Sumitomo SH210-5 Fault Code 108: Complete Diagnostic Guide

What is Sumitomo SH210-5 Fault Code 108?

Fault Code 108 on the Sumitomo SH210-5 excavator indicates an Engine Coolant Temperature (ECT) Sensor Circuit malfunction. This code triggers when the Engine Control Module (ECM) detects an abnormal voltage signal from the coolant temperature sensor, typically indicating an open circuit, short circuit, or sensor failure.

The ECT sensor plays a critical role in monitoring engine operating temperature and provides essential data for fuel injection timing, engine warm-up cycles, and overheating protection. On used SH210-5 models, this sensor is particularly vulnerable to connector corrosion and wiring degradation due to its location near heat sources and exposure to coolant leaks.

Common Symptoms

When Code 108 is active, operators typically experience:

• Check Engine Light or warning lamp illuminated on the instrument panel
• Hard starting or rough idle, especially during cold starts
• Excessive black smoke from exhaust due to improper fuel mixture calculations
• Engine running in failsafe mode with reduced power output or limited RPM range
• Inaccurate temperature gauge readings showing erratic or frozen temperature displays

Potential Causes

The most common technical reasons for Code 108 on used SH210-5 excavators include:

• Failed ECT sensor due to internal element degradation (common after 5,000+ operating hours)
• Damaged wiring harness caused by rubbing against engine components or heat shield deterioration
• Corroded electrical connectors at the sensor or ECM connection points from coolant exposure
• Open or short circuit in the sensor signal wire between the sensor and ECM
• Poor ground connection at the sensor mounting point or ECM ground strap
• ECM internal fault (rare, but possible on high-hour machines with previous electrical issues)

How to Troubleshoot and Fix Code 108

Step 1: Visual Inspection Begin by inspecting the ECT sensor located on the engine block near the thermostat housing. Check for coolant leaks, corroded terminals, or damaged wiring. On used excavators, pay special attention to harness routing where wires contact hot engine surfaces or sharp metal edges.

Step 2: Electrical Testing Disconnect the ECT sensor connector and use a digital multimeter to measure resistance across the sensor terminals. At 68°F (20°C), resistance should read approximately 2,000-3,000 ohms (consult service manual for exact specifications). Test the wiring harness for continuity between the sensor connector and ECM pins and check for shorts to ground.

Step 3: Signal Voltage Check With the ignition on and sensor disconnected, measure reference voltage at the harness connector—should read approximately 5 volts. If voltage is absent, trace the circuit back to the ECM for breaks or damaged wires.

Step 4: Component Replacement If the sensor tests out of specification or wiring shows damage, replace the faulty component. For used machines, always apply dielectric grease to connectors and secure harnesses away from heat sources to prevent recurrence.

Step 5: Clear Code and Verify After repairs, clear the fault code using diagnostic software or by disconnecting the battery for 30 seconds. Run the engine through a complete warm-up cycle and verify the code does not return.

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Disclaimer: This guide provides general troubleshooting information. Always consult the Sumitomo SH210-5 service manual for exact specifications and procedures. If you're uncomfortable performing electrical diagnostics, contact a certified heavy equipment technician to prevent further damage to electrical systems.