Komatsu 3D68E-3G(S/N 03402-UP)
Maintenance schedule, common problems & OEM parts breakdown
The Komatsu 3D68E-3G engine is a compact diesel powerplant designed for the PC12R-8 mini excavator class. This engine series supports machines in the sub-10-ton weight range, typically operating between 9,000 and 11,000 lbs depending on the configuration. Production for the PC12R-8 series with the 3D68E-3G engine began around 2003, succeeding earlier 3D68E variants in Komatsu's mini-excavator lineup. The 3G generation introduced specific emissions and performance updates compared to its predecessors. Configurations offered include standard and low-ground-pressure (LGP) undercarriage options, various stick lengths, and regional emissions packages that may alter the exact operating weight and hydraulic flow characteristics.
Across the 3D68E series generations, changes focused on meeting evolving emissions standards and improving fuel efficiency while maintaining the compact footprint required for urban construction. The 3G variant specifically addresses the transition period for Tier 2/interim emissions compliance in its market. In the used and parts market today, the 3D68E-3G remains significant because the PC12R-8 is a high-volume machine in the mini-excavator segment. Its widespread use in utility and landscaping work ensures steady demand for reliable replacement engines and components. The engine's compact design and proven durability make it a critical reference point for fleet managers managing older, cost-effective mini-excavator fleets.
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 3D68E-3G(S/N 03402-UP) specifications
Engine
| Model | 3D68E-3G |
| Application | Komatsu PC12R-8 (S/N 10001 and up) |
| Displacement | 0.78 l (47.8 cu. inch) |
| Cylinders | 3 |
| Net Power | 10.3 kW (13.8 HP) at 2450 rev / min |
| Gross Power | Not documented for this exact serial range — verify with your dealer |
| Emissions Tier | EPA Certified (referenced in shop manual SEBM011501) |
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 |
| Digging 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 3D68E-3G(S/N 03402-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 3D68E-3G(S/N 03402-UP) beyond the schedule
Predictive Maintenance & Fluid Analysis
Utilize KOWA fluid analysis at every 500-hour interval to monitor engine wear metals (iron, copper, lead, aluminum) and contaminants. Check coolant pH, SCA concentration, and glycol content to prevent corrosion in the 3D68E-3G cooling system. Monitor hydraulic oil particle count and viscosity to protect the PC12R-8's high-pressure pumps. Track fuel dilution and soot levels in the engine oil to assess combustion efficiency. Use KOMTRAX telematics to correlate load frequency with fluid degradation rates for precise service timing.
Corrective & Common Repairs
Address fuel system issues by regularly draining the water separator and replacing the fuel filter at 500 hours to protect the 3D68E-3G injection pump. Inspect the turbocharger for shaft play and seal leaks during the 1,000-hour service. Check the air filter restriction indicator daily; replace the outer element at 1,000 hours or when clogged. Inspect hydraulic hoses for abrasion against the boom and stick, replacing worn lines before failure. Verify battery terminal tightness and alternator output to prevent electrical faults in the compact PC12R-8 chassis.
Overhaul & Rebuild Points
Plan major engine overhaul based on KOWA analysis trends and compression test results for the 3D68E-3G. Inspect the turbocharger bearings and replace if shaft play exceeds limits during the 1,000-hour check. Evaluate the hydraulic pump and swing motor wear during the 2,000-hour comprehensive evaluation. Check final drive oil for metal particles indicating gear wear. Inspect structural welds on the boom and stick for fatigue cracks during the 1,000-hour structural inspection. Monitor undercarriage wear measurements to determine track chain and sprocket replacement needs.
Seasonal & Environment Servicing
In cold climates, check coolant freeze protection before winter to prevent block damage in the 3D68E-3G. Use appropriate viscosity engine oil (e.g., SAE 5W-30 or 10W-30 depending on ambient temperature) to ensure proper lubrication during startup. In dusty environments, inspect the air filter more frequently and clean the radiator fins daily to prevent overheating. In high-humidity areas, check for water contamination in the fuel separator more often. Ensure the DEF system is protected from freezing if equipped, and verify battery health in extreme temperatures.
3D68E-3G(S/N 03402-UP) common service parts
| Part number | Part | Notes | |
|---|---|---|---|
| YM129053-55620 | Fuel Filter Ass'Y | Fuel system service | Check fitment → |
| YM102103-55520 | O-Ring,(For Fuel Filter) | Fuel system service | Check fitment → |
| (YM129053-55620) | Fuel Filter Ass'Y,(See Fig.A4110-B0a3) | Fuel system service | Check fitment → |
| YM171051-92760 | Wrench,Fuel Filter? Water Separator | Fuel system service | Check fitment → |
| YM119332-92751 | Wrench,(For Engine Oil Filter) | Lubrication service | Check fitment → |
Always confirm against your machine's serial number — cross-check any part in Heavy Parts AI before ordering.
