What is Hitachi ZX210LCH-5G Fault Code 43?

Fault Code 43 on the Hitachi ZX210LCH-5G indicates a malfunction in the Engine Coolant Temperature (ECT) sensor circuit. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects an abnormal voltage signal from the coolant temperature sensor, typically indicating an open circuit, short circuit, or sensor reading outside the acceptable range.

The ECT sensor plays a critical role in engine management by monitoring coolant temperature and sending voltage signals to the ECM. This data controls fuel injection timing, idle speed, and engine warm-up cycles. On used excavators like the ZX210LCH-5G, this sensor is essential for preventing overheating and maintaining optimal combustion efficiency. When Code 43 appears, the ECM enters a fail-safe mode, potentially affecting engine performance and fuel economy.

Common Symptoms

When Fault Code 43 is active on your Hitachi ZX210LCH-5G, operators typically experience:

• Check Engine Light or malfunction indicator lamp illuminated on the instrument panel
• Hard starting or rough idle, especially when the engine is cold
• Poor fuel economy due to incorrect fuel mixture calculations
• Engine overheating or failure to reach normal operating temperature
• Black smoke from the exhaust during acceleration or under load

Potential Causes

Several technical issues can trigger Code 43 on used excavators:

• Faulty ECT sensor – Internal resistance failure is common in high-hour machines (sensor typically reads -40°F or 300°F+ when failed)
• Damaged wiring harness – Chafing or rubbing near the engine block mounting points, particularly where the harness passes near the fuel injection pump
• Corroded or loose electrical connectors – Water intrusion at the sensor connector (common on machines operating in wet conditions)
• Poor ground connection – Corrosion at the engine ground strap connection points
• ECM internal fault – Rare, but possible on high-hour machines with previous electrical issues

How to Troubleshoot and Fix Code 43

Step 1: Visual Inspection Begin by inspecting the ECT sensor located on the engine block near the thermostat housing. Check for physical damage, coolant leaks around the sensor base, and corrosion on the electrical connector. On used excavators, inspect the wiring harness from the sensor to the ECM for wear points, particularly where it contacts the engine or frame.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance. At room temperature (68°F/20°C), the sensor should read approximately 2,000-3,000 ohms. Next, check for supply voltage at the connector with the ignition on – you should see approximately 5 volts from the ECM. Test for continuity between the sensor ground and chassis ground.

Step 3: Advanced Diagnostics If resistance and voltage are correct, perform a live data scan using Hitachi diagnostic software (Dr.EX or compatible tool). Monitor the ECT sensor temperature reading while the engine warms up – it should rise gradually from ambient to 180-200°F. Erratic readings or sudden jumps indicate internal sensor failure. For used machines, always inspect connector terminals for corrosion and apply dielectric grease before reassembly.

Step 4: Component Replacement Replace the ECT sensor if readings are out of specification (typical part number: 4621617 or equivalent). After installation, clear the fault code using diagnostic software and verify the code doesn't return after a complete warm-up cycle.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Hitachi service manual for your specific machine serial number and consider professional diagnostic assistance for complex electrical issues. Improper repairs may void warranties or cause additional damage.