Komatsu PC800SE-8R Fault Code H-19: Complete Diagnostic Guide

What is Komatsu PC800SE-8R Fault Code H-19?

Fault Code H-19 indicates a hydraulic oil temperature sensor circuit malfunction in the Komatsu PC800SE-8R excavator. This code is triggered when the Electronic Control Module (ECM) detects an abnormal voltage signal from the hydraulic oil temperature sensor, typically indicating an open circuit, short circuit, or sensor reading outside the normal operating range.

The hydraulic oil temperature sensor is critical for the PC800SE-8R's performance management system. It monitors the temperature of hydraulic fluid flowing through the system, allowing the ECM to adjust pump output, activate cooling fans, and prevent overheating damage to expensive hydraulic components. When this sensor fails, the machine may enter a protective derate mode or display inaccurate temperature readings, potentially leading to catastrophic hydraulic system failure if ignored.

Common Symptoms

When Code H-19 is active, operators typically experience:

• Hydraulic oil temperature warning light illuminated on the instrument panel
• Reduced machine performance or automatic power derate to protect the hydraulic system
• Erratic or frozen temperature gauge readings on the monitor display
• Cooling fan running continuously at high speed regardless of actual oil temperature
• Intermittent code activation, especially during machine warm-up or under heavy loads

Potential Causes

The most common technical causes for H-19 on used PC800SE-8R excavators include:

• Faulty hydraulic oil temperature sensor due to age-related degradation or thermal cycling damage
• Damaged wiring harness near the hydraulic tank, particularly at known rub points where the harness contacts the frame
• Corroded or loose electrical connectors at the sensor or ECM interface
• ECM internal fault affecting the sensor input circuit (less common)
• Contaminated hydraulic oil causing sensor element fouling or coating
• Previous repair attempts using incorrect sensor specifications or aftermarket parts

How to Troubleshoot and Fix Code H-19

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor on the hydraulic tank. Inspect the sensor connector for corrosion, oil contamination, bent pins, or moisture intrusion. On used excavators, check the wiring harness routing for signs of chafing, especially where it passes near moving components or sharp edges.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance at ambient temperature (typically 2,000-3,000 ohms at 20°C, but verify against Komatsu specifications). Check for continuity in the wiring harness between the sensor connector and the ECM. Measure voltage supply from the ECM (usually 5V reference voltage) with the ignition on.

Step 3: Sensor Replacement and Verification If resistance values are out of specification or the harness shows damage, replace the faulty component using genuine Komatsu parts. For used machines, always apply dielectric grease to connectors to prevent future corrosion. Clear the fault code using Komatsu diagnostic software (KOMTRAX or compatible scan tool) and monitor for recurrence during a full operating cycle.

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