Sumitomo SH220LC-6 Fault Code 340: Complete Diagnostic Guide

What is Sumitomo SH220LC-6 Fault Code 340?

Fault Code 340 on the Sumitomo SH220LC-6 excavator indicates a malfunction in the hydraulic pump control system, specifically related to the pump displacement sensor or its associated circuit. This code triggers when the Electronic Control Module (ECM) detects an abnormal signal from the pump's angle sensor, which monitors the swash plate position and regulates hydraulic flow output.

This fault is critical because the pump displacement sensor directly controls the excavator's hydraulic power delivery. When this system fails, the ECM cannot properly adjust pump output to match operational demands, resulting in reduced performance and potential damage to hydraulic components. In the SH220LC-6's sophisticated hydraulic management system, accurate sensor feedback is essential for maintaining optimal fuel efficiency and preventing over-pressurization.

Common Symptoms

When Code 340 is active, operators typically experience:

• Reduced hydraulic power across all functions, with noticeably sluggish boom, arm, and bucket movements
• Erratic hydraulic response where implements move inconsistently or surge unexpectedly during operation
• Warning lamp illumination on the instrument cluster, often accompanied by an audible alarm
• Engine RPM fluctuations under load as the ECM attempts to compensate for incorrect pump feedback
• Increased fuel consumption due to inefficient pump control and compensation strategies

Potential Causes

The most common technical causes for Code 340 in used SH220LC-6 excavators include:

• Pump displacement sensor failure due to internal wear, contamination, or electrical component degradation
• Wiring harness damage at known rub points near the hydraulic pump mounting area where vibration causes insulation breakdown
• Connector corrosion at the sensor plug, especially in machines operating in wet or marine environments
• ECM voltage supply issues providing incorrect reference voltage to the sensor circuit
• Mechanical binding of the swash plate mechanism preventing proper sensor operation
• Contaminated hydraulic oil causing sensor fouling or erratic readings

How to Troubleshoot and Fix Code 340

Step 1: Visual Inspection Begin by thoroughly inspecting the pump displacement sensor and its wiring harness. On used excavators, check for harness chafing against the pump housing, frame rails, or hydraulic lines. Examine all connectors for corrosion, bent pins, or hydraulic oil contamination. Clean connectors with electrical contact cleaner and ensure proper seating.

Step 2: Electrical Testing Using a digital multimeter, measure the sensor's supply voltage with the key in the "ON" position (should read approximately 5 volts). Check sensor output voltage while manually moving the pump control (if accessible)—readings should change smoothly between 0.5-4.5 volts. Test harness continuity from sensor to ECM and verify ground circuit resistance is below 5 ohms.

Step 3: Sensor Replacement and Calibration If electrical tests indicate sensor failure, replace the pump displacement sensor with a genuine Sumitomo part. After installation, use Sumitomo diagnostic software to perform sensor calibration and clear stored codes. For used machines, always replace the O-ring seals and check hydraulic oil condition—contaminated oil often indicates the root cause requiring a full hydraulic system flush.

Step 4: Verification Testing After repairs, operate the excavator through all hydraulic functions under varying loads. Monitor live data using diagnostic software to confirm sensor readings match pump commands throughout the operating range.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Sumitomo service manual for your specific machine serial number and seek professional assistance for complex hydraulic system repairs. Improper diagnostics can lead to costly component damage or safety hazards.