Sumitomo SH220LC-6 Fault Code 202: Complete Diagnostic Guide

What is Sumitomo SH220LC-6 Fault Code 202?

Fault Code 202 on the Sumitomo SH220LC-6 excavator indicates a malfunction in the Engine Coolant Temperature (ECT) sensor circuit or an abnormal coolant temperature reading being sent to the Engine Control Module (ECM).

This diagnostic trouble code specifically monitors the coolant temperature sensor circuit, which provides critical data to the ECM for proper fuel injection timing, engine protection, and operational efficiency. The SH220LC-6 uses this sensor to prevent engine overheating and maintain optimal performance in the Isuzu diesel engine. When this code activates, the ECM may default to a preset temperature value, potentially causing improper fuel mixture, reduced power output, or engine protection mode activation. For used excavators operating in demanding conditions, this sensor's accuracy is essential for preventing catastrophic engine damage.

Common Symptoms

When Code 202 is active on your SH220LC-6, you may experience:

• Engine warning light illuminated on the instrument cluster, often accompanied by a temperature warning indicator
• Reduced engine power or derate mode, limiting maximum RPM and hydraulic performance
• Erratic temperature gauge readings that fluctuate abnormally or remain stuck at cold/hot positions
• Hard starting conditions, especially when the engine is cold, due to improper fuel enrichment
• Black smoke from exhaust caused by incorrect fuel-to-air ratios based on faulty temperature data

Potential Causes

The most common technical reasons for Code 202 on used SH220LC-6 excavators include:

• Faulty coolant temperature sensor (most common on machines with 5,000+ hours)
• Damaged or corroded wiring harness at connector points, particularly where the harness routes near the engine block or exhaust manifold
• Broken or frayed sensor wires due to vibration and heat cycling over years of operation
• Poor electrical ground connection at the ECM or sensor mounting point
• Contaminated coolant causing sensor element degradation or physical damage to the sensor tip
• ECM internal fault (rare, but possible in older machines with electrical system issues)

How to Troubleshoot and Fix Code 202

Step 1: Visual Inspection Begin by locating the ECT sensor on the engine block (typically near the thermostat housing on Isuzu engines). Inspect the sensor connector for corrosion, oil contamination, or moisture intrusion. On used excavators, check for wiring harness abrasion where cables contact metal surfaces or pass near hot exhaust components.

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 2,000-3,000 ohms (consult service manual for exact specifications). Test the harness continuity from sensor connector to ECM pins, checking for open circuits or short-to-ground conditions.

Step 3: Live Data Analysis Connect Sumitomo diagnostic software or a compatible scan tool to monitor live coolant temperature data. Compare the displayed temperature with an infrared thermometer reading on the engine block. A variance greater than 10°F indicates sensor failure.

Step 4: Voltage Supply Check With ignition on and sensor disconnected, measure reference voltage at the harness connector (should be approximately 5 volts). Low voltage indicates ECM or harness issues rather than sensor failure.

Step 5: Repair and Verification Replace the coolant temperature sensor if resistance or voltage tests fail specifications. For used machines, always apply dielectric grease to connector terminals before reassembly to prevent future corrosion. Clear the fault code and perform a cold-to-hot engine cycle to verify proper sensor operation across the temperature range.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Sumitomo service manual and consider professional technician assistance for complex electrical diagnostics or if you're uncomfortable performing these procedures.