Cylinders | 4 |
| Bore x Stroke | 84 x 90 mm |
| Net Power | 28.3 kW (38 HP) @ 2500 rev/min |
| Emissions Tier | Not documented for this exact serial range — verify with your dealer |
Weights
| Operating Weight | Not documented for this exact serial range — verify with your dealer |
| Shipping Weight | Not documented for this exact serial range — verify with your dealer |
| Ground Pressure | Not documented for this exact serial range — verify with your dealer |
Dimensions
| Transport Length | Not documented for this exact serial range — verify with your dealer |
| Transport Width | Not documented for this exact serial range — verify with your dealer |
| Transport Height | Not documented for this exact serial range — verify with your dealer |
| Track Gauge | Not documented for this exact serial range — verify with your dealer |
| Ground Clearance | Not documented for this exact serial range — verify with your dealer |
Performance
| Travel Speed | Not documented for this exact serial range — verify with your dealer |
| Dig Depth | Not documented for this exact serial range — verify with your dealer |
| Gradeability | Not documented for this exact serial range — verify with your dealer |
Service capacities (summary)
| Fuel Tank | Not documented for this exact serial range — verify with your dealer |
| Hydraulic System | Not documented for this exact serial range — verify with your dealer |
| Engine Oil | Not documented for this exact serial range — verify with your dealer |
| Cooling System | Not documented for this exact serial range — verify with your dealer |
Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.
Komatsu 4D84E-3B(S/N 00000-UP) maintenance schedule
| Service interval | Tasks |
|---|---|
| Every 10 h |
|
| Every 250 h |
|
| Every 500 h |
|
| Every 1,000 h |
|
| Every 2,000 h |
|
Servicing the 4D84E-3B(S/N 00000-UP) 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 concentration at 500 hours to prevent liner cavitation. Monitor DEF levels daily on Tier 4 models to ensure SCR system efficiency. Track KOMTRAX telematics data for load frequency and fuel burn anomalies. Early detection of viscosity changes in hydraulic oil prevents pump wear. Regular oil sampling identifies fuel dilution before it damages the 4D84E-3B crankcase.
Corrective & Common Repairs
Address fuel filter clogging promptly to protect the 4D84E-3B injection system. Replace hydraulic return filters at 500 hours to maintain valve responsiveness. Inspect turbocharger connections for leaks during the 1000-hour service. Check belt tension and hose clamps to prevent overheating. Replace worn track rollers and idlers to maintain undercarriage alignment. Fix hydraulic hose cracks early to avoid fluid loss and component damage.
Overhaul & Rebuild Points
Plan major engine overhaul based on KOWA results and compression tests. Replace cylinder liners and piston rings when wear exceeds limits. Inspect crankshaft bearings for scoring during disassembly. Rebuild the hydraulic pump and swing motor if flow or pressure drops. Replace final drive gears and seals during the 1000-hour oil change if metal particles are present. Address structural weld cracks on the boom and stick during the 2000-hour comprehensive inspection.
Seasonal & Environment Servicing
Use low-viscosity oil in cold climates to ensure easy starting. Check coolant freeze point before winter. Drain water from the fuel separator daily in humid conditions. Clean radiator and oil cooler fins regularly to prevent overheating in dusty environments. Inspect air filter restriction indicator frequently in high-dust jobsites. Grease all pivot points more often in wet or muddy conditions to wash out contaminants.
4D84E-3B(S/N 00000-UP) common service parts
| Part number | Part | Notes | |
|---|---|---|---|
| YM129100-55650 | Element,Fuel Filter | Fuel system service | Check fitment → |
| YM129052-55620 | Fuel Filter Ass'Y | Fuel system service | Check fitment → |
| YM102103-55520 | O-Ring,(For Fuel Filter) | Fuel system service | Check fitment → |
| YM121120-12901 | Element | Scheduled service item | Check fitment → |
| YM129150-35152 | Filter Element | Scheduled service item | Check fitment → |
Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.
