What is Hitachi ZX350K-5G Fault Code 14107-2?

Fault Code 14107-2 indicates a malfunction in the Engine Coolant Temperature (ECT) Sensor Circuit - specifically a voltage signal that is too high or out of normal operating range. This diagnostic trouble code (DTC) is generated when the Engine Control Module (ECM) detects an abnormally high voltage reading from the coolant temperature sensor, typically above 4.5 volts when normal operating range should be between 0.5-4.0 volts.

This code is critical for the ZX350K-5G because the ECT sensor provides essential data that the ECM uses to control fuel injection timing, throttle response, and cooling fan operation. When this sensor reports incorrect data, the engine cannot optimize performance, potentially leading to poor fuel economy, increased emissions, and possible engine damage from overheating conditions that go undetected.

Common Symptoms

• Engine warning light illuminated on the instrument cluster, often accompanied by a "Check Engine" message on the monitor display
• Engine derate mode activated, limiting maximum RPM to protect the engine from potential thermal damage
• Cooling fan running continuously at high speed, even when engine temperature is normal
• Hard starting or rough idle, especially during cold starts, as the ECM defaults to a predetermined temperature value
• Black smoke from exhaust due to incorrect fuel mixture calculations based on faulty temperature readings

Potential Causes

The most common causes of fault code 14107-2 on used ZX350K-5G excavators include:

Damaged or corroded wiring harness - particularly where the sensor harness runs near the engine block or exhaust manifold, common rub points for this model. Open circuit conditions caused by broken wires inside the insulation create high voltage readings.

Failed ECT sensor - internal sensor element degradation is common in machines with 5,000+ operating hours, causing erratic resistance values.

Corroded or loose connector pins at the sensor connection point - moisture intrusion and vibration over years of operation frequently cause poor connections.

ECM internal fault - less common but possible in older units, where the voltage reference circuit inside the Engine Control Module develops issues.

Aftermarket sensor incompatibility - if the excavator previously had repairs using non-OEM sensors, resistance curves may not match Hitachi specifications.

How to Troubleshoot and Fix Code 14107-2

Step 1: Visual Inspection Begin by locating the ECT sensor (typically mounted on the engine coolant outlet housing near the thermostat). Inspect the sensor connector for corrosion, bent pins, or moisture. Check the wiring harness from sensor to ECM for abrasion, particularly where it passes near hot exhaust components or sharp metal edges - a known wear point on ZX350K-5G models.

Step 2: Electrical Testing Disconnect the ECT sensor connector. Using a digital multimeter, measure resistance across the sensor terminals. At 68°F (20°C), resistance should read approximately 2,400-2,700 ohms; at 176°F (80°C), approximately 300-330 ohms. If readings are infinite (open circuit) or zero (short circuit), replace the sensor. Also check for voltage supply at the harness connector - you should see approximately 5 volts reference voltage from the ECM with ignition on.

Step 3: Harness Continuity Check With the sensor disconnected and ignition off, check continuity between the sensor harness connector and the ECM connector pins (consult service manual for specific pin locations). Resistance should be less than 1 ohm. For used excavators, pay special attention to harness sections that show heat discoloration or previous repair attempts with electrical tape.

Step 4: Clear Code and Monitor After repairs, clear the fault code using Hitachi Dr.EX diagnostic software or a compatible scan tool. Run the engine through multiple temperature cycles while monitoring live data. If code returns, suspect ECM issues or intermittent harness faults requiring more extensive diagnosis.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Hitachi service manual for your specific machine serial number. If unfamiliar with electrical diagnostics or heavy equipment systems, contact a certified Hitachi technician to prevent further damage or safety hazards.