Sumitomo SH210-5 Fault Code 87: Technical Diagnosis and Repair Guide

What is Sumitomo SH210-5 Fault Code 87?

Fault Code 87 on the Sumitomo SH210-5 excavator indicates a malfunction in the swing motor speed sensor circuit or an abnormal signal from the swing rotation detection system. This code is triggered when the Electronic Control Module (ECM) detects an irregular voltage pattern, open circuit, or signal dropout from the swing speed sensor that monitors the upper structure's rotational velocity.

This fault is critical because the swing motor speed sensor provides essential feedback to the hydraulic control system for proper swing acceleration, deceleration, and load management. When this sensor fails or sends erratic signals, the machine may enter a protective derate mode to prevent damage to the swing machinery and hydraulic components. For used excavators, this code frequently appears due to sensor degradation, harness wear from continuous rotation cycles, or contamination in the slip ring assembly.

Common Symptoms

When Code 87 is active on your SH210-5, operators typically experience:

• Erratic swing operation with inconsistent acceleration or jerky rotation during slewing maneuvers
• Reduced swing speed or complete loss of upper structure rotation in severe cases
• Warning indicator illuminated on the instrument panel (often accompanied by an audible alarm)
• Intermittent code appearance that comes and goes during specific swing directions or speeds
• Hydraulic system derate where other functions may also feel sluggish or underpowered

Potential Causes

The most common technical failures triggering Code 87 in used SH210-5 excavators include:

• Swing motor speed sensor failure due to internal component degradation or bearing contamination
• Damaged wiring harness in the center joint area where cables route through the swing circle (known rub point)
• Corroded or loose electrical connectors at the sensor or ECM connections
• Slip ring assembly wear causing intermittent signal interruption during rotation
• ECM internal fault (rare) where the controller cannot properly process sensor signals
• Voltage supply issues from damaged power wires or poor grounding connections

How to Troubleshoot and Fix Code 87

Step 1: Visual Inspection Begin by examining the swing motor speed sensor mounted on the swing motor assembly. Check for physical damage, oil contamination, or loose mounting bolts. Inspect the wiring harness from the sensor through the center joint to the ECM, looking specifically for chafing, cuts, or exposure at rotation points common in used machines.

Step 2: Electrical Testing Using a digital multimeter, measure resistance across the sensor terminals (typically 800-1200 ohms for this model). Check supply voltage at the sensor connector (should read 8-12V with ignition on). Inspect connector pins for corrosion or bent terminals—a frequent issue in older excavators.

Step 3: Signal Testing Connect Sumitomo diagnostic software or a compatible scan tool to monitor real-time sensor output while manually rotating the swing motor shaft. The signal should show consistent pulses. Erratic readings indicate sensor replacement; no signal suggests harness or ECM issues.

Step 4: Repair Actions For used excavators, always clean and apply dielectric grease to all connectors before replacing components. Replace the sensor if testing confirms failure. Repair or reroute damaged harnesses away from friction points. Clear codes and perform a swing function test under load.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Sumitomo service manual and consider professional diagnostic assistance for complex electrical issues or if unfamiliar with high-voltage systems.