4D84E-3B(S/N 00000-UP) fault codes & troubleshooting
| Code | Meaning | Likely cause | What to do |
|---|---|---|---|
| CA115 | Engine crankshaft speed sensor failure | Broken sensor, wiring issue, or connector corrosion | Replace the speed sensor and verify voltage at the pin connector |
| CA111 | Internal engine controller fault | ECM hardware failure or corruption | Replace or reprogram the ECM |
| CA451 | Common rail pressure sensor feedback value too high | Malfunction in the rail sensor or actual overpressure condition | Diagnose the fuel rail pressure sensor or pump lines |
| CA452 | Common rail pressure sensor feedback value too low | Sensor failure, air in fuel lines, or low supply pressure | Diagnose the fuel rail pressure sensor or pump lines |
| CA122 | Intake air pressure sensor feedback voltage too high | Sensor failure or wiring short to power | Verify the intake pressure sensor and wiring |
| CA123 | Intake air pressure sensor feedback voltage too low | Sensor short to ground or airflow restriction | Check for a sensor short or an airflow restriction |
| CA153 | Intake air temperature sensor feedback voltage too high | Sensor failure or wiring issue | Replace or test the IAT sensor |
| CA154 | Intake air temperature sensor feedback voltage too low | Sensor failure or wiring issue | Replace or test the IAT sensor |
| CA428 | Fuel moisture sensor feedback voltage too high | Sensor failure or wiring short | Ensure a clean fuel supply and check the moisture sensor harness |
| CA429 | Fuel moisture sensor feedback voltage too low | Sensor failure or wiring short to ground | Ensure a clean fuel supply and check the moisture sensor harness |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
4D84E-3B(S/N 00000-UP) attachments & work tools
Excavator Attachments
The Komatsu 4D84E-3B engine is specified for the PC50UU-2 mini excavator (serial range 12772-14992). Standard work tools for this class include digging buckets, grading buckets, and trenching buckets. Coupler systems are typically hydraulic quick couplers or fixed pin configurations compatible with the PC50UU-2 boom geometry. Hydraulic kit requirements vary by configuration/series depending on the specific tool's flow and pressure ratings.
Loader Attachments
The 4D84E-3B engine powers the SK815-5, SK815-5E0, SK815-5N, SK816-6, SK820-5, SK820-5N, and SK820-6 skid steer loaders. Typical work tools include general purpose buckets, grading buckets, and pallet forks. Mounting systems utilize standard skid steer quick-attach interfaces. Hydraulic arrangements require verification with the dealer as flow requirements vary by configuration/series for high-flow tool options.
All 4D84E-3B(S/N 00000-UP) assemblies by section
Every catalogued assembly group for the Komatsu 4D84E-3B(S/N 00000-UP). Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Accessory
Komatsu : 4d84e-3b(S/N 00000-Up) : Accessory : P.P.C. Pump And Mounting(#00141-)
| YM***20 | Pump Ass'Y,Hydraulic | 1 |
| YM***64 | Bearing,Ball | 2 |
| YM***81 | Gasket (Kit) | 1 |
Cooling System
Komatsu : 4d84e-3b(S/N 00000-Up) : Cooling System : Water Pump And Cooling Fan(#00142-)
| YM***20 | Gasket,Water Pump | 1 |
| YM***02 | Screw | 4 |
| YM***02 | Screw | 1 |
Cylinder Block
Komatsu : 4d84e-3b(S/N 00000-Up) : Cylinder Block : Camshaft And Tappet(#00141-)
| YM***80 | Camshaft Ass'Y | 1 |
| YM***01 | Gear Ass'Y,Camshaft | 1 |
| YM***50 | Bearing, Thrust | 1 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Cylinder Block : Crankshaft(#00141-)
| YM***00 | Gear,Crank | 1 |
| YM***80 | Parallel Pin | 1 |
| YM***50 | Pulley,Crank | 1 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Cylinder Block : Cylinder Block(#00141-)
