Kobelco SK135SRLC-2 Fault Code H013: Complete Diagnostic Guide

What is Kobelco SK135SRLC-2 Fault Code H013?

Fault Code H013 indicates a hydraulic oil temperature sensor circuit malfunction in the Kobelco SK135SRLC-2 excavator. This code triggers when the Electronic Control Unit (ECU) detects an abnormal signal from the hydraulic oil temperature sensor, which monitors the operating temperature of the hydraulic system.

The hydraulic oil temperature sensor plays a critical role in protecting the SK135SRLC-2's hydraulic system from overheating damage. When this sensor fails or provides incorrect readings, the ECU cannot properly regulate hydraulic system performance, potentially leading to component damage, reduced efficiency, and costly repairs. This monitoring system is essential for maintaining optimal viscosity and preventing accelerated wear on pumps, motors, and cylinders.

Common Symptoms

When Code H013 is active on your Kobelco SK135SRLC-2, you may experience:

• Warning light illumination on the instrument panel, often accompanied by an audible alarm
• Erratic hydraulic oil temperature gauge readings showing unrealistic values (extremely high or low)
• Reduced hydraulic system performance as the ECU enters a protective derate mode
• Intermittent loss of auxiliary functions or slower cycle times during operation
• Engine derating or shutdown in severe cases to protect hydraulic components from potential thermal damage

Potential Causes

The most common technical reasons for H013 on used SK135SRLC-2 excavators include:

• Faulty hydraulic oil temperature sensor due to internal element degradation (common after 5,000+ operating hours)
• Damaged or corroded wiring harness at the sensor connector, especially where the harness routes near the hydraulic tank
• Loose or contaminated electrical connections caused by hydraulic oil seepage around the sensor mounting area
• Broken or chafed wires at common rub points near the swing bearing or boom pivot areas
• ECU software glitches or internal ECU failure (less common but possible in high-hour machines)
• Poor grounding connections at the chassis ground points affecting sensor circuit integrity

How to Troubleshoot and Fix Code H013

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor mounted on the hydraulic oil tank. Inspect the sensor body for physical damage, oil contamination, or corrosion. Check the wiring harness from the sensor to the ECU for visible damage, chafing, or worn insulation—pay special attention to areas where cables pass through metal brackets or near moving components.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance at various temperatures. At approximately 25°C (77°F), resistance should typically read between 2,000-3,000 ohms (consult your service manual for exact specifications). Check for voltage supply at the harness connector with the sensor disconnected—you should see approximately 5 volts reference voltage from the ECU.

Step 3: Connector and Harness Evaluation For used excavators, thoroughly clean all connector pins with electrical contact cleaner and inspect for "green corrosion" common in humid environments. Test continuity from the sensor connector through to the ECU pins to identify any broken wires. Check the chassis ground connection quality, as poor grounding is frequently overlooked in older machines.

Step 4: Component Replacement and Verification If testing confirms sensor failure, replace with a genuine Kobelco sensor to ensure proper ECU communication. After replacement, clear the fault code using Kobelco diagnostic software or by disconnecting the battery for 5 minutes. Run the machine through a complete warm-up cycle and monitor for code recurrence.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Kobelco service manual for your specific machine serial number. If you're unfamiliar with electrical diagnostics or hydraulic systems, contact a certified Kobelco technician to prevent further damage or safety hazards.