Komatsu PC800-8R Fault Code H-19: Complete Diagnostic Guide

What is Komatsu PC800-8R Fault Code H-19?

Fault Code H-19 indicates a hydraulic oil temperature sensor circuit malfunction in the Komatsu PC800-8R excavator. This code triggers when the Electronic Control Module (ECM) detects an abnormal voltage signal from the hydraulic oil temperature sensor, which monitors the operating temperature of the hydraulic system fluid.

The hydraulic oil temperature sensor plays a critical role in protecting the PC800-8R's hydraulic system from overheating damage. When functioning properly, it allows the ECM to adjust pump output and activate cooling systems as needed. On this 80-ton class excavator, maintaining optimal hydraulic temperatures (typically 50-80°C) is essential for preserving seal integrity, preventing fluid degradation, and ensuring consistent hydraulic performance across all functions.

Common Symptoms

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

• Warning light illumination on the monitor panel with hydraulic system alert
• Inaccurate or erratic temperature readings displayed on the cab monitor
• Reduced hydraulic performance as the system may enter protective derate mode
• Cooling fan running continuously regardless of actual hydraulic temperature
• Intermittent code activation during machine warm-up or under heavy load conditions

Potential Causes

The most common technical causes for H-19 on used PC800-8R excavators include:

• Sensor failure due to age-related internal resistance drift or element degradation
• Wiring harness damage at known rub points near the hydraulic tank mounting brackets
• Corroded or loose connector pins at the sensor plug (3-pin connector)
• Damaged sensor threads causing poor thermal contact with hydraulic tank
• ECM internal circuit issues (less common, typically after electrical surge events)
• Contaminated sensor tip from metallic debris or sludge buildup in older machines

How to Troubleshoot and Fix Code H-19

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor on the hydraulic tank (typically mounted on the side panel). Inspect the wiring harness from sensor to ECM for chafing, cuts, or heat damage. On used excavators, check connector pins for corrosion, bent terminals, or oil contamination—common issues after 5,000+ operating hours.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. At 20°C, resistance should typically read 2,000-3,000 ohms (consult service manual for exact specifications). Check voltage supply at the harness connector—should read approximately 5V with ignition on. Measure continuity from connector to ECM to identify open circuits.

Step 3: Component Replacement If sensor resistance is out of specification or harness shows damage, replace the faulty component. When installing a new temperature sensor, apply anti-seize compound to threads and torque to 15-20 Nm. Clear codes using Komatsu diagnostic software (KOMTRAX) or compatible scan tool, then monitor during a complete heat cycle.

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