Komatsu PC70-8 Fault Code E-15: Complete Diagnostic Guide

What is Komatsu PC70-8 Fault Code E-15?

Fault Code E-15 on the Komatsu PC70-8 indicates a malfunction in the hydraulic oil temperature sensor circuit. This code triggers when the Engine Control Module (ECM) detects an abnormal voltage signal from the temperature sensor monitoring the hydraulic oil system.

The hydraulic oil temperature sensor plays a critical role in protecting the PC70-8's hydraulic system by monitoring operating temperatures. When oil temperatures exceed safe limits or the sensor circuit fails, the ECM logs this fault to prevent potential damage to hydraulic components, seals, and pumps. For this compact excavator model, maintaining proper hydraulic temperature monitoring is essential for optimal performance and component longevity.

Common Symptoms

When Code E-15 is active, operators typically experience:

• Warning light illuminated on the instrument panel (typically a hydraulic system indicator)
• Erratic or incorrect hydraulic oil temperature readings on the display
• Reduced hydraulic performance or machine entering a protective derate mode
• Intermittent loss of temperature monitoring functionality
• In severe cases, the machine may limit operations to prevent overheating damage

Potential Causes

The most common technical reasons for E-15 on used PC70-8 excavators include:

• Faulty hydraulic oil temperature sensor due to age-related degradation or contamination
• Damaged or corroded wiring harness connections at the sensor plug
• Chafed wires along the harness routing near the hydraulic tank (common wear point on this model)
• Corroded or loose ground connections affecting sensor circuit integrity
• Failed ECM input circuit (rare, but possible in high-hour machines)
• Contaminated hydraulic oil causing sensor element failure

How to Troubleshoot and Fix Code E-15

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor on the hydraulic tank. Inspect the sensor connector for corrosion, oil contamination, or loose pins. Check the wiring harness for visible damage, especially where it routes near moving components or sharp edges—a common failure point on used excavators.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance. At room temperature (20°C/68°F), resistance should typically read between 2,000-3,000 ohms (consult your service manual for exact specifications). Test the harness voltage at the connector with the ignition on—you should see approximately 5 volts reference voltage from the ECM.

Step 3: Circuit Verification Check for continuity between the sensor connector and the ECM pins. Inspect for short circuits to ground or power. On used machines, pay special attention to harness sections that may have experienced friction wear from vibration over thousands of operating hours.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu part to ensure proper resistance curves. After replacement, clear the fault code using Komatsu diagnostic software (KOMTRAX or compatible scan tool) and verify the system operates normally under load.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number and consider professional assistance for complex electrical diagnostics.