Sumitomo SH210LC-5LR Fault Code 487: Complete Diagnostic Guide

What is Sumitomo SH210LC-5LR Fault Code 487?

Fault Code 487 on the Sumitomo SH210LC-5LR indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading detected by the engine control module (ECM). This diagnostic trouble code (DTC) is triggered when the ECM receives voltage signals outside the normal operating range from the coolant temperature sensor, typically between 0.5-4.5 volts.

This code is critical for the SH210LC-5LR because the engine relies on accurate coolant temperature data to manage fuel injection timing, idle speed control, and protective derate modes. The Mitsubishi 6D24-TLE engine powering this excavator uses coolant temperature readings to prevent overheating damage and optimize combustion efficiency. Ignoring this fault can lead to engine damage, reduced performance, or unexpected shutdowns.

Common Symptoms

When Code 487 is active on your Sumitomo excavator, you may experience:

• Engine warning light illuminated on the instrument panel (typically yellow or amber)
• Erratic temperature gauge readings or gauge stuck at cold/hot positions
• Hard starting when the engine is cold due to improper fuel enrichment
• Poor engine performance including rough idle or reduced power output
• Cooling fan running continuously regardless of actual engine temperature
• Engine derate mode activating prematurely, limiting hydraulic functions

Potential Causes

The most common technical causes for Code 487 on used SH210LC-5LR excavators include:

• Failed coolant temperature sensor (NTC thermistor degradation common after 5,000+ hours)
• Damaged wiring harness between the sensor and ECM, particularly at flex points near the engine mount
• Corroded or loose connector pins at the sensor or ECM harness connection
• Shorted or open circuit in the sensor signal wire (common rub-through point behind the injection pump)
• ECM internal fault (less common, but possible in high-hour machines)
• Low coolant level causing sensor exposure and false readings
• Contaminated coolant creating electrical resistance changes at the sensor element

How to Troubleshoot and Fix Code 487

Step 1: Visual Inspection Begin by checking the coolant level in the radiator and overflow tank. Inspect the coolant temperature sensor (located on the thermostat housing) for physical damage, coolant leaks, or corrosion on the electrical connector. On used excavators, carefully examine the entire wiring harness from sensor to ECM for chafing, especially where it passes near moving components or sharp edges.

Step 2: Electrical Testing Disconnect the coolant temperature sensor connector and measure resistance across the sensor terminals using a digital multimeter. At 68°F (20°C), resistance should read approximately 2,000-3,000 ohms. Warm the engine and recheck—resistance should decrease as temperature rises. If readings are infinite (open circuit) or zero (short circuit), replace the sensor.

Step 3: Circuit Verification With the sensor disconnected, check for 5-volt reference voltage at the harness connector from the ECM. Measure continuity between the sensor ground wire and chassis ground (should be less than 1 ohm). Inspect for voltage on the signal wire with the key on, engine off—any reading above 0.2V indicates a short to power.

Step 4: Advanced Diagnostics Use Sumitomo diagnostic software or a compatible scan tool to monitor live coolant temperature data while warming the engine. Compare ECM readings to an infrared thermometer measurement at the thermostat housing. A variance greater than 15°F indicates sensor or circuit problems. For used machines with over 8,000 hours, inspect ECM connector terminals for corrosion or bent pins before condemning the module.

Disclaimer: This guide provides general diagnostic information. Always consult the official Sumitomo service manual for your specific machine serial number and consider professional diagnostic services for complex electrical issues. Improper repairs may cause additional damage or safety hazards.