Part of the Doosan Repair Manuals.
This is the factory shop manual for the Doosan DX420LC-3 crawler excavator, publication 950106-00398E, July 2012 edition. It covers the whole 41,350 kg machine: the Isuzu 6UZ1 inline six rated 270 kW (367 hp), the A8VO200 main pump, main control valve, swing and travel devices, cylinders, the full electrical system, and boom/arm removal. The engine section alone runs from basic specs through compression testing, fuel system checks, DPD control, and a dedicated DTC Information sub-chapter spanning pages 378 to 455. You also get a complete hydraulic schematic (page 1705) and electrical schematic (page 1869). If you are rebuilding a pump, chasing a fault code, or pulling the counterweight, this is the book Doosan techs used.
What's Inside This Doosan DX420LC-3 Manual
| System | Pages | Key Topics |
|---|---|---|
| Safety | 5-72 | Track Excavator Maintenance Safety, Safety Messages, Signal Words, Other Signal Words, Safety Decals, Safe Operation Is Operator's Responsibility |
| Specifications and General Maintenance | 73-138 | Specification for DX420LC-3, General Description, Component Locations, Overall Dimensions, Working Range, General Specifications |
| Upper Structure and Lower Structure and Chassis | 139-234 | Cabin, Cabin Identification, Rollover Protective Structure (ROPS), Removal, Installation, Counterweight |
| Engine and Drivetrain - Service Information Guide | 235-259 | Engine, Safety Information, Service Information Guide, Contents Included in Service Information, Plastic Gauge, Recommended Liquid Gasket |
| Engine and Drivetrain - Maintenance Information | 260-338 | Maintenance Information, Maintenance Precautions, Primary Specifications, Function, Structure, Operation, Introduction to the Trouble Diagnosis |
| Engine and Drivetrain - Functional Inspection and Symptom | 339-377 | Functional Inspection, Engine Compression Pressure Inspection, Fuel System Check, Air Intake System Check, Exhaust System Check, DPD Control System Check |
| Engine and Drivetrain - DTC Information | 378-455 | DTC Information, DTC P0016 (Flash Code 16) Crankshaft Position - Camshaft Position Correlation, DTC P0045 (Flash Code 33) Turbocharger Boost Control Solenoid Circuit, DTC P0087 (Flash Code 225) Fuel Rail/ System Pressure - Too Low, DTC P0088 (Flash Code 118) Fuel Rail/ System Pressure - Too High, DTC P0089 (Flash Code 151) Fuel Pressure Regulator Performance |
| Engine and Drivetrain - Engine Control | 456-601 | Engine Control, DTC P0016 (Flash Code 16) Crankshaft Position - Camshaft Position Correlation, DTC P0045 (Flash Code 33) Turbocharger Boost Control Solenoid Circuit, DTC P0087 (Flash Code 225) Fuel Rail/ System Pressure - Too Low, DTC P0088 (Flash Code 118) Fuel Rail/ System Pressure - Too High, DTC P0089 (Flash Code 151) Fuel Pressure Regulator Performance |
| Engine and Drivetrain - Mechanical | 602-962 | Mechanical, Cylinder Head Cover, Cylinder Head Assembly, Idle Gear, Cylinder Block, Crankshaft |
| Engine and Drivetrain - Fuel System | 963-1023 | Fuel System, Fuel Supply Pump, Injector, Common Rail Assembly, Fuel Filter, Pressure Limiter |
| Engine and Drivetrain - Cooling and Lubrication | 1024-1090 | Cooling, Water Pump Assembly, Thermostat, Radiator, Overheat Switch, Engine Coolant Temperature Sensor |
| Engine and Drivetrain - Induction to Electrical | 1091-1164 | Induction, Boost Temperature Sensor, Turbocharger Assembly, Intercooler, Air Cleaner Filter, IMT Sensor |
| Engine and Drivetrain - Wiring Diagram to Drive Coupling (Main Pump) | 1165-1218 | Wiring Diagram, Using the Wiring Diagram, Location Diagram, Engine, Connector List, Engine Coolant Heater (Option) |
| Hydraulics - Hydraulic System Troubleshooting, Testing and Adjustment to Center Joint (Swivel) | 1219-1276 | Hydraulic System Troubleshooting, Testing and Adjustment, Hydraulic System - General Notes, Hydraulic Schematic, General Notes, Operation of Working Components, Boom Operating Circuit |
| Hydraulics - Cylinders and Swing Device | 1277-1370 | Cylinders, General Description, Theory of Operation, Parts List, Special Tools and Materials, Piston Nut |
| Hydraulics - Travel Device | 1371-1430 | Travel Device, Basic Structure and Drawings, Operation Principle, Operation Instructions, Troubleshooting, Maintenance Instructions |
| Hydraulics - Main Pump | 1431-1486 | Main Pump, Sectional View, A8VO200LA1KH1/63, General Repair Guidelines, Seal Kits and Subassemblies, Sealing the Driveshaft |
| Hydraulics - Gear Pump to Fan Pump | 1487-1566 | Gear Pump, Disassembling Single Gear Pump (Opt), Reassembling Single Gear Pump (Opt), Fan Motor for Oil Cooler, Disassembly, Assembly |
| Hydraulics - Main Control Valve | 1567-1624 | Main Control Valve, General Description, When All Spools Are in Neutral, Single Operation, Combined Operation, Antidrift Valve |
| Hydraulics - Remote Control Valve (Work Lever / Joystick) to Hydraulic Schematic | 1625-1706 | Remote Control Valve (Work Lever / Joystick), General Description, Theory of Operation, Parts List, Specifications, Torques |
