Sumitomo SH290-5 Fault Code 108: Complete Diagnostic Guide

What is Sumitomo SH290-5 Fault Code 108?

Fault Code 108 on the Sumitomo SH290-5 excavator indicates a Hydraulic Oil Temperature Sensor Circuit malfunction. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects an abnormal voltage signal from the hydraulic oil temperature sensor, which monitors the working temperature of the hydraulic fluid in the main system.

This sensor is critical for the SH290-5's performance management system. The ECM uses temperature data to adjust hydraulic pump output, prevent overheating damage to seals and hoses, and protect the machine from operating outside safe temperature parameters. When Code 108 activates, the system may enter a protective derate mode to prevent catastrophic hydraulic system failure.

Common Symptoms

Operators experiencing Code 108 will typically notice:

• Warning light illuminated on the instrument panel (often a hydraulic temperature icon or check engine light)
• Reduced hydraulic power or sluggish boom/arm/bucket response as the ECM limits pump flow
• Intermittent or constant alarm beeping from the cab warning system
• Erratic temperature gauge readings showing unrealistic spikes or drops in hydraulic oil temperature
• Machine may enter limp mode, restricting travel speed and hydraulic functions to protect components

Potential Causes

The most common technical reasons for Code 108 on used SH290-5 excavators include:

• Failed hydraulic oil temperature sensor due to age, heat cycling, or internal element degradation
• Damaged or corroded wiring harness at connector points, especially near the hydraulic tank where exposure to oil mist and heat is constant
• Broken or frayed sensor wires at known rub points along the main chassis frame near the swing bearing
• Corroded connector pins at the sensor plug or ECM interface due to moisture intrusion
• ECM internal fault (rare) causing misreading of sensor voltage signals
• Poor ground connection on sensor circuit causing voltage fluctuations

How to Troubleshoot and Fix Code 108

Step 1: Visual Inspection Begin with a thorough inspection of the hydraulic oil temperature sensor located on the hydraulic tank. Check the wiring harness from sensor to ECM for obvious damage, oil contamination, chafing against frame components, or burnt insulation. On used excavators, pay special attention to harness routing near the swing circle where repetitive motion causes wear.

Step 2: Connector and Ground Testing Disconnect the sensor connector and inspect pins for corrosion, bent contacts, or oil intrusion. Clean with electrical contact cleaner if necessary. Using a digital multimeter (DMM), verify ground continuity by testing resistance from sensor ground pin to chassis ground (should read less than 1 ohm).

Step 3: Sensor Resistance Check With sensor disconnected and at ambient temperature, measure resistance across sensor terminals. Typical specification for this NTC (Negative Temperature Coefficient) sensor is approximately 2,000-3,000 ohms at 20°C (68°F). Compare readings to Sumitomo's service manual specifications. An open circuit (infinite resistance) or short (near-zero resistance) indicates sensor failure.

Step 4: Circuit Voltage Testing Reconnect sensor and backprobe the signal wire at the ECM connector using a DMM. With ignition on, voltage should typically read between 0.5-4.5 volts depending on oil temperature. If voltage reads 5V constantly or 0V, suspect wiring issues or ECM problems.

Step 5: Component Replacement If sensor tests faulty, replace with a genuine Sumitomo or OEM-equivalent temperature sensor. For used machines, always replace the connector pigtail simultaneously if any corrosion is present. After replacement, clear codes using Sumitomo diagnostic software or compatible scan tool and verify repair with a test cycle.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Sumitomo service manual for your specific serial number and seek assistance from certified heavy equipment technicians for complex electrical diagnostics or repairs.