Hyundai R225LVS Fault Code 111-3: Complete Diagnostic Guide

What is Hyundai R225LVS Fault Code 111-3?

Fault Code 111-3 on the Hyundai R225LVS excavator indicates an Engine Coolant Temperature (ECT) Sensor Circuit Intermittent Signal or abnormal voltage reading detected by the Engine Control Module (ECM).

This diagnostic trouble code (DTC) is triggered when the ECM receives erratic or out-of-range voltage signals from the coolant temperature sensor, typically classified as a warning-level fault. The ECT sensor plays a critical role in engine performance by monitoring coolant temperature and relaying data to the ECM for fuel injection timing, idle speed control, and emissions management. On used excavators like the R225LVS, this code often indicates deteriorating electrical connections or sensor degradation rather than complete failure, making intermittent detection common during startup or temperature fluctuations.

Common Symptoms

When Code 111-3 is active on your Hyundai R225LVS, operators typically experience:

• Check Engine Light (CEL) or malfunction indicator lamp illuminated on the instrument cluster
• Erratic engine idle or rough running, especially during cold starts
• Hard starting conditions in cold weather due to incorrect fuel mapping
• Radiator cooling fan running constantly or at abnormal intervals
• Reduced engine performance or hesitation under load as the ECM defaults to failsafe temperature values

Potential Causes

The most common technical reasons for Code 111-3 on used R225LVS excavators include:

• Corroded or loose wiring connections at the ECT sensor harness connector (common wear point on older machines)
• Damaged sensor harness from rubbing against engine components or heat exposure near the exhaust manifold
• Failing ECT sensor with internal resistance degradation causing intermittent signal loss
• Water intrusion into connector terminals from pressure washing or coolant system leaks
• Poor ground connection at the ECM or engine block grounding points
• ECM software glitches or internal controller faults (rare, but possible on high-hour machines)

How to Troubleshoot and Fix Code 111-3

Step 1: Visual Inspection Begin with a thorough inspection of the ECT sensor located on the engine block (typically near the thermostat housing). Check the wiring harness for visible damage, chafing, or contact with hot engine surfaces. On used excavators, examine connector terminals for corrosion, bent pins, or moisture. Clean connections with electrical contact cleaner and apply dielectric grease.

Step 2: Electrical Testing Using a digital multimeter (DMM), disconnect the ECT sensor connector and measure sensor resistance. At room temperature (68°F/20°C), expect approximately 2,000-3,000 ohms; resistance should decrease as temperature increases. Compare readings to Hyundai's specification chart. Check harness continuity between the sensor connector and ECM pins (consult wiring diagrams). Test for voltage supply from the ECM (typically 5V reference voltage).

Step 3: Component Replacement and Verification If sensor resistance is out of specification or harness shows intermittent continuity, replace the ECT sensor (OEM part recommended for reliability). For harness damage, repair using heat-shrink solder connectors or replace the affected section. After repairs, clear codes using Hyundai diagnostic software or compatible scan tool, operate the machine through full temperature cycles, and monitor for code recurrence.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Hyundai service manual for your specific machine serial number and consider professional diagnostic services for complex electrical issues or if you're uncertain about procedures.