Sumitomo SH380LHD-6 Fault Code 1655: Complete Diagnostic Guide

What is Sumitomo SH380LHD-6 Fault Code 1655?

Fault Code 1655 indicates a malfunction in the hydraulic pump control system, specifically related to the pump displacement sensor circuit or its associated control voltage.

This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormal signal from the pump displacement feedback sensor. On the SH380LHD-6, this sensor monitors the swash plate angle of the main hydraulic pump, which directly controls hydraulic flow and pressure. This code is critical because it affects the excavator's ability to properly regulate hydraulic power, potentially leading to reduced performance, erratic boom/arm movements, or complete hydraulic system shutdown to prevent damage.

Common Symptoms

When Code 1655 is active on your Sumitomo SH380LHD-6, operators typically experience:

• Illuminated warning lamp on the instrument cluster with possible error message display
• Reduced hydraulic power or sluggish response during digging, lifting, or swing operations
• Erratic hydraulic function where boom/arm speed varies unpredictably under load
• Engine derate mode activation, limiting RPM to protect the hydraulic system
• Intermittent loss of hydraulic pressure particularly during high-demand operations

Potential Causes

The most common technical reasons for Code 1655 appearing on used SH380LHD-6 excavators include:

• Damaged or corroded wiring harness at the pump displacement sensor connector (common wear point due to vibration and heat exposure)
• Failed pump displacement sensor caused by internal component degradation or contaminated hydraulic fluid entering the sensor housing
• Poor electrical ground connection at the sensor mounting point or ECM ground terminals
• ECM voltage supply issue providing incorrect reference voltage (typically should be 5V ±0.5V)
• Hydraulic pump mechanical wear preventing proper swash plate positioning, causing sensor signal drift
• Connector pin corrosion from water infiltration in the engine compartment or pump area

How to Troubleshoot and Fix Code 1655

Step 1: Visual Inspection Begin by inspecting the pump displacement sensor located on the main hydraulic pump body. Check the wiring harness for abrasion, cuts, or heat damage along its entire length, paying special attention to areas where the harness contacts metal surfaces or passes near hot components. On used excavators, examine connector pins for corrosion, bent terminals, or hydraulic fluid contamination.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure the reference voltage from the ECM—it should read approximately 5 volts DC. Check sensor resistance across the signal pins (typical range: 1-5 kΩ, consult service manual for exact specs). Verify ground continuity between the sensor ground pin and chassis ground (should be less than 1 ohm).

Step 3: Sensor Signal Testing With the ignition on and sensor connected, use Sumitomo diagnostic software or a compatible scan tool to monitor live sensor voltage while manually moving the pump swash plate (engine off, hydraulic pressure relieved). The voltage should change smoothly between approximately 0.5V to 4.5V. Erratic readings or frozen values indicate sensor failure.

Step 4: Component Replacement and Verification If electrical tests confirm sensor failure, replace the pump displacement sensor using OEM or equivalent quality parts. For used machines, always replace the connector pigtail if any corrosion is present. After replacement, clear the fault code, operate the machine through all hydraulic functions, and verify the code does not return.

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Disclaimer: This guide provides general troubleshooting information for Code 1655. Always consult the official Sumitomo service manual for your specific serial number and follow proper lockout/tagout procedures. If unfamiliar with hydraulic systems or electrical diagnostics, contact a certified Sumitomo technician to prevent injury or equipment damage.