What is Hyundai R335LC-9T Fault Code 110-16?

Fault Code 110-16 indicates an Engine Coolant Temperature (ECT) Sensor Circuit High Voltage condition in the Hyundai R335LC-9T excavator's Electronic Control Module (ECM). This diagnostic trouble code (DTC) is triggered when the ECM detects an abnormally high voltage signal from the engine coolant temperature sensor, typically exceeding the manufacturer's specified threshold of approximately 4.8-5.0 volts.

This code is critical for the R335LC-9T because the ECT sensor provides essential data that the ECM uses to manage fuel injection timing, engine warm-up cycles, and cooling fan operation. When this sensor circuit reports high voltage, the ECM cannot accurately determine actual engine temperature, potentially leading to improper fuel mapping, reduced engine protection, and performance issues. In Hyundai's latest generation excavators like the -9T series, this can also affect diesel exhaust fluid (DEF) system operation and diesel particulate filter (DPF) regeneration cycles.

Common Symptoms

• Engine warning light or check engine light illuminated on the instrument cluster
• Hard starting when the engine is cold, as the ECM defaults to a failsafe temperature value
• Cooling fan running continuously at high speed, even when engine is cold
• Reduced engine power or derate mode activation to protect the engine from potential overheating
• Poor fuel economy and rough idle due to incorrect fuel-air mixture calculations

Potential Causes

The most common technical causes for Code 110-16 on used R335LC-9T excavators include:

• Open circuit in the ECT sensor wiring harness, often caused by wire breakage near the engine block mounting points where vibration stress is highest
• Failed ECT sensor with internal open circuit condition (common after 5,000-8,000 operating hours)
• Corroded or damaged connector pins at the sensor or ECM connection points, particularly on machines operated in wet or coastal environments
• Chafed wiring harness where the engine harness routes along the valve cover—a known wear point on R335LC-9T models
• Poor ground connection at the sensor ground circuit or ECM ground points
• ECM internal fault (rare, but possible on older used machines with 10,000+ hours)

How to Troubleshoot and Fix Code 110-16

Step 1: Visual Inspection Begin by inspecting the ECT sensor and its wiring harness for obvious damage. The sensor is typically located on the engine cylinder head or thermostat housing. Check for coolant leaks around the sensor, corroded connectors, or damaged wires. On used excavators, pay special attention to harness routing near the exhaust manifold where heat damage commonly occurs.

Step 2: Electrical Testing Using a digital multimeter (DMM), disconnect the ECT sensor connector and measure resistance across the sensor terminals. At 68°F (20°C), resistance should be approximately 2,000-3,000 ohms (consult the Hyundai service manual for exact specifications). Next, check for continuity between the sensor connector and the ECM connector—there should be less than 1 ohm resistance. Check for voltage at the sensor connector with the key on, engine off; you should see approximately 5 volts reference voltage from the ECM.

Step 3: Circuit and Ground Verification Inspect the sensor ground circuit by measuring voltage drop between the sensor ground pin and battery negative while cranking the engine—it should be less than 0.1 volts. Check the wiring harness for shorts to power by measuring resistance between the signal wire and battery positive (should be infinite resistance/open circuit).

Step 4: Component Replacement and Verification If testing reveals an open circuit or the sensor resistance is out of specification, replace the ECT sensor with a genuine Hyundai or OEM-equivalent part. For used excavators with over 5,000 hours, also inspect and clean all connector pins with electrical contact cleaner and apply dielectric grease. After replacement, clear the fault code using Hi-ScanPro or compatible diagnostic software and verify the repair by monitoring live coolant temperature data during a complete warm-up cycle.

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Disclaimer: This guide provides general troubleshooting information for educational purposes. Always consult the official Hyundai service manual for your specific machine serial number and seek assistance from a qualified heavy equipment technician for complex electrical diagnostics or repairs. Improper repairs may void warranties or cause equipment damage.