Sumitomo SH220LC-6 Fault Code 602: Complete Diagnostic Guide

What is Sumitomo SH220LC-6 Fault Code 602?

Fault Code 602 on the Sumitomo SH220LC-6 excavator indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading detected by the Electronic Control Module (ECM). This code specifically signals that the ECM has detected either an out-of-range voltage signal, an open circuit, or a short circuit in the coolant temperature sensor system.

The coolant temperature sensor is critical for the SH220LC-6's engine management system. It provides real-time data that the ECM uses to adjust fuel injection timing, regulate idle speed, and activate cooling fan operation. When this sensor fails or sends erratic signals, the engine cannot optimize performance, potentially leading to overheating, poor fuel economy, or reduced hydraulic efficiency.

Common Symptoms

When Code 602 is active on your Sumitomo SH220LC-6, operators typically experience:

• Warning light illumination on the instrument panel, often accompanied by an audible alarm
• Engine running in derate mode or limp mode, limiting RPM and hydraulic power output
• Difficulty starting, especially in cold conditions, or extended cranking times
• Cooling fan running continuously at high speed, regardless of actual engine temperature
• Erratic temperature gauge readings or gauge stuck at minimum/maximum position

Potential Causes

The most common technical reasons for Code 602 on used SH220LC-6 excavators include:

• Coolant temperature sensor failure due to age-related degradation or internal resistance drift
• Wiring harness damage at known rub points near the engine block or cylinder head, particularly where the harness contacts moving components
• Corroded or loose electrical connectors at the sensor plug, common in machines with coolant leaks or extended outdoor storage
• ECM internal fault or corrupted calibration data (less common but possible in high-hour machines)
• Damaged sensor threads causing poor thermal contact with the coolant jacket

How to Troubleshoot and Fix Code 602

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor location (typically on the cylinder head or thermostat housing). Check for obvious damage, coolant leaks around the sensor, or corroded connector pins. On used excavators, examine the wiring harness for wear points where it may contact the engine block.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance. At room temperature (68°F/20°C), resistance should typically read 2,000-3,000 ohms; consult your service manual for exact specifications. Check connector voltage with the ignition on—you should see approximately 5 volts reference voltage from the ECM.

Step 3: Circuit Verification Test for continuity between the sensor connector and ECM pins to identify open circuits. Check for shorts to ground using the multimeter's continuity function. Pay special attention to harness sections near exhaust manifolds where heat damage is common.

Step 4: Component Replacement If the sensor tests outside specifications or wiring shows damage, replace the faulty component. For used machines, always apply dielectric grease to connector pins and verify proper torque specifications when installing a new sensor to ensure accurate thermal readings.

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Disclaimer: This guide provides general diagnostic information. Always consult the Sumitomo SH220LC-6 service manual for exact specifications and safety procedures. If you're uncomfortable performing electrical diagnostics, consult a certified heavy equipment technician to prevent further damage to the machine's electrical system.