What is Hitachi ZX360LC-5G Fault Code 14105-2?

Fault Code 14105-2 indicates a hydraulic oil temperature sensor circuit malfunction, specifically a high voltage condition in the sensor circuit. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects an abnormally high voltage signal from the hydraulic oil temperature sensor, typically exceeding 4.5 volts when normal operating range should be between 0.5-4.5 volts.

This code is critical for the ZX360LC-5G because the hydraulic oil temperature directly affects system efficiency, component longevity, and operator safety. When the ECM cannot accurately monitor hydraulic temperatures, the machine may enter derate mode to prevent potential damage to hydraulic pumps, motors, and seals. On used excavators, this sensor circuit is particularly vulnerable to degradation from years of exposure to heat, vibration, and contaminants.

Common Symptoms

• Hydraulic temperature warning light illuminated on the instrument cluster
• Reduced hydraulic performance or machine entering protective derate mode, limiting swing speed and boom/arm movements
• Erratic temperature gauge readings or gauge reading abnormally low (indicating open circuit)
• Intermittent fault activation, especially during cold starts or after extended operation
• ECM storing active or pending codes visible through diagnostic software

Potential Causes

The most common technical causes for Code 14105-2 on used ZX360LC-5G excavators include:

• Open circuit in sensor wiring harness caused by wire breakage, particularly at flex points near the hydraulic tank or along the chassis rail where harness routing creates friction points
• Failed hydraulic oil temperature sensor with internal open circuit (common failure mode after 8,000+ operating hours)
• Corroded or loose connector terminals at the sensor plug or ECM harness connection, especially on machines operated in coastal or high-humidity environments
• Damaged sensor connector pins from improper disconnection during previous maintenance
• Chafed wiring insulation exposing bare wire to ground contact, creating intermittent high-resistance conditions
• ECM internal fault (rare, but possible on high-hour machines with previous electrical issues)

How to Troubleshoot and Fix Code 14105-2

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor mounted on the hydraulic tank (typically on the return line filter housing). Inspect the sensor connector for corrosion, bent pins, oil contamination, or moisture intrusion. Check the wiring harness from sensor to ECM for visible damage, chafing, or burns, paying special attention to areas where the harness contacts frame members or passes through bulkheads.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to measure resistance across the sensor terminals. At 20°C (68°F), resistance should read approximately 2,000-3,000 ohms (consult service manual for exact specifications). If the reading shows infinite resistance (OL), the sensor has failed internally. Next, check for continuity in the harness by measuring resistance from the sensor connector pins to the corresponding ECM pins (typically less than 5 ohms). High resistance indicates damaged wiring.

Step 3: Voltage Signal Testing With the sensor connected and ignition ON (engine OFF), backprobe the sensor connector and measure voltage between the signal wire and ground. You should see approximately 5 volts (reference voltage from ECM). If voltage reads 5V constantly, disconnect the sensor; if voltage remains at 5V with sensor disconnected, the sensor is confirmed faulty. If voltage drops to 0V, suspect wiring short to ground.

Step 4: Advanced Diagnostics Connect Hitachi Dr.EX diagnostic software to verify real-time sensor data and freeze frame information. Compare actual hydraulic oil temperature (use infrared thermometer on tank) with ECM-displayed temperature. On used excavators, inspect the sensor mounting boss for cracks or thread damage that could cause poor sensor grounding, and clean all connector terminals with electrical contact cleaner before reassembly.

Step 5: Repair and Verification Replace faulty components (sensor approximately $85-150, harness repair typically $200-400 if professionally done). After repairs, clear codes, operate machine through full temperature range, and verify code does not return. For used machines, consider applying dielectric grease to connectors and securing harnesses with new zip ties away from heat sources.

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Disclaimer: This guide provides general diagnostic procedures for informational purposes. Always consult the official Hitachi service manual for your specific machine serial number and software version. If unfamiliar with electrical diagnostics or hydraulic systems, consult a certified Hitachi technician to prevent equipment damage or safety hazards.