3D68E-3G(S/N 03402-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 the voltage at the pin connector |
| CA441 | Battery voltage too low | Alternator failure, battery degradation, or voltage regulator fault | Replace the alternator or battery; check the voltage regulator |
| CA442 | Battery voltage too high | Alternator overcharging or voltage regulator malfunction | Replace the alternator or battery; check the voltage regulator |
| CA122 | Intake air pressure sensor feedback voltage too high | Sensor malfunction or wiring short | Verify the intake pressure sensor and wiring |
| CA123 | Intake air pressure sensor feedback voltage too low | Sensor short or airflow restriction | Check for a sensor short or an airflow restriction |
| CA153 | Intake air temperature sensor feedback voltage too high | Sensor malfunction | Replace or test the IAT sensor |
| CA154 | Intake air temperature sensor feedback voltage too low | Sensor malfunction | Replace or test the IAT sensor |
| CA451 | Common rail pressure sensor feedback value too high | Fuel rail sensor malfunction or actual overpressure condition | Diagnose the fuel rail pressure sensor or pump lines |
| CA452 | Common rail pressure sensor feedback value too low | Fuel rail sensor malfunction or low pressure condition | Diagnose the fuel rail pressure sensor or pump lines |
| CA234 | Engine overspeed | Throttle calibration error, engine load cycle issue, or operator misuse | Verify throttle calibration, engine load cycle, or operator misuse |
Codes and remedies are general guidance for this model family — always confirm with diagnostic tooling and your dealer before major repairs.
3D68E-3G(S/N 03402-UP) attachments & work tools
Excavator Attachments
The Komatsu 3D68E-3G engine is installed in the PC12R-8 mini excavator. Factory documentation lists compatible work tools for this model class, including standard digging buckets, trenching buckets, and grading buckets. Coupler systems for these tools are model-specific to the PC12R-8 boom and arm configuration.
Hydraulic Breakers
Hydraulic breakers are offered as an option for the PC12R-8 series. These attachments require a dedicated hydraulic kit and piping arrangement to connect to the machine's auxiliary hydraulic circuit. Factory guarding options and mounting brackets are specified for this size class to ensure structural integrity during operation.
Engine Specifications
The 3D68E-3G is a diesel engine used in the PC12R-8 excavator with serial numbers starting from 10001. It is part of the 68E-88E series of Komatsu diesel engines. The engine is EPA certified and includes specific service information for CARB and ULG regulations in the official shop manual.
All 3D68E-3G(S/N 03402-UP) assemblies by section
Every catalogued assembly group for the Komatsu 3D68E-3G(S/N 03402-UP). Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.
Engine
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Air Cleaner And Mounting
| YM***80 | Air Cleaner Support, Assembly | 1 |
| YM***00 | Stay | 1 |
| YM***40 | Valve,Unloader | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Air Intake Manifold And Connection
| YM***10 | Gasket, Suction Manifold | 1 |
| YM***82 | Bolt | 1 |
| YM***01 | Manifold,Air Intake | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Alternator (Inner Parts)
| YM***00 | Stator Ass'Y | 1 |
| YM***02 | Alternator A. (20a) | 1 |
| YM***00 | Nut,Ball | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Alternator And Mounting
| YM***02 | Bolt Plated | 1 |
| YM***02 | Nut | 1 |
| YM***50 | Bolt | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Camshaft And Tappet
| YM***00 | Tappet | 6 |
| YM***50 | Retainer, Bearing | 1 |
| YM***22 | Screw | 2 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Crankshaft
| YM***00 | Gear,Crank | 1 |
| YM***80 | Bolt | 1 |
| YM***41 | Washer | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Cylinder Block
| YM***00 | Plug | 2 |
| YM***00 | Main Metal Ass'Y (Std) | 4 |
| YM***00 | Plug | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Cylinder Block Accsessory
| YM***50 | Oil Pressure Transmitter | 1 |
| YM***00 | Gauge,Oil Level | 1 |
| YM***20 | Plug,Drain(Without Oil Cooler Type) | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Cylinder Head
| YM***00 | Screw | 14 |
| YM***10 | Valve, Exhaust | 3 |
| YM***40 | Seat,Intake And Exhaust (Kit) | 6 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Cylinder Head Cover
| YM***51 | Cap, Lub. Oil Supply | 1 |
| YM***10 | Gasket,Head Cover (Kit) | 1 |
| YM***50 | Pipe,Breather | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Drive Gear
| YM***22 | Retainer, Idle Gear | 1 |
| YM***00 | Ring, Snap | 1 |
| YM***52 | Shaft,Idler Gear | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Electrical Parts (Forwerded Individually Parts)
| YM***21 | Indicator, Charging | 1 |
| YM***20 | Timer,Solenoid | 1 |
