Sumitomo SH210-5 Fault Code 118: Complete Diagnostic Guide

What is Sumitomo SH210-5 Fault Code 118?

Fault Code 118 on the Sumitomo SH210-5 excavator indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal engine coolant temperature reading. This code is triggered when the Electronic Control Module (ECM) detects voltage readings outside the expected range from the coolant temperature sensor, typically indicating either an open circuit, short circuit, or sensor failure.

The coolant temperature sensor is critical for the SH210-5's performance because it directly affects fuel injection timing, engine warm-up cycles, and thermal protection systems. When this sensor provides incorrect data, the ECM cannot properly manage engine operations, potentially leading to reduced efficiency, increased emissions, or engine protection mode activation.

Common Symptoms

When Code 118 is active on your Sumitomo SH210-5, operators typically experience:

• Engine warning light illuminated on the instrument panel or diagnostic display
• Hard starting conditions, especially during cold weather, due to improper fuel enrichment
• Rough idle or erratic engine performance during warm-up phase
• Engine derate mode activation, limiting power output to protect the engine
• Abnormal temperature gauge readings showing extremely high or low coolant temperatures that don't match actual engine conditions

Potential Causes

The most common technical reasons for Code 118 on used SH210-5 excavators include:

• Failed coolant temperature sensor due to internal element degradation (common after 5,000+ operating hours)
• Corroded or damaged wiring harness connectors at the sensor plug, especially where the harness routes near the engine block
• Broken or chafed wiring along known rub points near the engine mount brackets and valve cover
• Poor ground connection at the sensor or ECM ground points
• Contaminated coolant causing sensor element coating or failure
• ECM internal fault (rare, but possible in high-hour machines)

How to Troubleshoot and Fix Code 118

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, bent pins, or moisture intrusion. Check the wiring harness from the sensor to the ECM for chafing, particularly where it contacts metal brackets or passes through grommets—a common failure point on used excavators.

Step 2: Electrical Testing Disconnect the sensor and use a digital multimeter to measure resistance across the sensor terminals. A functional sensor typically shows 2,000-3,000 ohms at room temperature (refer to Sumitomo specifications). Also check for continuity in the wiring harness between the sensor connector and ECM pins. Measure voltage supply from the ECM (should be approximately 5 volts reference voltage).

Step 3: Component Replacement and Verification If the sensor tests outside specifications or wiring shows high resistance, replace the faulty component. For used machines, always apply dielectric grease to connectors during reassembly to prevent future corrosion. Clear the fault code using Sumitomo diagnostic software or a compatible scanner, then monitor during a complete warm-up cycle to verify the repair.

Disclaimer: This guide provides general diagnostic procedures. Always consult the official Sumitomo service manual for your specific serial number and consider professional diagnosis for complex electrical issues or if you lack proper diagnostic equipment.