Sumitomo SH240-6 Fault Code 1655: Complete Diagnostic Guide

What is Sumitomo SH240-6 Fault Code 1655?

Fault Code 1655 on the Sumitomo SH240-6 excavator indicates a hydraulic pump solenoid circuit malfunction, specifically related to the main pump flow control system. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects an abnormal voltage or current signal from the proportional solenoid valve that regulates hydraulic pump displacement.

This code directly affects the excavator's ability to match engine power with hydraulic demand. The proportional solenoid modulates pump output based on operator input and load conditions. When this circuit fails, the machine cannot optimize fuel efficiency or deliver precise hydraulic control, which is critical for the SH240-6's load-sensing hydraulic system.

Common Symptoms

When Code 1655 is active, operators typically experience:

• Loss of hydraulic power or noticeably sluggish boom, arm, and bucket movements
• Increased engine RPM without corresponding hydraulic response (pump not matching engine output)
• Intermittent or constant warning light on the instrument cluster
• Rough or jerky hydraulic operation, particularly during combined functions
• Reduced fuel efficiency as the system defaults to a fixed pump displacement mode

Potential Causes

The most common technical failures triggering Code 1655 on used SH240-6 excavators include:

• Damaged or corroded wiring harness at the pump solenoid connector (common wear point near the pump mounting area)
• Failed proportional solenoid valve due to internal coil breakdown or mechanical sticking from contaminated hydraulic fluid
• Broken or frayed wires where the harness routes over the engine block (heat and vibration damage)
• Poor ground connection at the ECM or solenoid mounting points
• ECM internal fault (less common, but possible in high-hour machines)
• Hydraulic fluid contamination causing solenoid valve spool seizure

How to Troubleshoot and Fix Code 1655

Step 1: Visual Inspection Begin by inspecting the main pump solenoid connector located on the hydraulic pump assembly. Look for corrosion, oil contamination, or bent pins. On used excavators, check for harness chafing where it passes near the engine mount and turbocharger—this is a known wear point on the SH240-6.

Step 2: Electrical Testing Using a digital multimeter, check solenoid coil resistance. Disconnect the solenoid connector and measure across the terminals. Typical resistance should be 15-25 ohms (consult service manual for exact specs). Also verify supply voltage at the connector with ignition on—should read approximately 12-14 volts.

Step 3: Circuit Continuity Check Test wiring continuity between the ECM connector and solenoid. Check for shorts to ground or open circuits. Pay special attention to wire integrity near moving components and heat sources.

Step 4: Solenoid Replacement or Repair If electrical values are out of specification, replace the proportional solenoid valve. Before installation, flush the hydraulic system and replace filters—contamination often causes premature solenoid failure in used machines.

Step 5: Clear Code and Test After repairs, use Sumitomo diagnostic software (or compatible scan tool) to clear the fault code. Perform a full operational test under load to verify proper pump response.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Sumitomo service manual for your specific serial number. Complex hydraulic and electrical repairs should be performed by qualified technicians with proper diagnostic equipment.