What is Hitachi ZX690LCH-5A Fault Code 14107-2?

Fault Code 14107-2 indicates a hydraulic oil temperature sensor circuit malfunction, specifically detecting an abnormal voltage signal (typically low voltage or short to ground) in the temperature monitoring system. This code triggers when the Engine Control Module (ECM) receives sensor data outside the acceptable voltage range of 0.5-4.5V, preventing accurate monitoring of hydraulic oil temperature.

This fault is critical for the ZX690LCH-5A because hydraulic oil temperature directly affects system efficiency, component longevity, and operational safety. When the ECM cannot accurately read oil temperature, the machine may enter a protective derate mode or fail to warn operators of overheating conditions that could damage expensive hydraulic components like pumps, motors, and cylinders.

Common Symptoms

• Hydraulic temperature warning lamp illuminated on the instrument panel, even when oil feels cool to touch
• Reduced engine power or RPM limitation as the ECM enters protective mode
• Erratic temperature gauge readings that fluctuate wildly or show constant maximum/minimum values
• Stored diagnostic trouble codes visible through service mode or diagnostic software
• Intermittent code activation during machine warm-up or specific operating conditions, particularly in used excavators with weathered wiring

Potential Causes

The most common causes for Code 14107-2 on used ZX690LCH-5A excavators include:

• Damaged or corroded sensor connector at the hydraulic tank, especially where the harness routes near sharp metal edges
• Failed hydraulic oil temperature sensor due to age-related internal resistance changes or moisture infiltration
• Wiring harness chafing at known rub points between the tank and main harness bundle near the swing bearing area
• Poor ground connection at sensor mounting points caused by rust or loose hardware
• ECM internal fault (rare) affecting the sensor input circuit
• Contaminated hydraulic oil creating conductive paths or sensor fouling

How to Troubleshoot and Fix Code 14107-2

Step 1: Visual Inspection Locate the hydraulic oil temperature sensor on the hydraulic tank (passenger side, mid-tank level). Inspect the connector for corrosion, oil contamination, or pushed-back pins. On used excavators, check the wiring harness routing for wear marks where it contacts the tank or frame—this is a common failure point after 5,000+ hours.

Step 2: Electrical Testing Disconnect the sensor and measure resistance across sensor terminals using a digital multimeter. At 68°F (20°C), resistance should read approximately 2,200-2,800 ohms. If readings show open circuit (infinite resistance) or near-zero resistance, replace the sensor. Check harness continuity from sensor connector to ECM pins—reference should show less than 5 ohms resistance.

Step 3: Voltage Signal Verification With ignition ON and sensor connected, backprobe the signal wire (typically yellow/white) at the connector. Voltage should read 0.5-4.5V depending on temperature. Readings below 0.3V indicate a short to ground; above 4.8V suggests an open circuit or failed sensor.

Step 4: Advanced Diagnostics Use Hitachi Dr.EX diagnostic software to monitor live sensor data and compare actual oil temperature (use infrared thermometer on tank surface) with displayed values. A variance greater than 15°F confirms sensor replacement needed.

Important for Used Equipment: Before replacing components, thoroughly clean all ground connections at the sensor mounting bolt and spray electrical contact cleaner into connectors. Many "sensor failures" on older machines are actually corrosion-related connection issues.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Hitachi ZX690LCH-5A service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs may void warranties or create safety hazards.