What is Sumitomo SH350HD-6 Fault Code 113?

Fault Code 113 on the Sumitomo SH350HD-6 excavator indicates an Engine Coolant Temperature (ECT) Sensor Circuit High Voltage condition. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects an abnormally high voltage signal from the coolant temperature sensor circuit, typically reading above 4.8-4.9 volts when normal operating range should be 0.5-4.5 volts.

This code is critical for the SH350HD-6 because the ECT sensor provides essential data that the ECM uses to regulate fuel injection timing, idle speed, and engine protection protocols. When this sensor circuit fails high, the ECM cannot accurately monitor engine temperature, potentially leading to overheating damage or improper engine performance. The Isuzu engine powering this excavator relies heavily on precise temperature readings for optimal combustion efficiency and component longevity.

Common Symptoms

• Check Engine Light illuminated on the operator display panel with code 113 stored in ECM memory
• Engine may run in derate mode or limp mode, limiting RPM and hydraulic performance to prevent potential damage
• Hard starting conditions, especially when the engine is cold, due to incorrect fuel mixture calculations
• Engine may run excessively rich or lean, causing black smoke or rough idle
• Cooling fan may run continuously at high speed as the ECM defaults to maximum cooling protection mode

Potential Causes

The high voltage reading for Code 113 typically indicates an open circuit condition rather than a short to ground. Common causes on used SH350HD-6 excavators include:

• Broken or disconnected wiring in the ECT sensor harness, particularly near the engine block where vibration and heat cycles cause wire fatigue
• Corroded or loose connector pins at the sensor plug or ECM connection points—especially common in machines with high hours in wet or dusty environments
• Failed ECT sensor with internal open circuit (though less common than wiring issues when voltage reads high)
• Damaged ECM connector terminals or internal ECM circuit failure (rare but possible on high-hour machines)
• Chafed wiring harness where the sensor wire bundle rubs against the engine block, valve cover, or hydraulic lines over time

How to Troubleshoot and Fix Code 113

Step 1: Visual Inspection Begin with a thorough inspection of the ECT sensor and its wiring harness. The sensor is typically located on the engine block near the thermostat housing. Check for obvious damage, corroded connectors, or loose connections. On used excavators, pay special attention to harness routing where wires may have rubbed through insulation against metal surfaces—this is a frequent failure point on the SH350HD-6.

Step 2: Electrical Testing Disconnect the ECT sensor connector and use a digital multimeter to measure resistance across the sensor terminals. At room temperature (68°F/20°C), resistance should read approximately 2,000-3,000 ohms depending on exact temperature. If the reading shows infinite resistance (open circuit), replace the sensor. Also inspect connector pins for corrosion or bent terminals that prevent proper contact.

Step 3: Circuit Continuity Check With the sensor disconnected, check continuity and resistance from the sensor connector back to the ECM connector. You should have continuity on the signal wire and proper ground connection. Measure voltage at the sensor connector with ignition on—you should see approximately 5 volts reference voltage from the ECM. If voltage is present but disappears when the sensor is connected, the sensor is likely failed internally.

Step 4: Advanced Diagnostics If wiring and sensor test good, use Sumitomo diagnostic software or compatible scan tool to monitor live ECT sensor data. Compare readings with actual engine temperature using an infrared thermometer. On used machines, also check the ECM ground connections at the engine block, as corroded grounds can cause erratic sensor readings.

Disclaimer: This guide provides general troubleshooting information. Always consult the Sumitomo SH350HD-6 service manual for model-specific procedures and safety precautions. If you're uncomfortable performing electrical diagnostics, contact a certified Sumitomo technician or qualified heavy equipment mechanic.