Sumitomo SH300-6 Fault Code 113: Complete Diagnostic Guide

What is Sumitomo SH300-6 Fault Code 113?

Fault Code 113 on the Sumitomo SH300-6 excavator indicates a malfunction in the Engine Coolant Temperature (ECT) Sensor Circuit, specifically detecting an abnormal voltage signal or open circuit condition in the coolant temperature monitoring system. This diagnostic trouble code (DTC) is generated when the Engine Control Module (ECM) receives sensor readings outside the predetermined voltage range (typically 0.5V to 4.5V), suggesting either sensor failure or wiring issues.

This code is critical for the SH300-6's performance because the ECT sensor provides essential data for fuel injection timing, idle speed control, and engine protection protocols. When the ECM cannot accurately monitor coolant temperature, it defaults to "limp mode" parameters that can significantly reduce machine productivity and potentially cause long-term engine damage if overheating occurs undetected.

Common Symptoms

When Code 113 is active on your Sumitomo SH300-6, you may experience:

• Engine warning light illuminated on the instrument panel with possible audible alarm
• Hard starting or extended cranking time, especially in cold conditions
• Rough idle or erratic RPM fluctuations during warm-up
• Reduced engine power or activation of derate mode limiting maximum RPM
• Cooling fan running continuously at high speed regardless of actual engine temperature

Potential Causes

The most common technical reasons for Code 113 on used SH300-6 excavators include:

• Failed ECT sensor due to internal element degradation (common after 5,000+ operating hours)
• Damaged wiring harness at known rub points near the engine block mounting brackets
• Corroded or loose connector pins at the sensor plug or ECM connection
• Broken or frayed wires in the sensor circuit, particularly where the harness routes along the valve cover
• ECM internal fault (rare, but possible in high-hour machines)
• Coolant contamination on sensor terminals causing erratic resistance readings

How to Troubleshoot and Fix Code 113

Step 1: Visual Inspection Begin by locating the ECT sensor (typically installed in the engine block near the thermostat housing). Inspect the wiring harness for obvious damage, chafing, or oil contamination. On used excavators, pay special attention to areas where the harness contacts metal surfaces or heat shields. Check the connector for corrosion, bent pins, or coolant intrusion.

Step 2: Electrical Testing Using a digital multimeter (DMM), disconnect the ECT sensor connector and measure resistance across the sensor terminals. At room temperature (68°F/20°C), resistance should read approximately 2,000-3,000 ohms (consult your service manual for exact specifications). Test the wiring harness continuity from the sensor connector to the ECM, checking for open circuits or shorts to ground.

Step 3: Voltage Signal Verification With the ignition on and sensor connected, backprobe the sensor connector to measure voltage. You should see approximately 3-4V at cold temperatures, decreasing to 0.5-1.5V when warm. If voltage remains constant or reads 5V continuously, suspect an open circuit; 0V indicates a short to ground.

Step 4: Component Replacement and Verification If testing confirms sensor failure, replace the ECT sensor using OEM or quality aftermarket parts. For used machines, always apply dielectric grease to connector terminals to prevent future corrosion. After replacement, clear the fault code using diagnostic software (Sumitomo-compatible scan tool) and monitor for code recurrence during a complete heat cycle.

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Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Sumitomo service manual for your specific machine serial number. If you're unfamiliar with electrical diagnostics or working with pressurized cooling systems, seek assistance from a certified heavy equipment technician to avoid injury or further equipment damage.