Sumitomo SH300-6 Fault Code 1093: Complete Diagnostic Guide

What is Sumitomo SH300-6 Fault Code 1093?

Fault Code 1093 on the Sumitomo SH300-6 excavator indicates a "Pump Control Solenoid Valve Circuit Malfunction" in the hydraulic system's electronic control unit (ECU). This diagnostic trouble code (DTC) is triggered when the engine control module (ECM) detects abnormal voltage or resistance in the electrical circuit that controls the main hydraulic pump's displacement solenoid valve.

The pump control solenoid is critical for regulating hydraulic flow and pressure based on operator input and load demands. When this circuit fails, the excavator's variable displacement pump cannot properly adjust output, directly impacting fuel efficiency, hydraulic response, and overall machine performance. On used SH300-6 models, this code frequently appears due to age-related electrical degradation rather than actual solenoid failure.

Common Symptoms

When Code 1093 is active, operators typically experience:

• Reduced hydraulic power across all functions (boom, arm, bucket, swing)
• Intermittent or complete loss of fine control during precision work
• Engine rpm fluctuations or hunting at idle due to pump control inconsistencies
• Illuminated warning lamp on the instrument cluster (yellow hydraulic symbol)
• Machine entering derate mode, limiting maximum engine output to protect the hydraulic system

Potential Causes

The most common technical causes for Code 1093 on used SH300-6 excavators include:

• Corroded or loose connector pins at the pump solenoid valve (exposure to moisture and vibration)
• Damaged wiring harness between the ECM and solenoid, particularly at flex points near the pump mounting
• Failed pump control solenoid valve coil (internal short or open circuit)
• Contaminated hydraulic oil causing the solenoid spool to stick, increasing electrical load
• ECM internal fault (rare, but possible on high-hour machines)
• Voltage supply issues from the main power harness or ground connections

How to Troubleshoot and Fix Code 1093

Step 1: Visual Inspection Begin by inspecting the pump control solenoid connector located on the main hydraulic pump assembly. Check for corrosion, oil contamination, bent pins, or loose connections. On used excavators, this connector often shows green corrosion from years of moisture exposure. Clean with electrical contact cleaner and apply dielectric grease.

Step 2: Electrical Testing Using a digital multimeter (DMM), disconnect the solenoid connector and measure resistance across the solenoid coil terminals. Typical specification is 8-12 ohms at room temperature. Check the wiring harness for continuity from the ECM connector to the solenoid—resistance should be less than 1 ohm. Inspect for voltage supply (12-24V depending on system) with the key on.

Step 3: Harness and Ground Verification Trace the harness from the solenoid back to the ECM, looking for chafing points where the harness contacts the pump housing or frame. On SH300-6 models, the harness routing near the pump's rear mounting bracket is a known wear point. Verify ground continuity at both the solenoid mounting and ECM ground points—resistance should be less than 0.5 ohms.

Step 4: Component Replacement If electrical tests confirm solenoid failure, replace the pump control solenoid valve. Before installing, verify hydraulic oil cleanliness—contamination will cause premature failure. Clear codes using Sumitomo diagnostic software or a compatible CANbus scanner, then cycle the key and test all hydraulic functions under load.

Disclaimer: This guide provides general diagnostic information. Always consult the official Sumitomo service manual for your specific serial number and consider professional evaluation for complex hydraulic-electrical issues on used equipment.