| YM***10 | Relay,Stop Solenoid | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Exhaust Manifold And Muffler
| YM***00 | Manifold, Exhaust | 1 |
| YM***22 | Stud | 2 |
| YM***02 | Stud | 2 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Flywheel And Flywheel Housing
| YM***20 | Bolt Plated | 3 |
| YM***20 | Parallel Pin | 2 |
| YM***80 | Parallel Pin | 2 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Front Cover
| YM***51 | Cap, Lub. Oil Supply | 1 |
| YM***40 | O-Ring,Drain Plug | 1 |
| YM***62 | Bolt Plated | 7 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Fuel Filter
| YM***40 | Lever | 1 |
| YM***00 | O-Ring (Kit) | 1 |
| YM***50 | Cartridge | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Fuel Filter And Piping
| YM***80 | Pipe | 1 |
| YM***20 | Pipe, Fuel, Assembly | 1 |
| YM***50 | Bolt, Pipe Joint | 2 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Fuel Injection Pump (Pump) (Inner Parts)
| YM***00 | Washer,Spring | 2 |
| YM***00 | Washer | 2 |
| YM***50 | Shim Ass'Y | 3 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Fuel Injection Pump And Piping
| YM***20 | Retainer, Pipe | 1 |
| YM***30 | Pipe,Injection? No.3 | 1 |
| YM***10 | Pipe,Injection? No.1 | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Fuel Nozzle And Spill Hose
| YM***40 | Spacer, Valve Stop | 1 |
| YM***00 | Fuel Injection Valve, Assembly | 3 |
| YM***80 | Nut | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Gasket Kit
| YM***10 | Gasket, Suction Manifold | 1 |
| YM***10 | Gasket Kit | 1 |
| YM***10 | Gasket,Head Cover (Kit) | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Glow Plug
| YM***00 | Glow Plug | 3 |
| YM***20 | Connection Plugs | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Governor Control
| YM***00 | Pin, Cotter | 1 |
| YM***00 | Retainer, Shaft | 1 |
| YM***30 | Screw,Adjust | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Lubricating Oil Pump
| YM***22 | Screw | 2 |
| YM***81 | Pipe,Inlet | 1 |
| YM***20 | O-Ring,Cylinder Head Cover Bolt | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Oil Filter
| YM***50 | Nut | 1 |
| YM***00 | Valve Ass'Y | 1 |
| YM***50 | Cartridge,Engine Oil | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Oil Pan
| YM***40 | Plug,Drain | 1 |
| YM***52 | Bolt Plated | 20 |
| YM***70 | Oil Pan Ass'Y | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Piston And Connecting Rod
| YM***00 | Piston Ring Ass'Y | 1 |
| YM***10 | Bearing (--0.25 mm) | 1 |
| YM***80 | Piston Ass'Y | 3 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Rocker Arm
| YM***30 | Screw,Adjusting | 2 |
| YM***50 | Rocker Arm Ass'Y,Intake | 3 |
| YM***02 | Nut | 2 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Starting Motor (0.8kw) (Inner Parts)
| YM***00 | Stopper Set | 1 |
| YM***10 | Holder Brush, Assembly | 1 |
| YM***70 | Magnetic Switch A | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Starting Motor And Mounting (0.8kw)
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Tool
| YM***60 | Wrench,Fuel Filter? Water Separator | 1 |
| YM***50 | Screw Driver | 1 |
| YM***51 | Wrench,(For Engine Oil Filter) | 1 |
Komatsu : 3d68e-3g(S/N 03402-Up) : Engine : Water Pump And Cooling Fan
| YM***02 | Screw | 4 |
| YM***20 | Gasket (Kit) | 1 |
| YM***60 | Spacer | 1 |
3D68E-3G(S/N 03402-UP) serial number reference
The engine serial number plate is typically located on the left side of the engine block near the injection pump or on a metal plate affixed to the engine. The prefix is the engine model code (e.g., 3D68E-3G) stamped on this plate, distinct from the machine's chassis PIN. Verify the engine model against the machine's data plate to ensure correct parts fitment.
| Prefix | Identifies | Notes |
|---|---|---|
| 3D68E-3G | Engine Model | The engine model code 3D68E-3G is stamped on the engine data plate, typically located on the left side of the engine block near the injection pump. This prefix identifies the specific engine configuration for the 3D68E-3G family. Serial range 03402-UP is explicitly tied to this engine model in parts catalogs and service manuals. No 3-character PIN prefixes are documented for this specific engine serial range in the provided sources; the designation is the engine model code itself. |
Frequently asked questions
What engine does the Komatsu PC12R-8 use?
The Komatsu PC12R-8 mini excavator uses the 3D68E-3G diesel engine for serial numbers 10001 and up.
What is the operating weight of the Komatsu PC12R-8?
The operating weight of the Komatsu PC12R-8 varies by configuration, typically ranging from 9,182 to 11,000 lbs (4,165 to 4,990 kg) depending on the undercarriage type and attachment package.
What replaced the Komatsu PC12R-8?
The PC12R-8 was succeeded by later generations in Komatsu's mini-excavator lineup, such as the PC12R-10 and subsequent models in the PC12 series, which feature updated emissions-compliant engines and improved hydraulic systems.
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