Komatsu PC800LC-8R Fault Code H-19: Complete Diagnostic Guide

What is Komatsu PC800LC-8R Fault Code H-19?

Fault Code H-19 indicates a hydraulic oil temperature sensor circuit malfunction in the Komatsu PC800LC-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 plays a critical role in protecting the PC800LC-8R's hydraulic system by monitoring fluid temperature and preventing overheating damage. When this sensor fails or provides incorrect readings, the ECM cannot accurately manage hydraulic system performance, potentially leading to reduced efficiency, component wear, or catastrophic hydraulic failure. For a machine of this size and complexity, maintaining proper hydraulic temperature monitoring is essential for both performance and longevity.

Common Symptoms

When Code H-19 is active on your PC800LC-8R, you may experience:

• Warning light illuminated on the monitor panel, often accompanied by an audible alarm
• Hydraulic system derate or reduced hydraulic flow to prevent potential overheating damage
• Inaccurate or erratic hydraulic oil temperature readings displayed on the operator monitor (may show extremely high or low values)
• Machine performance limitations, including slower cycle times or restricted attachment functions
• Intermittent code activation, especially during cold starts or after extended operation periods

Potential Causes

Several factors can trigger Code H-19 on used PC800LC-8R excavators:

• Faulty hydraulic oil temperature sensor due to age-related degradation or internal component failure
• Damaged wiring harness or corroded connectors between the sensor and ECM, particularly at known rub points near the hydraulic tank
• Open or short circuit in the sensor signal wire caused by chafing against frame components
• Corroded or loose connector pins at the sensor or ECM connection points (common in high-hour used machines)
• ECM internal fault affecting the sensor input circuit (less common but possible in older units)
• Contaminated hydraulic oil causing sensor element fouling or coating

How to Troubleshoot and Fix Code H-19

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor (typically mounted on the hydraulic tank). Inspect the wiring harness from the sensor to the ECM for visible damage, chafing, or wear points. On used excavators, pay special attention to areas where harnesses route near moving components or sharp edges. Check all connector pins for corrosion, bent pins, or oil contamination.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure resistance across the sensor terminals. Compare readings against Komatsu specifications (typically 200-400 ohms at 20°C, varying with temperature). Check for continuity in the wiring harness between the sensor connector and ECM. Measure voltage supply from the ECM to the sensor (should be approximately 5 volts reference voltage).

Step 3: Sensor and Circuit Verification If resistance values are out of specification, replace the hydraulic oil temperature sensor with a genuine Komatsu part. If wiring shows damage, repair or replace the affected harness section, ensuring proper routing away from friction points. Clear the fault code using Komatsu diagnostic software (KOMTRAX) or a compatible scan tool, then operate the machine to verify the repair.

Step 4: Advanced Diagnostics For persistent codes after sensor replacement, inspect ECM connector terminals for corrosion or damage. Consider testing with a known-good sensor to eliminate parts-related issues. Check hydraulic oil condition—contaminated oil may indicate broader system problems requiring attention.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu PC800LC-8R service manual and consider professional assistance from certified Komatsu technicians for complex repairs or if you're uncertain about any procedure.