Sumitomo SH350HD-5 Fault Code 113: Complete Diagnostic Guide

What is Sumitomo SH350HD-5 Fault Code 113?

Fault Code 113 on the Sumitomo SH350HD-5 excavator indicates an Engine Coolant Temperature (ECT) Sensor Circuit High Voltage condition. This diagnostic trouble code triggers when the Engine Control Module (ECM) detects an abnormally high voltage signal from the coolant temperature sensor circuit, typically above 4.8-5.0 volts.

The ECT sensor plays a critical role in the SH350HD-5's Isuzu engine management system by monitoring coolant temperature and providing data for fuel injection timing, idle speed control, and engine protection protocols. When the ECM receives incorrect temperature readings, it cannot properly regulate engine performance, potentially leading to inefficient combustion, increased emissions, and inadequate engine protection against overheating.

Common Symptoms

When Code 113 is active on your SH350HD-5, you may experience:

• Engine warning light illuminated on the instrument cluster (amber or red depending on severity)
• Hard starting conditions, especially when the engine is cold, due to improper fuel enrichment
• Rough idle or hunting RPM as the ECM compensates for perceived temperature variations
• Cooling fan running continuously at high speed, even when engine is cold
• Reduced engine power or activation of derate mode as a protective measure
• Inaccurate temperature gauge readings, often showing full cold or fluctuating erratically

Potential Causes

The most common technical causes for Code 113 on used SH350HD-5 excavators include:

• Open circuit in ECT sensor wiring harness due to wire breakage or connector damage
• Failed ECT sensor with internal open circuit (common failure mode after 5,000+ operating hours)
• Corroded or loose connector terminals at the sensor or ECM connection points
• Damaged sensor harness from rubbing against engine components or heat exposure near exhaust manifold
• ECM internal fault (less common) affecting the sensor circuit voltage reference
• Aftermarket sensor incompatibility if previous repairs used non-OEM parts

How to Troubleshoot and Fix Code 113

Step 1: Visual Inspection Begin by locating the ECT sensor on the engine block (typically near the thermostat housing on Isuzu engines). Inspect the sensor connector for corrosion, bent pins, moisture intrusion, or physical damage. On used excavators, check the entire wiring harness from sensor to ECM for chafing, particularly where it routes near moving components or heat sources.

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. Compare readings against the manufacturer's temperature-resistance chart. If the sensor shows infinite resistance (open circuit) or values outside specifications, replacement is required.

Step 3: Circuit Continuity Check With the sensor disconnected, check for continuity between the sensor harness connector and the ECM connector using a wiring diagram. Measure voltage at the harness connector with ignition on—you should see approximately 5 volts reference voltage from the ECM. If voltage reads near battery voltage (12V+), there's likely an open ground circuit in the sensor return wire.

Step 4: Connector Service and Replacement Clean all connector terminals with electrical contact cleaner and apply dielectric grease to prevent future corrosion—critical for used machines operating in harsh environments. If harness damage is found, repair using heat-shrink solder connections rather than crimp connectors for durability.

Step 5: Clear Code and Verify After repairs, clear the fault code using Sumitomo diagnostic software or a compatible OBD scanner. Monitor live coolant temperature data during warm-up to verify proper sensor operation and confirm the code doesn't return.

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Professional Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Sumitomo SH350HD-5 service manual for model-specific procedures, torque specifications, and safety protocols. If you lack proper diagnostic tools or experience with heavy equipment electrical systems, consult a certified Sumitomo technician to prevent misdiagnosis or damage to the ECM.