Sumitomo SH290-5 Fault Code 606: Complete Diagnostic Guide

What is Sumitomo SH290-5 Fault Code 606?

Fault Code 606 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 ECM (Engine Control Module). This code specifically signals that the coolant temperature sensor is either sending values outside the normal operating range, experiencing a circuit fault, or has completely failed to communicate with the controller.

This fault is critical for the SH290-5's performance because the ECM relies on accurate coolant temperature data to control fuel injection timing, engine protection protocols, and hydraulic oil temperature management. When this sensor fails, the machine may enter a derate mode to prevent potential engine damage from overheating or improper combustion cycles.

Common Symptoms

When Code 606 is active on your Sumitomo SH290-5, operators typically experience:

• Engine warning light illuminated on the instrument panel (often amber or red depending on severity)
• Reduced engine power or automatic derate mode, limiting RPM and hydraulic flow
• Erratic temperature gauge readings showing abnormally high, low, or fluctuating coolant temperatures
• Extended warm-up periods or failure to reach normal operating temperature
• Rough idle or poor throttle response due to incorrect fuel mapping based on faulty temperature data

Potential Causes

The most common technical causes for Code 606 on used SH290-5 excavators include:

• Coolant temperature sensor failure due to age, corrosion, or internal element degradation
• Damaged wiring harness at common rub points near the engine block or frame rails
• Corroded or loose connector pins at the sensor plug, especially on machines with high hours
• ECM internal fault affecting the temperature sensor circuit (less common)
• Coolant contamination causing sensor fouling or physical damage to the sensor probe
• Broken or shorted sensor ground wire creating intermittent circuit faults

How to Troubleshoot and Fix Code 606

Step 1: Visual Inspection Locate the coolant temperature sensor (typically mounted on the engine block near the thermostat housing). Inspect the wiring harness for visible damage, chafing, or corrosion. On used excavators, check for oil or coolant leaks that may have compromised the connector. Clean all connector pins with electrical contact cleaner and ensure tight connections.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor 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). Test the harness continuity from the sensor connector back to the ECM—resistance should be less than 5 ohms. Check for short circuits to ground (should read infinite resistance).

Step 3: Live Data Analysis Connect Sumitomo diagnostic software or a compatible scan tool to monitor live coolant temperature data. Compare the sensor reading with actual engine temperature using an infrared thermometer. If the variance exceeds 10°F (5°C), replace the sensor. For used machines, always inspect the sensor mounting boss for thread damage or coolant leaks before installing the new component.

Step 4: Component Replacement If testing confirms sensor failure, replace with an OEM or equivalent quality sensor (aftermarket sensors on used equipment often cause repeat failures). Apply thread sealant appropriate for coolant systems and torque to manufacturer specifications (typically 15-20 ft-lbs). Clear the fault code and perform a cold start test to verify proper operation.

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Disclaimer: This guide provides general troubleshooting information. Always consult your Sumitomo SH290-5 service manual and consider professional diagnostic services for complex electrical issues or if you're unfamiliar with excavator systems.