What is Sumitomo SH290-5 Fault Code 107?

Fault Code 107 on the Sumitomo SH290-5 excavator indicates a malfunction in the Engine Coolant Temperature (ECT) Sensor circuit, specifically detecting an abnormally high voltage signal or open circuit condition. This code is triggered when the Engine Control Module (ECM) receives a voltage reading outside the normal operating range (typically above 4.5V) from the coolant temperature sensor circuit.

The ECT sensor plays a critical role in the SH290-5's engine management system by monitoring coolant temperature and sending real-time data to the ECM. This information directly affects fuel injection timing, idle speed control, and engine protection protocols. When Code 107 appears, the ECM cannot accurately assess engine temperature, potentially leading to improper fuel delivery, difficulty starting in cold conditions, and risk of engine overheating without proper warning systems functioning correctly.

Common Symptoms

When Fault Code 107 is active on your Sumitomo SH290-5, operators typically experience:

• Check Engine Light or malfunction indicator lamp illuminated on the instrument panel
• Hard starting conditions, especially when the engine is cold, due to incorrect fuel enrichment calculations
• Erratic idle speed or hunting RPM as the ECM compensates for missing temperature data
• Cooling fan running continuously at maximum speed, regardless of actual engine temperature
• Reduced engine power or derate mode activation as a protective measure against potential overheating

Potential Causes

Several factors can trigger Code 107 on used Sumitomo excavators:

• Open circuit or broken wiring in the ECT sensor harness, particularly common where the wire bundle passes near the engine block or exhaust manifold
• Failed ECT sensor with internal resistance breakdown (typical in machines with 8,000+ operating hours)
• Corroded or loose electrical connectors at the sensor or ECM interface—especially prevalent in excavators operated in wet or marine environments
• Damaged sensor harness from rubbing against engine components, a known issue near the thermostat housing on SH290-5 models
• ECM internal circuit fault (rare, but possible in older machines with moisture intrusion into the controller)

How to Troubleshoot and Fix Code 107

Step 1: Visual Inspection and Connector Check

Begin by locating the ECT sensor on the engine block (typically near the thermostat housing). Inspect the sensor connector for corrosion, bent pins, or moisture contamination. Disconnect the connector and examine both the sensor pins and harness terminals. Clean with electrical contact cleaner and check for physical damage. On used excavators, pay special attention to harness routing—look for wire insulation wear at points where the harness contacts the engine or frame.

Step 2: Electrical Testing with Multimeter

With the connector disconnected and ignition off, use a digital multimeter (DMM) to measure resistance across the ECT sensor terminals. At room temperature (20°C/68°F), resistance should typically read between 2,000-3,000 ohms (consult your service manual for exact specifications). If the reading shows infinite resistance (OL), the sensor has failed internally. Next, check for continuity in the wiring harness from the sensor connector back to the ECM connector—any break indicates damaged wiring requiring repair or replacement.

Step 3: Voltage Signal Testing

Reconnect the sensor and turn the ignition to the ON position (engine off). Back-probe the sensor signal wire at the connector using your multimeter set to DC voltage. You should see approximately 0.5-3.5V depending on current coolant temperature. A reading of 5V or battery voltage confirms an open circuit condition. For used machines, remove the sensor and inspect the mounting boss threads for coolant leaks that may have damaged the sensor or wiring over time.

Step 4: Component Replacement and Verification

If testing confirms a faulty ECT sensor, replace it with a genuine Sumitomo or OEM-equivalent part. Apply thread sealant (not Teflon tape) to prevent coolant leaks. If wiring damage is found, repair using heat-shrink solder connections and reroute away from heat sources. After repairs, clear the fault code using diagnostic software or by disconnecting the battery for 5 minutes. Test-run the machine and monitor for code recurrence.

---

Disclaimer: This guide provides general troubleshooting information for educational purposes. Always consult the official Sumitomo service manual for your specific machine serial number and seek assistance from qualified heavy equipment technicians for complex electrical diagnostics or repairs. Improper repairs may void warranties or create safety hazards.