Sumitomo SH350HD-6 Fault Code 87: Complete Diagnostic Guide

What is Sumitomo SH350HD-6 Fault Code 87?

Fault Code 87 on the Sumitomo SH350HD-6 excavator indicates a Swing Motor Brake Solenoid Valve Circuit Malfunction. This code is triggered when the Electronic Control Module (ECM) detects an abnormal electrical signal or voltage drop in the circuit controlling the swing motor brake release solenoid.

The swing brake solenoid is critical for safe excavator operation, as it controls the hydraulic release of the swing motor parking brake. When functioning properly, this solenoid valve receives a 12-24V signal from the ECM to release the brake during swing operations and re-engages automatically when swing motion stops. On the SH350HD-6, this system is particularly important because the machine's heavy counterweight requires precise brake control to prevent unintended swing movement during operation or transport.

Common Symptoms

When Code 87 is active on your Sumitomo SH350HD-6, you may experience:

• Swing motor fails to rotate or operates intermittently despite joystick input
• Warning light illuminated on the instrument cluster with fault code displayed
• Swing brake remains engaged even when attempting to swing the upper structure
• Abnormal jerking or delayed response when initiating swing movements
• Machine may enter reduced performance mode limiting swing speed or function entirely

Potential Causes

For used SH350HD-6 excavators, Code 87 typically results from:

• Damaged or corroded wiring harness between the ECM and swing brake solenoid (common wear point near the swing bearing)
• Failed swing brake solenoid valve due to internal coil burnout or mechanical seizure
• Loose or corroded electrical connectors at the solenoid valve or ECM terminals
• Shorted or open circuit in the solenoid control wire caused by harness rubbing against frame components
• Low voltage supply from deteriorated battery connections or failing alternator
• ECM internal driver circuit failure (less common but possible in high-hour machines)

How to Troubleshoot and Fix Code 87

Step 1: Visual Inspection Begin by inspecting the swing brake solenoid valve located on the swing motor assembly. Check for physical damage, oil contamination on electrical connectors, and verify the wiring harness routing from the solenoid to the main chassis. On used excavators, pay special attention to harness routing near the swing bearing center joint where cables flex during rotation—this is a common failure point.

Step 2: Electrical Testing Using a digital multimeter (DMM), disconnect the solenoid connector and measure resistance across the solenoid coil terminals. Typical resistance should be 12-25 ohms (consult your service manual for exact specifications). If the reading shows infinite resistance (open circuit) or near-zero (short circuit), replace the solenoid. Next, check for supply voltage at the harness connector with ignition on—you should see battery voltage (12-24V depending on system).

Step 3: Harness Continuity Check With the solenoid disconnected, test continuity between the ECM connector and the solenoid harness connector using your multimeter. Check both the power supply wire and ground return path. Resistance should be less than 1 ohm for good connections. Inspect connectors for corrosion, bent pins, or moisture intrusion—common issues in excavators operating in wet conditions.

Step 4: Component Replacement and Verification If testing confirms a faulty solenoid, replace it with a genuine Sumitomo part or quality aftermarket equivalent. After replacement, clear the fault code using diagnostic software compatible with Sumitomo equipment (such as SCS software or equivalent scan tool). Cycle the swing function multiple times and verify the code does not return.

Professional Disclaimer: While these diagnostic steps are appropriate for experienced heavy equipment mechanics, complex electrical issues or ECM-related faults may require factory-trained technicians with specialized diagnostic equipment. Always consult the official Sumitomo service manual and follow proper lockout/tagout procedures before performing electrical diagnostics.