| YM***60 | Cylinder Block, Assembly | 1 |
| YM***20 | Plug,Drain(Without Oil Cooler Type) | 1 |
| YM***00 | Plug | 1 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Cylinder Block : Flywheel And Flywheel Housing(#00141-)
| YM***02 | Screw | 6 |
| YM***90 | Flywheel Ass'Y | 1 |
| YM***80 | Parallel Pin | 4 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Cylinder Block : Front Cover And Gear(#00141-)
| YM***90 | Front Cover Ass'Y | 1 |
| YM***51 | Cap, Lub. Oil Supply | 1 |
| YM***52 | Bolt | 4 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Cylinder Block : Oil Pan(#00141-)
| YM***30 | Spacer | 1 |
| YM***52 | Screw | 2 |
| YM***52 | Screw | 24 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Cylinder Block : Piston And Connecting Rod(#00141-)
| YM***00 | Screw | 2 |
| YM***00 | Crank Pin Metal A. (Std) | 1 |
| YM***10 | Assembly, Piston (+0.25 mm) | 4 |
Cylinder Head
Komatsu : 4d84e-3b(S/N 00000-Up) : Cylinder Head : Air Cleaner And Mounting (Single Element Type)(#00141-)
| YM***41 | Buffle | 1 |
| YM***10 | Cap | 1 |
| YM***30 | Pan,Dust | 1 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Cylinder Head : Air Intake Manifold And Connection(#00141-)
Komatsu : 4d84e-3b(S/N 00000-Up) : Cylinder Head : Cylinder Head Cover(#00141-)
| YM***20 | Cover, Breather | 1 |
| YM***51 | Cap, Lub. Oil Supply | 1 |
| YM***00 | Clip,Breather Hose | 1 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Cylinder Head : Cylinder Head(#00141-)
| YM***80 | Retainer, Spring | 8 |
| YM***40 | Seal,Valve? Exhaust (Kit) | 4 |
| YM***10 | Valve,Exhaust | 4 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Cylinder Head : Exhaust Manifold And Muffler(#00141-)
| YM***02 | Screw | 6 |
| YM***00 | Manifold, Exhaust | 1 |
| YM***10 | Gasket (Kit) | 1 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Cylinder Head : Rocker Arm(#00141-)
| YM***02 | Nut,Rock | 3 |
| YM***02 | Screw | 7 |
| YM***80 | Spring | 4 |
Electrical System
Komatsu : 4d84e-3b(S/N 00000-Up) : Electrical System : Alternator (40a)(#00141-)
| YM***50 | Brush Ass'Y | 1 |
| YM***00 | Retainer,Bearing | 1 |
| YM***70 | Diode Ass'Y | 1 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Electrical System : Alternator And Mounting (40a)(#00141-)
| YM***30 | Plate,Adjust | 1 |
| YM***02 | Nut | 1 |
| YM***02 | Nut | 1 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Electrical System : Starting Motor (2kw)(#00141-)
| YM***50 | Pinion Ass'Y,Pinion | 1 |
| YM***20 | Housing,Center | 1 |
| YM***40 | Field Coil Ass'Y | 1 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Electrical System : Starting Motor And Mounting (2kw)(#00141-)
| YM***52 | Bolt Plated | 2 |
| YM***02 | Nut,Rock | 1 |
| YM***00 | Washer,Spring | 1 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Electrical System : Timer? Safety Relay And Grow Relay(#00141-)
| YM***20 | Timer,Solenoid | 1 |
| YM***10 | Relay,Stop Solenoid | 1 |
| YM***00 | Relay, Safety | 1 |
Fuel System
Komatsu : 4d84e-3b(S/N 00000-Up) : Fuel System : Fuel Filter And Piping(#00141-)
| YM***70 | Union | 1 |
| YM***00 | O-Ring (Kit) | 1 |
| YM***51 | Check Valve Ass'Y,Joint | 1 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Fuel System : Fuel Injection Pump (Governor) (1/2)(#00142-)
| YM***40 | Lever,Control | 1 |
| YM***30 | Spacer,Lever Shaft | 1 |
| YM***02 | Nut | 1 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Fuel System : Fuel Injection Pump (Governor) (2/2)(#00142-)
| YM***01 | Weight Assembly., Governor | 1 |
| YM***50 | Angleich Ass'Y | 1 |
| YM***00 | Washer,Spring | 1 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Fuel System : Fuel Injection Pump (Pump) (1/2)(#00142-)