| Electrical System | 1707-1870 | Electrical Supply System, Engine Starting Circuit, Start Operation, After Start, Engine Preheating System |
| Attachments | 1871-1902 | Boom and Arm, Front Attachment Pin Specifications, DX420LC-3, Front Attachment - Removal and Installation, Arm Removal Procedure, Boom Removal Procedure |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Engine model | Isuzu 6UZ1, inline 6-cylinder | p. 265 |
| Rated power | 270 kW (367 hp) | p. 265 |
| Shipping weight, standard track | 41,350 kg (91,161 lb) | p. 88 |
| Counterweight | 8,200 kg (18,078 lb) | p. 88 |
| Standard boom weight | 3,098 kg (6,829 lb) | p. 88 |
| Fuel tank capacity | 640 liters (169 U.S. gal) | p. 88 |
| Optional shoe weight penalty | add 720 kg (1,590 lb) for 750 mm (30") shoes | p. 88 |
Doosan DX420LC-3 Common Problems This Manual Covers
Hydraulics run hot, the pump gets noisy, or digging and travel power fades
Start with oil level and condition, then inspect drained oil and filters for metal or moisture before condemning the pump. The Hydraulic System Troubleshooting, Testing and Adjustment chapter gives the test procedure and pressure values; the Main Pump chapter covers case drain checks and rebuild with seal kits for the A8VO200.
Manual Section: Hydraulics - Hydraulic System Troubleshooting, Testing and Adjustment p. 1443Engine overheats under load or coolant level keeps dropping
Check the expansion tank and hoses for leaks, belt tension, and water pump circulation before blaming the radiator. The Cooling and Lubrication chapter covers the water pump assembly, thermostat, radiator, overheat switch, and coolant temperature sensor with inspection specs, so you can test each piece instead of swapping parts blind.
Manual Section: Engine and Drivetrain - Cooling and Lubrication p. 1115Hard starting, weak cranking, or intermittent electrical faults on the dash
Chase battery condition, terminals, grounds, and the charging circuit first - most of these complaints are wiring, not the starter. The Electrical System chapter maps the engine starting circuit through start, after start, and preheating, and the connector list plus location diagram in the wiring section lets you find and test each plug on the machine.
Manual Section: Electrical System p. 378Weak or jerky travel, or grinding noise from the final drives
The Travel Device chapter lays out the basic structure, operation principle, a dedicated troubleshooting table, and maintenance instructions, so you can separate a worn travel motor from undercarriage wear or a pilot pressure problem before splitting the final drive. Pressure checks tie back to the hydraulic testing chapter.
Manual Section: Hydraulics - Travel Device p. 641Frequently Asked Questions
What does an error code mean on a Doosan DX420LC-3?
The manual has a dedicated DTC Information sub-chapter running from page 378 to page 455. Each trouble code gets its own entry with the flash code, the circuit involved, and a step-by-step diagnostic procedure - for example crank/cam correlation, turbo boost solenoid circuit, and rail pressure too low or too high. You look up the code the machine shows, then follow the checks in order instead of guessing at parts. p. 378
How do I clear a fault code or service indication on the DX420LC-3?
Codes on this machine clear once the underlying fault condition is actually fixed and verified, and the DTC chapter tells you how to confirm that per code. The Introduction to the Trouble Diagnosis section in the Maintenance Information chapter walks through the diagnostic flow so you fix the cause instead of just wanting the light off. There is no shortcut button worth chasing - a code that comes back means the circuit check was skipped. p. 265
Are the torque specs for the main pump in this manual?
Yes. The Main Pump chapter covers the A8VO200LA1KH1/63 with a sectional view, general repair guidelines, seal kits and subassemblies, and driveshaft sealing procedure. Fastener torques and assembly values are given in the service procedures, and the Remote Control Valve chapter carries its own torque tables too. Do not reuse generic Rexroth numbers off the internet - use the values printed for this pump build. p. 1705
Does it include full hydraulic and electrical schematics?
Both. The complete hydraulic schematic (drawing SP002671) is on page 1705 and the full electrical schematic (SP002572) is on page 1869. The wiring section also includes a location diagram and connector list, so you can find the actual plug on the machine, not just the symbol on paper. Note the electrical sheet is a Doosan family drawing, but this book is for the DX420LC-3 only. p. 88
Which engine does this manual cover, and how do I check hydraulic pressures?
The engine is the Isuzu 6UZ1 inline 6-cylinder, 270 kW (367 hp) - not the 6WG1 used in the bigger DX490LC-3, so make sure this matches your machine. Pressure testing and relief adjustment are covered in the Hydraulic System Troubleshooting, Testing and Adjustment chapter, which gives the test ports, procedures, and target values for setting main relief and pilot pressures correctly. p. 1869
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