Sumitomo SH350HD-6 Fault Code 117: Complete Diagnostic Guide

What is Sumitomo SH350HD-6 Fault Code 117?

Fault Code 117 on the Sumitomo SH350HD-6 excavator indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading detected by the Engine Control Module (ECM). This code specifically signals that the ECM has detected either an open circuit, short circuit, or implausible voltage signal from the coolant temperature sensor (also known as the water temperature sensor).

This diagnostic trouble code is critical for the SH350HD-6's performance because the ECM relies on accurate coolant temperature data to optimize fuel injection timing, regulate engine idle speed, and prevent overheating conditions. When this sensor circuit fails, the engine may operate inefficiently or enter protective derate mode to prevent catastrophic damage.

Common Symptoms

When Code 117 is active on your Sumitomo SH350HD-6, operators typically experience:

• Engine warning light illuminated on the instrument panel (amber or red depending on severity)
• Hard starting or extended cranking time, especially during cold weather conditions
• Rough idle or unstable engine RPM when the machine is warming up
• Reduced engine power or automatic derate as the ECM enters failsafe mode
• Cooling fan running continuously at high speed regardless of actual engine temperature

Potential Causes

The most common technical causes for Code 117 on used SH350HD-6 excavators include:

• Faulty coolant temperature sensor due to internal element degradation (common after 5,000+ operating hours)
• Damaged wiring harness between the sensor and ECM, particularly at rub points near the engine block mounting brackets
• Corroded or loose electrical connectors at the sensor plug—moisture intrusion is common in this location
• ECM internal fault affecting the sensor signal processing circuit (less common but possible in high-hour machines)
• Poor ground connection at the sensor circuit ground point on the engine block

How to Troubleshoot and Fix Code 117

Step 1: Visual Inspection Begin by locating the coolant temperature sensor on the engine block (typically near the thermostat housing). Inspect the sensor connector for corrosion, moisture, bent pins, or physical damage. Check the wiring harness from the sensor to the ECM for chafing, cuts, or evidence of rubbing against metal surfaces—common wear points on used excavators.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance. At 68°F (20°C), resistance should typically read between 2,000-3,000 ohms (consult your service manual for exact specifications). Test the harness continuity by checking resistance between the sensor connector pins and corresponding ECM terminals—readings should be less than 5 ohms.

Step 3: Voltage Signal Verification With the ignition on and sensor connected, backprobe the sensor connector to measure the reference voltage from the ECM (typically 5 volts). If voltage is absent or incorrect, suspect ECM issues or harness faults. For used excavators, carefully inspect all ground connections and clean any corrosion from terminals before replacing components.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine or OEM-equivalent coolant temperature sensor. Always apply dielectric grease to the new connector to prevent future moisture issues. Clear the fault code using diagnostic software and verify proper operation through a complete heat cycle.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Sumitomo service manual for your specific machine serial number and consider professional assistance from certified technicians for complex electrical diagnostics or ECM-related issues.