What is Komatsu PC100-6 Fault Code H-15?

Fault Code H-15 on the Komatsu PC100-6 excavator indicates a malfunction in the hydraulic oil temperature sensor circuit. This code triggers when the electronic control module (ECM) detects abnormal voltage readings from the temperature sensor monitoring the hydraulic oil reservoir. The sensor plays a critical role in protecting the hydraulic system by alerting operators when oil temperatures exceed safe operating limits, typically around 95-110°C (203-230°F).

For the PC100-6 model specifically, this fault affects the hydraulic temperature monitoring system, which prevents component damage from overheating. The ECM uses this sensor data to activate warning indicators and potentially limit machine performance to avoid catastrophic hydraulic pump or motor failure.

Common Symptoms

• Yellow warning light illuminated on the instrument panel, often accompanied by a temperature gauge reading abnormally high or low
• Intermittent or continuous alarm beeping from the operator cabin warning system
• Hydraulic oil temperature gauge displays erratic readings or stays at minimum/maximum positions regardless of actual operating conditions
• Machine may enter derate mode, limiting swing speed or hydraulic flow after extended operation
• In severe cases, complete system shutdown if the ECM cannot verify safe operating temperatures

Potential Causes

The H-15 code on used PC100-6 excavators typically stems from age-related deterioration. The hydraulic temperature sensor itself commonly fails due to prolonged heat exposure and thermal cycling over thousands of operating hours. Wiring harness damage is frequent near the hydraulic tank area where vibration causes insulation to wear against metal brackets.

Corroded or loose electrical connectors at the sensor or ECM connection points create intermittent high-resistance conditions. On older machines, sensor mounting threads can develop cracks, allowing hydraulic oil to contaminate the electrical connection. Less commonly, ECM internal faults in the temperature monitoring circuit can trigger false codes.

How to Troubleshoot and Fix Code H-15

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor on the return filter housing near the hydraulic tank. Inspect the wire harness from sensor to ECM for obvious damage—check for chafing at routing clips, cracked insulation, or oil contamination on connectors. Clean all electrical connectors with contact cleaner and verify tight connection.

Step 2: Electrical Testing Using a digital multimeter, measure sensor resistance with the connector disconnected. At room temperature (20°C), resistance should typically read 2.0-3.0 kΩ (consult your specific service manual for exact values). Check for open circuits (infinite resistance) or shorts (zero resistance). Measure voltage supply from the ECM—should read approximately 5 volts DC on the signal wire.

Step 3: Component Replacement If sensor resistance falls outside specifications or the harness shows damage, replace the affected component. For used excavators, always replace the connector seals even if reusing existing wiring to prevent future moisture intrusion. After replacement, clear the fault code using Komatsu diagnostic software (KOMTRAX) or a compatible OBD scanner and verify the code does not return during a 30-minute operating test.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu PC100-6 service manual and consider professional technician assistance for complex electrical diagnostics or if unfamiliar with high-voltage systems.