Sumitomo SH210-6 Fault Code 118: Complete Diagnostic Guide

What is Sumitomo SH210-6 Fault Code 118?

Fault Code 118 on the Sumitomo SH210-6 excavator indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal temperature reading beyond the normal operating range. This code is triggered when the Electronic Control Module (ECM) detects either an open circuit, short circuit, or implausible voltage signal from the coolant temperature sensor.

The coolant temperature sensor plays a critical role in engine management for the SH210-6. It directly influences fuel injection timing, idle speed control, and engine warm-up cycles. When this sensor fails or sends incorrect data, the ECM cannot properly regulate engine temperature, potentially leading to overheating, poor fuel economy, or engine damage on older used machines.

Common Symptoms

When Code 118 is active on your Sumitomo SH210-6, you may experience:

• Check Engine Light or warning lamp illuminated on the instrument panel
• Hard starting or extended cranking times, especially during cold starts
• Rough idle or erratic engine RPM fluctuations during warm-up
• Black smoke from exhaust due to improper fuel mixture calculations
• Engine running cooler or hotter than normal operating temperature (185-205°F)
• Cooling fan running continuously regardless of actual engine temperature

Potential Causes

The most common technical causes for Code 118 on used SH210-6 excavators include:

• Faulty coolant temperature sensor – internal resistance degradation common after 5,000+ operating hours
• Damaged wiring harness – particular wear point near the engine block where harness rubs against mounting brackets
• Corroded or loose connector pins at the sensor plug (2-pin connector)
• Shorted sensor wiring to ground or power, often from insulation breakdown
• Low coolant level causing sensor exposure to air instead of coolant
• ECM internal failure (rare, but possible on high-hour machines)
• Aftermarket sensor incompatibility if previously replaced with non-OEM parts

How to Troubleshoot and Fix Code 118

Step 1: Visual Inspection Begin with a thorough visual examination of the coolant temperature sensor located on the engine block near the thermostat housing. Check coolant level first—low coolant can cause false readings. Inspect the sensor connector for corrosion, bent pins, or moisture intrusion. On used excavators, carefully trace the wiring harness from sensor to ECM, looking for chafing, cuts, or evidence of previous repairs with electrical tape.

Step 2: Electrical Testing Disconnect the sensor and use a digital multimeter to check resistance. At 68°F (20°C), resistance should typically read 2,000-3,000 ohms; at 176°F (80°C), approximately 300-400 ohms (consult service manual for exact specifications). Test harness continuity from the ECM connector to the sensor plug—you should read less than 5 ohms resistance. Check for shorts to ground (should read infinite resistance with sensor disconnected).

Step 3: Sensor Replacement and Verification If resistance values are out of specification or erratic, replace the coolant temperature sensor with an OEM Sumitomo part. Apply dielectric grease to connector pins before reassembly to prevent future corrosion. Clear codes using diagnostic software (Sumitomo-compatible scan tool or generic OBD reader), then operate the machine through a complete warm-up cycle to verify the repair.

Disclaimer: This guide provides general diagnostic information. Always consult the official Sumitomo service manual for your specific machine serial number. If you're uncomfortable performing electrical diagnostics, contact a certified heavy equipment technician to prevent further damage to your excavator's systems.