What is Hitachi ZX210H-5G-HCMC Fault Code 14105-2?

Fault Code 14105-2 indicates a malfunction in the engine coolant temperature sensor circuit, specifically a voltage signal that is too high or an open circuit condition detected by the Engine Control Module (ECM). This code is part of Hitachi's advanced diagnostic system for the ZX210H-5G hydraulic excavator equipped with Isuzu engine technology.

The coolant temperature sensor plays a critical role in engine management by monitoring operating temperatures and sending voltage signals to the ECM. When the ECM detects an abnormally high voltage (typically above 4.5V) or an open circuit, it triggers code 14105-2. This sensor directly affects fuel injection timing, idle speed control, and engine protection systems. For used excavators like the ZX210H-5G-HCMC, this fault can lead to improper fuel mapping, increased emissions, and potential engine damage if ignored.

Common Symptoms

• Engine warning lamp illuminated on the instrument cluster with possible derate mode activation
• Hard starting or extended cranking time, especially when the engine is cold
• Rough idle or hunting RPM as the ECM defaults to preprogrammed temperature values
• Black smoke from the exhaust due to improper fuel-air mixture calculations
• Cooling fan running continuously at high speed regardless of actual engine temperature

Potential Causes

The most common technical causes for code 14105-2 on used Hitachi excavators include:

• Damaged or corroded sensor connector at the coolant temperature sensor (common wear point near the thermostat housing)
• Open circuit in the wiring harness between the sensor and ECM, often caused by harness chafing against the engine block or frame
• Failed coolant temperature sensor with internal circuit breakdown (typical after 5,000+ operating hours)
• ECM ground circuit issues causing voltage reference problems
• Coolant contamination or low coolant levels causing sensor exposure to air pockets
• Previous repair attempts with incorrect sensor specifications or aftermarket parts

How to Troubleshoot and Fix Code 14105-2

Step 1: Visual Inspection Begin by locating the coolant temperature sensor (typically mounted on the engine cylinder head or thermostat housing). Inspect the sensor connector for corrosion, bent pins, moisture intrusion, or damaged seals. On used excavators, pay special attention to connector lock integrity and rubber boot condition, as these commonly deteriorate over time.

Step 2: Electrical Testing Disconnect the sensor and use a digital multimeter to measure resistance across the sensor terminals. At 20°C (68°F), resistance should typically read 2,000-3,000 ohms (consult your service manual for exact specifications). Next, check for voltage supply at the harness connector with the ignition on—you should see approximately 5V reference voltage from the ECM.

Step 3: Harness and Ground Verification Trace the wiring harness from the sensor to the ECM, checking for abrasion points, especially where the harness contacts metal surfaces or passes through bulkheads. Test continuity through each wire and verify the ground circuit has less than 0.5 ohms resistance to chassis ground.

Step 4: Component Replacement If testing confirms sensor failure, replace with an OEM or equivalent sensor matching Hitachi part specifications. For used machines, always apply dielectric grease to connector terminals before reassembly to prevent future corrosion. Clear the fault code using Hitachi diagnostic software (Dr.EX) or a compatible scan tool, then monitor for code recurrence during a complete heat cycle.

Disclaimer: This guide provides general diagnostic information. Always consult the official Hitachi service manual for your specific machine serial number and consider professional diagnosis for complex electrical issues or if you're unfamiliar with high-voltage systems.