Hitachi ZH200LC-5A Fault Code 20107-2: Complete Diagnostic Guide

What is Hitachi ZH200LC-5A Fault Code 20107-2?

Fault Code 20107-2 indicates a malfunction in the engine coolant temperature sensor circuit, specifically detecting an abnormal voltage signal or intermittent connection in the cooling system monitoring circuit. This code is triggered when the Engine Control Module (ECM) receives voltage readings outside the predetermined range for the coolant temperature sensor, typically indicating either an open circuit, short circuit, or sensor degradation.

This fault is critical for the ZH200LC-5A because the ECM relies on accurate coolant temperature data to optimize fuel injection timing, control engine warm-up cycles, and prevent overheating damage. Ignoring this code can lead to poor fuel economy, increased emissions, and potential engine damage from inadequate thermal management.

Common Symptoms

When fault code 20107-2 is active, operators typically experience:

• Check Engine Light or warning lamp illuminated on the instrument cluster
• Erratic temperature gauge readings or gauge stuck at minimum/maximum positions
• Engine running in limp mode with reduced power output to prevent thermal damage
• Difficulty starting when the engine is cold, or excessive white smoke during warm-up
• Cooling fans running continuously at maximum speed regardless of actual engine temperature

Potential Causes

The most common technical causes for this fault code on used ZH200LC-5A excavators include:

• Coolant temperature sensor failure due to age-related degradation or thermal cycling stress
• Corroded or damaged wiring harness connectors at the sensor connection point
• Chafed or broken wires in the harness, particularly where it routes near the engine block or frame rails (known wear point on this model)
• Contaminated sensor tip from coolant additives or debris in older cooling systems
• ECM internal circuit failure (less common but possible in high-hour machines)
• Poor ground connection at the sensor mounting location due to corrosion buildup

How to Troubleshoot and Fix Code 20107-2

Step 1: Visual Inspection Begin by locating the coolant temperature sensor on the engine block (typically near the thermostat housing). Inspect the sensor connector for corrosion, moisture intrusion, or damaged pins. On used excavators, check the entire wiring harness route for signs of rubbing, heat damage, or previous repairs.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. At room temperature (20°C), resistance should typically read 2,000-3,000 ohms (consult service manual for exact specifications). Test harness continuity from the sensor connector back to the ECM and verify ground circuit integrity.

Step 3: Live Data Analysis Connect Hitachi diagnostic software (Dr.EX or compatible scan tool) and monitor live coolant temperature readings. Compare sensor voltage output against actual engine temperature using an infrared thermometer. Voltage should decrease smoothly as temperature rises (typically 4.5V cold to 0.5V hot).

Step 4: Component Replacement If sensor readings are erratic or out of specification, replace the coolant temperature sensor using OEM or quality aftermarket parts. Before installation, clean the mounting boss thoroughly and apply appropriate thread sealant. Clear codes and perform a test cycle.

For used excavators, always inspect connector terminals for corrosion and apply dielectric grease during reassembly to prevent future moisture issues.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Hitachi service manual for your specific machine serial number and seek professional assistance from certified technicians for complex repairs or if you're uncertain about any procedure.