What is Hyundai R385LVS Fault Code 110-3?

Fault Code 110-3 on the Hyundai R385LVS excavator indicates an Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage condition. This diagnostic trouble code signals that the Engine Control Module (ECM) has detected sporadic high voltage readings from the coolant temperature sensor circuit, typically exceeding 4.8-5.0 volts when normal operating range should be between 0.5-4.5 volts.

This code is critical for the R385LVS because the ECT sensor directly influences fuel injection timing, engine warm-up procedures, and cooling fan operation. The Cummins QSX15 engine in this excavator relies heavily on accurate coolant temperature data to prevent overheating and optimize performance. Intermittent readings can cause the ECM to receive conflicting data, leading to improper engine protection strategies and reduced machine efficiency.

Common Symptoms

• Engine warning light illuminates on the instrument cluster, often intermittently
• Hard starting conditions when the engine is cold, as the ECM miscalculates warm-up enrichment
• Cooling fan runs constantly at high speed, even when engine temperature is normal
• Engine power derate may occur if the ECM enters failsafe mode, limiting RPM to 1500-1800
• Erratic temperature gauge readings that fluctuate unexpectedly during operation

Potential Causes

The intermittent nature of code 110-3 typically points to connection and wiring issues rather than sensor failure. In used R385LVS machines, common causes include:

• Corroded or loose connector pins at the ECT sensor (located near the thermostat housing on the engine's right side)
• Wiring harness chafing against engine block or brackets, creating intermittent open circuits
• Moisture intrusion in the sensor connector from damaged weather seals
• Failed ECT sensor with internal intermittent open circuit (less common but possible after 8,000+ hours)
• ECM internal circuit degradation (rare, but verify after eliminating all other causes)
• Poor ground connections at engine block grounding points affecting sensor reference voltage

How to Troubleshoot and Fix Code 110-3

Step 1: Visual Inspection and Connector Check Begin by locating the ECT sensor on the engine block near the thermostat housing. Disconnect the two-pin connector and inspect for corrosion, bent pins, or moisture. Clean contacts with electrical contact cleaner and check the connector locking mechanism. On used excavators, this connector often shows green corrosion due to coolant vapor exposure.

Step 2: Sensor and Circuit Testing Using a digital multimeter (DMM), measure the resistance across the sensor terminals. At 68°F (20°C), resistance should read approximately 2,200-2,800 ohms; at 176°F (80°C), approximately 270-380 ohms. If readings are out of specification or show infinite resistance intermittently, replace the sensor (Hyundai part# 21050-HK002 or equivalent).

Step 3: Wiring Harness Verification With the sensor disconnected, check for harness integrity by measuring resistance from each sensor wire back to the ECM connector (should read less than 5 ohms). Inspect the entire harness routing for chafe points, particularly where it passes near the exhaust manifold and engine mounts. Wiggle the harness while monitoring resistance—any fluctuation confirms intermittent connection. Check supply voltage at the sensor connector with ignition on: should read 5.0 volts ±0.1V.

Step 4: Ground Circuit and ECM Testing Verify the sensor ground circuit has less than 0.1 volts drop to battery negative. If all tests pass but code persists, suspect ECM internal fault. Use Hyundai Hi-MATE diagnostic software to monitor live ECT voltage data while inducing vibration—intermittent spikes above 4.9V confirm the issue.

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Disclaimer: This guide provides general troubleshooting information for educational purposes. Always consult the Hyundai R385LVS service manual and consider engaging a certified heavy equipment technician for diagnosis and repair, especially when working with engine management systems.