| YM***50 | Kit, Shim | 1 |
| YM***10 | Plate? Caution | 1 |
| YM***90 | Key,Woodruff | 1 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Fuel System : Fuel Injection Pump (Pump) (2/2)(#00142-)
| YM***70 | Retainer, Spring | 4 |
| YM***00 | Rack,Control | 1 |
| YM***02 | Screw | 2 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Fuel System : Fuel Injection Pump And Piping(#00142-)
| YM***20 | Retainer, Pipe | 2 |
| YM***60 | O-Ring,Fuel Injection Pump | 1 |
| YM***02 | Nut | 1 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Fuel System : Fuel Nozzle And Spill Pipe(#00141-)
| YM***00 | Nozzle, Assembly | 1 |
| YM***20 | Spring | 1 |
| YM***00 | Fuel Injection Nozzle, Assembly | 1 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Fuel System : Water Separator And Piping(#00141-)
| YM***10 | Hose,(See Fig.0415-17?0416-17) | 1 |
| YM***00 | Gasket | 2 |
| YM***00 | O-Ring (Kit) | 1 |
Lubricating Oil System
Komatsu : 4d84e-3b(S/N 00000-Up) : Lubricating Oil System : Lubricating Oil Filter And Mounting(#00141-)
| YM***50 | Nut | 1 |
| YM***02 | Bolt Plated | 3 |
| YM***00 | Valve,Relief | 1 |
Komatsu : 4d84e-3b(S/N 00000-Up) : Lubricating Oil System : Lubricating Oil Pump And Piping(#00141-)
| YM***50 | Oil Pressure Transmitter | 1 |
| YM***50 | Pipe,Oil | 1 |
| YM***02 | Seal,Ring (Kit) | 2 |
Tool And Kit
Komatsu : 4d84e-3b(S/N 00000-Up) : Tool And Kit : Gasket Kit(#00141-)
| YM***60 | O-Ring,Fuel Injection Pump | 1 |
| YM***40 | Seal,Valve? Exhaust (Kit) | 4 |
| YM***20 | Gasket,Water Pump | 1 |
4D84E-3B(S/N 00000-UP) serial number reference
The PIN plate is typically riveted to the right-hand side of the cab on the lower frame (behind the front idler or beneath the operator's window) or stamped into the chassis frame casting on the right side. The prefix is the first three characters of the 17-character ISO PIN found on the emissions/export plate, or the engine model code stamped on the engine block/data plate.
| Prefix | Identifies | Notes |
|---|---|---|
| 4D84E-3B | Engine Model | Komatsu 4D84E-3B diesel engine. Sourced from the Komatsu 68E-88E Series Official Service Manual listing which explicitly ties this engine code to the PC50UU-2 model with serial number range 12772-14992. The manual lists subsequent variants (4D84E-3C, 4D84E-3D) for different serial ranges, confirming 4D84E-3B is a distinct generation/variant within this family. |
Frequently asked questions
What engine does the Komatsu PC50UU-2 use?
The PC50UU-2 uses the Komatsu 4D84E-3B engine for serial numbers 12772 through 14992, and the 4D84E-3C for serial numbers 14993 and up.
What is the operating weight of the Komatsu PC50UU-2?
The operating weight of the Komatsu PC50UU-2 varies by configuration, typically ranging from 11,000 to 12,000 lb (5,000 to 5,400 kg).
What replaced the Komatsu PC50UU-2?
The PC50UU-2 was succeeded by later generations of compact excavators in the PC50 series, which adopted updated emissions-compliant engines and revised chassis designs.
What 4D84E-3B(S/N 00000-UP) owners discuss
What is the specific application and serial range for the Komatsu 4D84E-3B engine?
What are the known hydraulic behaviors and common failure patterns for this machine type?
What undercarriage and wear patterns are typical for this class of excavator?
What are the common electrical and sensor issues for this engine series?
What engine quirks and maintenance points are specific to the 4D84E-3B?
What fluids and specifications should be used for this engine?
What should be checked when buying a used PC50UU-2 with the 4D84E-3B engine?
Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.
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