What is Hyundai R385LVS Fault Code 111-2?

Fault Code 111-2 on the Hyundai R385LVS excavator indicates an Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage condition. This fault occurs when the Engine Control Module (ECM) detects an abnormally low voltage signal from the coolant temperature sensor circuit, typically below 0.2 volts. The ECT sensor is a critical component that monitors engine operating temperature and directly influences fuel injection timing, idle speed, and engine protection protocols.

This code is particularly important for the R385LVS because incorrect coolant temperature readings can cause improper fuel mapping, leading to poor combustion efficiency, increased emissions, and potential engine overheating without warning. The ECM relies on accurate temperature data to prevent thermal damage to the engine block and head gasket.

Common Symptoms

• Check Engine Light or malfunction indicator lamp illuminated on the dash panel
• Engine difficult to start, especially in cold conditions, or excessive cranking required
• Rough idle or unstable RPM fluctuations when the machine is warming up
• Cooling fan running continuously at high speed, even when engine temperature is normal
• Reduced engine power or derate mode activation, limiting hydraulic performance during demanding operations

Potential Causes

The most common technical causes for Code 111-2 on used Hyundai excavators include:

• Damaged or shorted ECT sensor wiring harness, particularly where the harness routes near sharp edges or moving components along the engine block
• Failed coolant temperature sensor with internal short circuit to ground
• Corroded or loose electrical connectors at the sensor or ECM side, common in machines exposed to muddy or wet job sites
• Damaged sensor ground circuit or poor chassis ground connection
• ECM internal fault (less common) affecting the sensor input circuit
• Previous repair attempts using non-OEM sensors with incorrect resistance specifications

How to Troubleshoot and Fix Code 111-2

Step 1: Visual Inspection Begin by locating the ECT sensor on the engine block (typically near the thermostat housing). Inspect the sensor connector for corrosion, bent pins, or moisture intrusion. Check the entire wiring harness from sensor to ECM for signs of chafing, especially where it contacts the engine or frame. On used excavators, harness rubbing is a frequent culprit.

Step 2: Electrical Testing Disconnect the ECT sensor connector. Using a digital multimeter, check for continuity between the sensor signal wire and ground—there should be infinite resistance (open circuit). If continuity exists, you have a short to ground in the harness. Next, measure sensor resistance: at 68°F (20°C), resistance should be approximately 2,500 ohms. Consult your service manual for exact specifications.

Step 3: Circuit Voltage Check With the ignition on and sensor disconnected, measure voltage at the ECM-side connector. You should see approximately 5 volts reference voltage. If voltage is absent, check for ECM power supply issues or damaged wiring between the ECM and sensor. If voltage is present but the code persists after reconnecting a known-good sensor, suspect ECM fault.

Step 4: Component Replacement and Verification Replace the ECT sensor with an OEM or quality aftermarket part. Ensure proper thread sealant application to prevent coolant leaks. Clear fault codes using Hyundai diagnostic software (Hi-MATE or compatible scan tool) and perform a test run under operating temperature. Monitor live data to confirm sensor readings match actual coolant temperature.

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

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Hyundai service manual for your specific machine serial number and seek professional diagnostic assistance if unfamiliar with electrical systems or if the fault persists after basic repairs.