Sumitomo SH240-6 Fault Code 87: Complete Diagnostic Guide

What is Sumitomo SH240-6 Fault Code 87?

Fault Code 87 on the Sumitomo SH240-6 excavator indicates a malfunction in the Swing Motor Solenoid Valve Circuit. This code triggers when the Electronic Control Module (ECM) detects an abnormal electrical signal—either an open circuit, short circuit, or abnormal resistance—in the swing motor's proportional solenoid valve wiring or the solenoid itself.

The swing motor system is critical for upper structure rotation, and this fault directly impacts the excavator's ability to perform smooth, controlled swing operations. The proportional solenoid valve regulates hydraulic flow to the swing motor based on joystick input. When Code 87 activates, the ECM may limit swing function or disable it entirely to prevent hydraulic system damage or erratic machine behavior.

Common Symptoms

When Code 87 is active on your SH240-6, operators typically experience:

• Erratic or non-responsive swing operation despite normal joystick movement
• Swing function completely disabled while other hydraulic functions operate normally
• Warning lamp illuminated on the instrument panel (typically amber/yellow)
• Intermittent swing motor engagement that comes and goes during operation
• Reduced swing speed or lack of proportional control (all-or-nothing response)

Potential Causes

For used Sumitomo SH240-6 excavators, Code 87 typically stems from:

• Damaged wiring harness at the swing motor mounting area where vibration and rotation cause wire chafing
• Corroded or loose electrical connectors at the solenoid valve due to moisture intrusion
• Failed proportional solenoid coil within the swing control valve (resistance out of specification)
• Broken or frayed wires in the harness routing through the center joint/swivel area
• ECM internal driver circuit failure (less common, but possible in high-hour machines)
• Poor ground connection at the swing motor assembly or valve body

How to Troubleshoot and Fix Code 87

Step 1: Visual Inspection Begin by inspecting the wiring harness from the ECM to the swing motor solenoid valve. On used SH240-6 models, focus on the harness routing through the center joint swivel where cables pass from the lower frame to the upper structure. Look for abraded insulation, pinched wires, or damaged connectors. Check for oil contamination or corrosion on connector pins.

Step 2: Electrical Testing Using a digital multimeter, disconnect the solenoid valve connector and measure coil resistance. Typical specification is 10-30 ohms (consult your service manual for exact values). Test for short to ground by checking continuity between each solenoid terminal and the valve body (should read infinite resistance). Verify supply voltage at the connector with ignition on—should read approximately 12-24V DC depending on your machine's electrical system.

Step 3: Harness Continuity Check With the solenoid connector and ECM connector both disconnected, test continuity through the entire harness. Any reading above 2-3 ohms indicates excessive resistance from corroded connections or damaged wire strands. Pay special attention to ground circuits, as poor grounding is common in used machines.

Step 4: Component Replacement If the solenoid coil tests out of specification, replace the proportional solenoid valve assembly. For used excavators, always apply dielectric grease to connectors during reassembly to prevent future corrosion. If wiring is damaged, repair using OEM-spec wire and proper weatherproof connectors—avoid temporary fixes with electrical tape.

Step 5: Clear Code and Test After repairs, clear the fault code using Sumitomo diagnostic software or by disconnecting the battery for 5+ minutes. Operate the swing function through full range of motion and monitor for code recurrence.

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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 software version. For complex electrical issues or ECM replacement, seek assistance from a certified Sumitomo technician or qualified heavy equipment electrician.