Sumitomo SH290-5 Fault Code 117: Complete Diagnostic Guide

What is Sumitomo SH290-5 Fault Code 117?

Fault Code 117 on the Sumitomo SH290-5 excavator indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading detected by the Electronic Control Module (ECM). This diagnostic trouble code (DTC) specifically monitors the voltage signal from the coolant temperature sensor (CTS), which provides critical data for engine performance, fuel injection timing, and overheat protection systems.

The ECM relies on accurate coolant temperature data to optimize engine efficiency and prevent thermal damage. On the Sumitomo SH290-5, this code typically triggers when the sensor voltage falls outside the manufacturer's specified range (usually 0.5-4.5 volts), indicating either a sensor failure, wiring issue, or actual overheating condition. This is particularly critical for the Isuzu 6WG1 engine commonly found in this model, as improper temperature readings can lead to incorrect fuel mapping and potential engine damage.

Common Symptoms

When Code 117 is active on your SH290-5, you may experience:

• Engine warning lamp illuminated on the instrument cluster (amber or red depending on severity)
• Engine derate or reduced power output as a protective measure
• Difficulty starting when the engine is cold, or rough idle conditions
• Cooling fan running continuously at maximum speed regardless of actual temperature
• Abnormal temperature gauge readings showing erratic fluctuations or stuck readings

Potential Causes

For used Sumitomo SH290-5 excavators, the following are the most common root causes:

• Faulty coolant temperature sensor – Internal resistance degradation is common after 5,000+ operating hours
• Damaged or corroded wiring harness – Particularly at connector pins near the thermostat housing where vibration and heat cause wire chafing
• Corroded or loose electrical connectors – The CTS connector is exposed to coolant mist and road debris, leading to oxidation
• ECM ground circuit issues – Poor chassis ground connections affect sensor voltage reference
• Actual engine overheating – Low coolant level, failed thermostat, or clogged radiator triggering legitimate high-temperature warnings
• Previous repair damage – Improper harness routing after engine work causing intermittent shorts

How to Troubleshoot and Fix Code 117

Step 1: Visual Inspection Begin with a thorough inspection of the coolant temperature sensor located near the thermostat housing on the engine block. Check for coolant leaks, corrosion on the two-pin connector, and physical damage to the sensor body. On used excavators, inspect the entire engine harness for signs of rubbing against the engine block, exhaust components, or hydraulic lines – a common failure point on machines with 3,000+ hours.

Step 2: Electrical Testing Disconnect the CTS connector and use a digital multimeter to measure sensor resistance. With the engine cold (approximately 68°F/20°C), resistance should read between 2,000-3,000 ohms. As temperature increases to operating range (180°F/82°C), resistance should drop to approximately 200-400 ohms. Compare your readings to the Sumitomo service manual specifications. Also check for continuity between sensor ground and chassis ground – resistance should be less than 1 ohm.

Step 3: Voltage Signal Check With the connector attached and ignition on (engine off), backprobe the signal wire at the ECM connector using your multimeter. You should see approximately 3-4 volts on a cold engine. If voltage reads 0V or 5V constantly, suspect wiring issues or ECM problems rather than sensor failure.

Step 4: Connector and Harness Repair Clean all connector pins with electrical contact cleaner and inspect for bent terminals. Apply dielectric grease to prevent future corrosion. For used machines, carefully inspect harness routing – reposition and secure any wires showing wear marks with proper heat-resistant loom and zip ties away from heat sources.

Step 5: Component Replacement If testing confirms sensor failure, replace with a genuine Sumitomo or OEM-equivalent coolant temperature sensor. After installation, clear the fault code using diagnostic software (Sumitomo proprietary software or compatible scan tool) and verify the code does not return after a complete heat cycle.

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Disclaimer: This guide provides general diagnostic information for the Sumitomo SH290-5. Always consult the manufacturer's service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs may cause additional damage or safety hazards.