Sumitomo SH350HD-6 Fault Code 1113: Expert Diagnostic Guide

What is Sumitomo SH350HD-6 Fault Code 1113?

Fault Code 1113 on the Sumitomo SH350HD-6 indicates a malfunction in the Engine Coolant Temperature (ECT) Sensor Circuit, specifically reporting an abnormally high voltage signal or open circuit condition. This code is triggered when the Engine Control Module (ECM) detects a voltage reading outside the normal operating range (typically above 4.5 volts) from the coolant temperature sensor circuit.

The ECT sensor plays a critical role in the SH350HD-6's engine management system by monitoring coolant temperature and providing data that directly influences fuel injection timing, idle speed control, and diagnostic system operations. When this sensor circuit fails, the ECM cannot accurately assess engine thermal conditions, potentially leading to improper fuel delivery, increased emissions, and reduced operational efficiency in this 35-ton class excavator.

Common Symptoms

When Code 1113 is active on your Sumitomo SH350HD-6, operators typically experience:

• Check Engine Light or malfunction indicator lamp illuminated on the instrument cluster
• Engine may run in limp mode with reduced power output and limited RPM range
• Difficulty starting when the engine is cold, or extended cranking times
• Cooling fan running continuously at high speed regardless of actual engine temperature
• Erratic idle speed or rough running conditions, particularly during warm-up cycles

Potential Causes

The most common technical reasons for Code 1113 appearing on used SH350HD-6 excavators include:

• Open circuit in the ECT sensor wiring harness, often caused by wire breakage near flex points around the engine block
• Failed coolant temperature sensor with internal resistance breakdown (common after 5,000+ operating hours)
• Corroded or loose connector pins at the sensor or ECM connection points—particularly vulnerable to moisture intrusion
• Damaged wiring insulation due to rubbing against engine components or heat degradation near exhaust manifolds
• ECM internal fault affecting the sensor input circuit (less common but possible in high-hour machines)
• Improper previous repairs using incorrect sensor specifications or aftermarket components

How to Troubleshoot and Fix Code 1113

Step 1: Visual Inspection Begin by inspecting the ECT sensor located on the engine block (typically near the thermostat housing). Check for physical damage, coolant leaks around the sensor base, and examine the wiring harness for obvious breaks, burns, or abrasion damage. On used excavators, pay special attention to harness routing where it passes near moving components or hot surfaces.

Step 2: Connector and Resistance Testing Disconnect the ECT sensor connector and inspect both the sensor and harness-side terminals for corrosion, bent pins, or moisture contamination. Using a digital multimeter, measure the sensor's resistance between its terminals. At room temperature (68°F/20°C), resistance should typically read between 2,000-3,000 ohms (consult your service manual for exact specifications). Replace the sensor if readings are infinite (open circuit) or significantly outside specifications.

Step 3: Circuit Voltage and Continuity Checks With the sensor disconnected and ignition ON (engine OFF), measure voltage at the harness connector. You should see approximately 5 volts on the signal wire (reference voltage from ECM). If voltage is absent or incorrect, check for open circuits or shorts in the wiring between the sensor and ECM. Test continuity of the ground circuit as well. For used machines, remove wire loom coverings to inspect for hidden damage caused by years of vibration and thermal cycling.

Step 4: Clear Code and Verify Repair After repairs, clear the fault code using Sumitomo diagnostic software or a compatible scan tool. Run the engine through complete warm-up cycles while monitoring live coolant temperature data to ensure the sensor responds correctly and the code does not return.

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Disclaimer: This guide provides general troubleshooting information for Code 1113. Always consult the official Sumitomo service manual for your specific machine serial number. If you're uncomfortable performing electrical diagnostics, contact a certified Sumitomo technician or qualified heavy equipment mechanic to prevent further damage to your excavator's systems.