Kobelco SK135SR-2 Fault Code R024: Complete Diagnostic Guide

What is Kobelco SK135SR-2 Fault Code R024?

Fault Code R024 indicates a malfunction in the hydraulic oil temperature sensor circuit or an abnormal temperature reading in the hydraulic system. This code is triggered when the Engine Control Module (ECM) detects a voltage signal from the temperature sensor that falls outside the acceptable operating range, or when hydraulic oil temperatures exceed safe operational limits.

The hydraulic oil temperature sensor monitors the thermal condition of the hydraulic fluid, which is critical for maintaining proper viscosity and system efficiency. On the SK135SR-2, this sensor feeds real-time data to the ECM, which adjusts machine performance to prevent component damage. Ignoring this fault can lead to accelerated wear on hydraulic pumps, motors, and seals, particularly in used excavators where the hydraulic system may already show age-related degradation.

Common Symptoms

When Code R024 is active, operators typically experience:

• Warning light illumination on the instrument cluster, often accompanied by an audible alarm
• Reduced hydraulic performance, including slower cycle times and decreased digging force
• Intermittent power loss or automatic derate mode activation to protect system components
• Erratic gauge readings showing fluctuating or abnormally high hydraulic oil temperatures
• Sluggish machine response during cold starts or after extended idle periods

Potential Causes

The most common technical reasons for R024 appearing on used SK135SR-2 excavators include:

• Faulty hydraulic oil temperature sensor due to internal component failure or contamination exposure
• Damaged wiring harness or corroded connectors, particularly at the sensor connection point near the hydraulic tank
• Actual hydraulic oil overheating caused by restricted cooler flow, low oil levels, or worn hydraulic pumps generating excessive heat
• ECM communication errors resulting from voltage irregularities or poor ground connections
• Contaminated hydraulic oil with degraded thermal properties affecting accurate temperature readings
• Worn sensor mounting points allowing vibration-induced connection failures common in older machines

How to Troubleshoot and Fix Code R024

Step 1: Visual Inspection Begin by examining the hydraulic oil temperature sensor location near the hydraulic tank. Check for physical damage, oil leaks, or loose connections. Inspect the wiring harness for rubbing points against the frame, particularly where it routes along the tank assembly—a common wear point on used SK135SR-2 models.

Step 2: Electrical Testing Using a digital multimeter, check sensor resistance. The typical range for Kobelco temperature sensors at ambient temperature (68°F/20°C) is 2,000-3,000 ohms, varying with temperature. Verify supply voltage at the sensor connector (should read approximately 5 volts with key on, engine off). Check for continuity between the sensor ground and chassis ground.

Step 3: Monitor Actual Temperature Use an infrared thermometer to measure actual hydraulic oil temperature at the tank. Compare this reading with the display value. A variance greater than 20°F indicates sensor calibration issues. For used excavators, also verify the hydraulic oil cooler isn't blocked with debris and confirm proper oil level.

Step 4: Connector and Harness Repair Clean all connector pins with electrical contact cleaner and apply dielectric grease to prevent corrosion—critical for machines operating in harsh environments. Repair any harness damage with heat-shrink connectors rated for vibration resistance.

Step 5: Component Replacement If diagnostics confirm sensor failure, replace with a genuine Kobelco temperature sensor (Part No. YN52S00037P1 or equivalent). After replacement, clear codes using Kobelco diagnostic software and perform a system function test.

Disclaimer: This guide provides general diagnostic procedures. Hydraulic systems operate under high pressure and temperature. Always consult your Kobelco service manual and consider professional technician assistance for complex repairs, especially on used equipment with unknown service history.