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Hitachi’s Heavy Excavator Line and the ZX670LCH-3
The Hitachi ZX670LCH-3 is part of Hitachi Construction Machinery’s large excavator lineup, designed for high-production mining, quarrying, and heavy earthmoving. Introduced in the mid-2000s, the ZX-3 series featured advanced electronic control systems, fuel-efficient engines, and robust hydraulic architecture. The 670LCH-3, weighing over 67 metric tons and powered by a 345 kW (460 HP) Isuzu engine, was engineered to deliver high breakout force and long-term durability in demanding environments.
Hitachi, founded in 1970 as a construction division of the larger Hitachi Ltd., has sold tens of thousands of large excavators globally. The ZX670LCH-3 was especially popular in Africa, Southeast Asia, and Australia, where its mechanical reliability and electronic diagnostics were appreciated by fleet managers and technicians alike.
Symptoms and Initial Failures
One unit operating in West Africa began exhibiting intermittent shutdowns over several weeks. Eventually, the machine failed entirely during transport and would not restart. Diagnostic software revealed multiple fault codes, including:
Terminology Notes
The presence of a ROM fault raised concerns about a corrupted or damaged ECM. However, further investigation revealed that the G sensor shares wiring with the rail pressure sensor and EGR position sensor. A fault in one could cascade across the system.
Technicians attempted to clear fault codes using MPDr software (version M Pro 2.12.0.1), but the system was stubborn. Even after replacing sensors and swapping components from a working ZX870, the 670LCH-3 refused to start. The software failed to provide detailed fault descriptions, and retrying the fault-clearing process multiple times yielded no success.
Eventually, the team unplugged the EGR motor and rail pressure sensor, isolating the G sensor. This allowed the engine to begin energizing injectors—confirming that the G sensor fault was the primary blocker. Resistance tests between the ECM and sensor terminals revealed degraded shielding and multiple spliced joints in the engine harness, likely contributing to signal interference.
Sensor Fault Code Breakdown
In several cases, operators reported that spilled drinks or cleaning fluids had leaked into the cab and onto control modules behind the seat. This led to corrosion and erratic behavior. One machine was down for two weeks during the holidays due to a flipped fuel shutoff switch—hidden beneath the operator’s seat.
In Burkina Faso, a technician noted that the shielding around the engine harness had been stripped back during previous repairs. While continuity tests showed good results, the lack of shielding allowed electromagnetic interference to disrupt sensor signals.
Recommendations for Repair and Prevention
To restore functionality and prevent future failures:
Hitachi’s diagnostic tools, while powerful, can be opaque without proper training. The MPDr platform requires familiarity with fault code logic and controller architecture. On Dash-3 machines, engine codes are particularly resistant to clearing, and wiring faults often masquerade as sensor failures.
Hitachi’s service manuals and dealer support remain essential for resolving complex electrical issues. In regions without dealer access, technicians rely on shared knowledge, trial-and-error, and component swaps from similar models.
Conclusion
The Hitachi ZX670LCH-3 is a powerhouse excavator, but its reliance on integrated electronics means that small faults—especially in shared wiring circuits—can cripple the entire machine. By understanding the relationships between sensors, shielding, and fault logic, technicians can navigate even the most stubborn failures. In the world of heavy iron, sometimes the fix isn’t in the sensor—it’s in the wire that connects them all.
The Hitachi ZX670LCH-3 is part of Hitachi Construction Machinery’s large excavator lineup, designed for high-production mining, quarrying, and heavy earthmoving. Introduced in the mid-2000s, the ZX-3 series featured advanced electronic control systems, fuel-efficient engines, and robust hydraulic architecture. The 670LCH-3, weighing over 67 metric tons and powered by a 345 kW (460 HP) Isuzu engine, was engineered to deliver high breakout force and long-term durability in demanding environments.
Hitachi, founded in 1970 as a construction division of the larger Hitachi Ltd., has sold tens of thousands of large excavators globally. The ZX670LCH-3 was especially popular in Africa, Southeast Asia, and Australia, where its mechanical reliability and electronic diagnostics were appreciated by fleet managers and technicians alike.
