Kobelco SK140LC-8 Fault Code 11108: Complete Diagnostic Guide

What is Kobelco SK140LC-8 Fault Code 11108?

Fault Code 11108 on the Kobelco SK140LC-8 excavator indicates a malfunction in the engine coolant temperature sensor circuit, specifically reporting an abnormally high voltage signal or open circuit condition.

This diagnostic trouble code (DTC) is generated when the Engine Control Module (ECM) detects voltage readings outside the acceptable range from the coolant temperature sensor. The coolant temperature sensor plays a critical role in engine management by providing real-time data that influences fuel injection timing, idle speed control, and overall engine performance optimization. On the SK140LC-8 with its Hino J05E engine, accurate coolant temperature monitoring is essential for preventing overheating and ensuring proper emissions control.

When this code activates, the ECM may default to a predetermined coolant temperature value, potentially affecting engine efficiency and protective shutdown functions.

Common Symptoms

• Check engine light or warning indicator illuminated on the instrument panel
• Engine running in derate mode with reduced power output to prevent potential damage
• Hard starting conditions, especially during cold weather operation
• Cooling fan running continuously at high speed regardless of actual engine temperature
• Erratic idle speed or poor throttle response during warm-up cycles

Potential Causes

The most common technical reasons for Code 11108 on used SK140LC-8 excavators include:

• Faulty coolant temperature sensor due to age-related degradation or internal element failure
• Damaged wiring harness between the sensor and ECM, particularly at known rub points near the engine mount brackets
• Corroded or loose connector terminals at the sensor plug, common in machines exposed to moisture
• Open circuit caused by broken wires within the harness insulation (often invisible externally)
• ECM internal fault affecting the sensor input circuit (rare but possible on high-hour machines)
• Poor ground connection at the sensor mounting point due to corrosion or loose hardware

How to Troubleshoot and Fix Code 11108

Step 1: Visual Inspection Begin by locating the coolant temperature sensor on the engine block (typically near the thermostat housing on the Hino J05E). Inspect the wiring harness for obvious damage, abrasion, or signs of heat damage. Check connector terminals for corrosion, bent pins, or moisture intrusion. On used excavators, pay special attention to harness routing where it may contact frame components.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure resistance across the sensor terminals. At room temperature (68°F/20°C), resistance should typically read between 2,000-3,000 ohms (consult Kobelco service manual for exact specifications). If readings show infinite resistance (open circuit) or zero ohms (short circuit), replace the sensor.

Step 3: Circuit Verification With the sensor disconnected, check voltage supply at the harness connector. You should measure approximately 5 volts reference voltage from the ECM. If voltage is absent or incorrect, trace the wiring back to the ECM, checking for breaks or shorts to ground. Inspect harness connectors for white/green corrosion buildup, common on machines operating in humid environments.

Step 4: Advanced Diagnostics If sensor and wiring test properly, connect Kobelco diagnostic software to monitor live sensor data. Compare actual coolant temperature (verified with infrared thermometer) against ECM-reported values. A discrepancy indicates ECM calibration issues or internal faults requiring dealer-level diagnostics.

Critical Note for Used Equipment: Before replacing components, thoroughly clean all ground connections and apply dielectric grease to connectors. Many intermittent codes on older machines resolve with proper connector maintenance.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Kobelco service manual for your specific machine serial number and production year. Complex electrical issues may require professional diagnosis with manufacturer-specific tools. Improper repairs can lead to engine damage or safety hazards.