Sumitomo SH220LC-6 Fault Code 606: Complete Diagnostic Guide

What is Sumitomo SH220LC-6 Fault Code 606?

Fault Code 606 on the Sumitomo SH220LC-6 excavator indicates a malfunction in the Engine Speed Sensor circuit or an abnormal signal from the engine RPM detection system. This code is triggered when the Electronic Control Module (ECM) detects irregular voltage patterns, signal interruptions, or complete loss of communication from the engine speed sensor.

The engine speed sensor is critical for this machine's performance because it provides real-time RPM data to the ECM, which controls fuel injection timing, hydraulic pump output, and engine protection systems. Without accurate speed readings, the ECM cannot optimize performance or prevent over-revving damage. On used SH220LC-6 models, this sensor circuit is particularly vulnerable to degradation from years of vibration, heat exposure, and connector corrosion common in high-hour machines.

Common Symptoms

When Code 606 is active, operators typically experience:

• Erratic engine RPM or inability to maintain consistent idle speed
• Illuminated warning lights on the instrument panel, specifically engine-related indicators
• Reduced hydraulic power or sluggish boom/arm response due to ECM entering protective derate mode
• Engine stalling during low-idle conditions or when engaging hydraulics under load
• Difficulty starting or extended cranking periods as the ECM struggles to detect engine rotation

Potential Causes

The most common technical reasons for Code 606 on used SH220LC-6 excavators include:

• Faulty engine speed sensor (magnetic pickup type) due to internal coil failure or physical damage from debris impact
• Damaged wiring harness between the sensor and ECM, especially at known rub points near the engine mounting brackets
• Corroded or loose electrical connectors at the sensor plug or ECM interface—extremely common on machines with 5,000+ hours
• Worn flywheel ring gear causing irregular magnetic field disruption and inconsistent signal generation
• ECM internal fault or corrupted software, though less common than sensor-level issues
• Excessive air gap between the sensor tip and flywheel teeth due to mounting bracket wear or improper installation

How to Troubleshoot and Fix Code 606

Step 1: Visual Inspection Begin by locating the engine speed sensor mounted on the flywheel housing. Inspect the wiring harness for obvious damage, abrasion points where it contacts the frame, or melted insulation from exhaust heat. Check the connector for corrosion, bent pins, or moisture intrusion—clean with electrical contact cleaner if necessary.

Step 2: Sensor Resistance Testing Disconnect the sensor connector and use a digital multimeter to measure resistance across the sensor terminals. Specifications typically range between 150-300 ohms (consult your service manual). Readings outside this range indicate sensor failure requiring replacement.

Step 3: Signal Voltage Check Reconnect the sensor and backprobe the connector with your multimeter set to AC voltage. Manually rotate the engine with the starter while monitoring voltage output—you should see 0.5-3.0 VAC pulses. No signal indicates a dead sensor; erratic signals suggest wiring issues or flywheel damage.

Step 4: Inspect Air Gap and Flywheel Measure the air gap between the sensor tip and flywheel teeth using feeler gauges (specification typically 0.5-1.5mm). On used excavators, check for broken flywheel teeth, metal debris buildup on the sensor tip, or elongated mounting holes causing improper sensor positioning.

Step 5: Harness Continuity Test Trace the harness from sensor to ECM, checking for continuity and short circuits to ground. Pay special attention to areas where the harness passes through bulkheads or near moving components—common failure points on high-hour machines.

Step 6: Clear Code and Test After repairs, clear the fault code using Sumitomo diagnostic software or by disconnecting the battery for 10 minutes. Operate the machine through various RPM ranges and load conditions to verify the fix.

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Disclaimer: This guide provides general diagnostic procedures for Code 606. Always consult the official Sumitomo service manual for your specific serial number and consider professional assistance for complex electrical diagnostics or ECM-level repairs.