Komatsu PC650LC-8R Fault Code H-19: Complete Diagnostic Guide

What is Komatsu PC650LC-8R Fault Code H-19?

Fault Code H-19 indicates a hydraulic oil temperature sensor circuit malfunction in the Komatsu PC650LC-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 failure.

The hydraulic oil temperature sensor is critical for this machine's performance because it monitors the operating temperature of the hydraulic system. The ECM uses this data to protect the hydraulic components from overheating damage and to optimize system efficiency. When this sensor fails, the machine cannot accurately monitor hydraulic temperatures, potentially leading to component damage or reduced operational safety.

Common Symptoms

When Code H-19 is active on your PC650LC-8R, operators typically experience:

• Warning light illuminated on the monitor panel, often accompanied by a hydraulic system alert
• Erratic temperature gauge readings or temperature display showing abnormal values (extremely high or low)
• Reduced hydraulic performance as the ECM may enter a protective derate mode
• Audible warning alarm sounding intermittently during operation
• Machine may continue operating but without accurate temperature monitoring, risking overheating

Potential Causes

The most common technical reasons for H-19 appearing on used PC650LC-8R excavators include:

• Damaged or corroded sensor connector – particularly common in machines with high hours due to moisture intrusion
• Failed hydraulic oil temperature sensor – sensor element degradation from heat cycling over time
• Wiring harness damage – chafing or rubbing near the hydraulic tank area where harness routing is exposed
• Broken or shorted wiring between the sensor and ECM connection points
• Corroded pins in the ECM connector or sensor plug from environmental exposure
• ECM internal fault (rare) – circuit board issues within the controller itself

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 and wiring harness for obvious damage, corrosion, oil contamination, or loose connections. On used excavators, pay special attention to harness routing points where friction against metal surfaces commonly occurs.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to check sensor 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). Check for continuity in the wiring harness from sensor to ECM. Measure voltage supply at the sensor connector with ignition on – you should see approximately 5 volts reference voltage from the ECM.

Step 3: Component Replacement and Verification If resistance values are out of specification or wiring shows damage, replace the faulty component. For used machines, always clean connector pins with electrical contact cleaner and apply dielectric grease before reconnection to prevent future corrosion. After repairs, clear the fault code using Komatsu diagnostic software (KOMTRAX) or a compatible scan tool, then operate the machine to verify the code does not return.

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