Sumitomo SH350HD-6 Fault Code 602: Expert Troubleshooting Guide

What is Sumitomo SH350HD-6 Fault Code 602?

Fault Code 602 on the Sumitomo SH350HD-6 excavator indicates a Swing Motor Pressure Sensor Circuit malfunction or abnormal voltage signal. This diagnostic trouble code (DTC) is triggered when the Electronic Control Unit (ECU) detects voltage readings outside the acceptable range from the swing motor pressure sensor, typically below 0.5V or above 4.5V on a standard 5V reference circuit.

This sensor plays a critical role in monitoring hydraulic pressure during swing operations, allowing the machine's control system to optimize performance and protect the swing drive system from overload conditions. On used excavators like the SH350HD-6, this code often surfaces due to age-related wiring degradation or sensor drift, directly impacting swing function efficiency and operator safety.

Common Symptoms

When Code 602 is active, operators typically experience:

• Swing function operates erratically or with reduced speed and power
• Warning indicator illuminated on the instrument panel (typically a wrench or diagnostic lamp)
• Intermittent loss of swing control during operation, especially during rapid directional changes
• ECU enters derate mode, limiting swing motor performance to protect hydraulic components
• Abnormal hydraulic system behavior such as delayed response or jerky movements during swing operations

Potential Causes

The most common technical failures triggering Code 602 on used SH350HD-6 machines include:

• Damaged or corroded wiring harness at known rub points near the swing motor mounting area where cables flex during rotation
• Failed swing motor pressure sensor due to internal component degradation or contamination from hydraulic fluid leaks
• Connector corrosion at the sensor plug, particularly on machines operating in humid or coastal environments
• ECU voltage supply issues including compromised ground connections or damaged 5V reference circuit
• Shorted or open sensor signal wire caused by harness chafing against the swing frame or other metal components

How to Troubleshoot and Fix Code 602

Step 1: Visual Inspection Begin by thoroughly inspecting the swing motor pressure sensor and associated wiring harness. On used excavators, focus on areas where the harness routes around the swing bearing—this is a common wear point. Check for frayed insulation, exposed copper, or evidence of previous repairs with electrical tape.

Step 2: Connector and Sensor Testing Disconnect the sensor connector and inspect pins for corrosion, bent terminals, or moisture intrusion. Using a digital multimeter (DMM), measure resistance across the sensor terminals (typically 200-500 ohms for most pressure transducers). Compare readings against manufacturer specifications found in the service manual.

Step 3: Circuit Voltage Testing With ignition ON and sensor disconnected, measure supply voltage at the harness connector. You should read approximately 5.0V (±0.25V) on the reference wire. Check for proper ground continuity (less than 1 ohm resistance to chassis ground). If voltage is incorrect, trace wiring back to the ECU for breaks or shorts.

Step 4: Signal Wire Integrity Perform a voltage drop test on the signal wire while gently manipulating the harness. Intermittent voltage fluctuations indicate internal wire damage common in high-hour used machines. Pay special attention to harness routing near rotating components.

Step 5: Component Replacement If sensor readings are out of specification or harness damage is confirmed, replace faulty components using OEM or quality aftermarket parts. Before installation, apply dielectric grease to connector terminals to prevent future corrosion. After repairs, clear codes using diagnostic software (PC-based interface or compatible scan tool) and perform a functional test of swing operations under load.

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Disclaimer: This guide provides general troubleshooting procedures for Code 602. Always consult the official Sumitomo service manual for model-specific specifications and torque values. If unfamiliar with hydraulic systems or electrical diagnostics, contact a certified heavy equipment technician to avoid personal injury or further machine damage.