Sumitomo SH240-5 Fault Code 606: Complete Diagnostic Guide

What is Sumitomo SH240-5 Fault Code 606?

Fault Code 606 on the Sumitomo SH240-5 excavator indicates a malfunction in the pump solenoid control circuit, specifically related to abnormal current or voltage detection in the hydraulic pump proportional control system. This code is generated when the Electronic Control Unit (ECU) detects an electrical irregularity in the pump solenoid valve circuit that regulates hydraulic flow and pressure.

This fault is critical for the SH240-5 because it directly affects the machine's hydraulic performance. The proportional solenoid valve controls pump displacement, which determines how much hydraulic power is available for all machine functions. When this circuit malfunctions, the excavator may experience reduced performance or enter a protective derate mode to prevent damage to the hydraulic system.

Common Symptoms

When Code 606 is active on your SH240-5, operators typically experience:

• Reduced hydraulic power across all functions (boom, arm, bucket, and swing movements become sluggish)
• Warning light illumination on the instrument panel, often accompanied by an audible alarm
• Erratic pump response where hydraulic functions surge or hesitate unpredictably
• Engine derating where the ECU limits engine RPM to protect the hydraulic system
• Complete loss of certain hydraulic functions in severe cases, particularly under load

Potential Causes

Code 606 typically stems from these technical issues, especially common in used excavators:

• Damaged pump solenoid coil due to overheating, internal short circuits, or coil winding breakdown
• Wiring harness damage at known rub points near the main pump mounting area or along the chassis frame
• Corroded or loose electrical connectors at the solenoid valve or ECU connections, particularly from water intrusion
• Failed pump solenoid driver circuit within the main ECU due to voltage spikes or age-related component failure
• Incorrect solenoid resistance caused by internal contamination or mechanical wear in high-hour machines
• Ground fault issues in the chassis grounding system affecting solenoid control signals

How to Troubleshoot and Fix Code 606

Step 1: Initial Inspection and Code Verification

Connect a diagnostic scanner compatible with Sumitomo systems to verify Code 606 is current (not historical). Clear the code and attempt to reproduce the fault during normal operation. Document whether the code returns immediately or under specific conditions. For used excavators, check the maintenance history for previous electrical repairs or pump work.

Step 2: Solenoid Electrical Testing

Disconnect the pump solenoid connector and measure resistance across the solenoid coil terminals using a digital multimeter. Typical resistance should read between 10-30 ohms (consult your service manual for exact specifications). Also check for continuity between each solenoid terminal and ground—there should be infinite resistance (open circuit). Any reading below 10K ohms indicates a ground fault.

Step 3: Harness and Connector Inspection

Thoroughly inspect the wiring harness from the ECU to the pump solenoid, paying special attention to areas where the harness routes near sharp edges or moving components. On used SH240-5 machines, check behind the pump mounting area where vibration commonly causes wire chafing. Clean all connector pins with electrical contact cleaner and inspect for corrosion, bent pins, or moisture. Apply dielectric grease before reconnection.

Step 4: Voltage Supply Testing

With the ignition on but engine off, backprobe the solenoid connector to verify supply voltage (typically 12-24V depending on system design). If voltage is present but the solenoid tests good, the issue likely resides in the ECU driver circuit. If no voltage is detected, trace back toward the ECU checking for blown fuses, broken wires, or faulty relays.

Step 5: Component Replacement and Verification

If testing identifies a faulty solenoid, replace it with a genuine Sumitomo part or verified OEM equivalent. After replacement, clear all fault codes, cycle the ignition, and perform a complete operational test under load. Monitor for code recurrence over several operating hours.

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Disclaimer: This guide provides general diagnostic information for Code 606 on Sumitomo SH240-5 excavators. Hydraulic and electrical systems can be dangerous. Always consult your machine's service manual and consider professional assistance from certified Sumitomo technicians for complex repairs, especially on used equipment where multiple underlying issues may exist.