Symptoms and Initial Failures
One unit operating in West Africa began exhibiting intermittent shutdowns over several weeks. Eventually, the machine failed entirely during transport and would not restart. Diagnostic software revealed multiple fault codes, including:
- G sensor failure
- Crankshaft position sensor fault
- Boost pressure sensor low voltage
- Fuel pump malfunction
- ROM error on the engine controller
Terminology Notes
- G Sensor: A gravity or acceleration sensor used to detect machine orientation or motion; critical for safety and engine logic.
- ROM Error: A fault in the read-only memory of the ECM, often indicating corruption or hardware failure.
- ECM (Engine Control Module): The computer that manages engine functions, including fuel injection, timing, and sensor inputs.
The presence of a ROM fault raised concerns about a corrupted or damaged ECM. However, further investigation revealed that the G sensor shares wiring with the rail pressure sensor and EGR position sensor. A fault in one could cascade across the system.
Technicians attempted to clear fault codes using MPDr software (version M Pro 2.12.0.1), but the system was stubborn. Even after replacing sensors and swapping components from a working ZX870, the 670LCH-3 refused to start. The software failed to provide detailed fault descriptions, and retrying the fault-clearing process multiple times yielded no success.
Eventually, the team unplugged the EGR motor and rail pressure sensor, isolating the G sensor. This allowed the engine to begin energizing injectors—confirming that the G sensor fault was the primary blocker. Resistance tests between the ECM and sensor terminals revealed degraded shielding and multiple spliced joints in the engine harness, likely contributing to signal interference.
Sensor Fault Code Breakdown
- 102-3: Boost pressure sensor low voltage
- 636-2: G sensor fault (critical for startup)
- 10001-3: EGR position sensor fault
- 157-3: Common rail pressure sensor high voltage
- 13311-4: Fuel level sensor fault
- 1381-3: Unrecognized code, possibly proprietary or regional
In several cases, operators reported that spilled drinks or cleaning fluids had leaked into the cab and onto control modules behind the seat. This led to corrosion and erratic behavior. One machine was down for two weeks during the holidays due to a flipped fuel shutoff switch—hidden beneath the operator’s seat.
In Burkina Faso, a technician noted that the shielding around the engine harness had been stripped back during previous repairs. While continuity tests showed good results, the lack of shielding allowed electromagnetic interference to disrupt sensor signals.
Recommendations for Repair and Prevention
To restore functionality and prevent future failures:
- Replace the G sensor with OEM parts and verify resistance across terminals
- Rebuild or replace the engine harness with proper shielding and sealed connectors
- Use dielectric grease on all sensor plugs to prevent moisture ingress
- Install drip guards or enclosures over cab-mounted controllers
- Train operators to avoid placing bottles or cleaning agents near sensitive electronics
- Use MPDr software and hit “Retry” repeatedly—up to 20 times if needed
- Clear faults via the monitor by holding the top-right button during ignition, then navigating to “Service” → “Troubleshoot”
- Prioritize active faults; codes visible on the monitor are current and must be addressed before startup
Hitachi’s diagnostic tools, while powerful, can be opaque without proper training. The MPDr platform requires familiarity with fault code logic and controller architecture. On Dash-3 machines, engine codes are particularly resistant to clearing, and wiring faults often masquerade as sensor failures.
Hitachi’s service manuals and dealer support remain essential for resolving complex electrical issues. In regions without dealer access, technicians rely on shared knowledge, trial-and-error, and component swaps from similar models.
Conclusion
The Hitachi ZX670LCH-3 is a powerhouse excavator, but its reliance on integrated electronics means that small faults—especially in shared wiring circuits—can cripple the entire machine. By understanding the relationships between sensors, shielding, and fault logic, technicians can navigate even the most stubborn failures. In the world of heavy iron, sometimes the fix isn’t in the sensor—it’s in the wire that connects them all.
