What is Komatsu PC200-10 Fault Code H-19?

Fault Code H-19 on the Komatsu PC200-10 excavator indicates a hydraulic oil temperature sensor malfunction in the hydraulic tank. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects an abnormal voltage signal from the hydraulic oil temperature sensor, suggesting either an open circuit, short circuit, or sensor reading outside acceptable parameters.

This code is critical for the PC200-10's performance because the hydraulic oil temperature directly affects the machine's operational efficiency and component longevity. The ECM uses temperature data to regulate hydraulic system functions, prevent overheating, and protect seals, pumps, and valves from thermal damage. Ignoring this fault can lead to reduced hydraulic performance, accelerated component wear, and potential catastrophic hydraulic system failure on used machines already experiencing wear.

Common Symptoms

• Hydraulic oil temperature warning light illuminated on the monitor panel
• Reduced hydraulic power or sluggish boom/arm/bucket movements, especially under load
• Intermittent warning alarms even when the hydraulic oil feels cool to the touch
• ECM derate mode activation limiting engine RPM or hydraulic flow as a protective measure
• Inaccurate temperature readings displayed on the monitor (showing extremely high or low values that don't match actual conditions)

Potential Causes

The most common causes of H-19 on used PC200-10 excavators include:

• Failed hydraulic oil temperature sensor due to age, thermal cycling, or internal element deterioration
• Corroded or damaged wiring connectors at the sensor or ECM connection points (common on machines operating in wet or corrosive environments)
• Wiring harness damage from rubbing against the hydraulic tank or chassis, particularly near mounting brackets
• Intermittent open circuits caused by broken wire strands inside the insulation from vibration stress
• ECM internal fault (rare, but possible on high-hour used machines)
• Poor ground connection at the sensor or ECM grounding point

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 or bottom). Inspect the sensor body for physical damage, oil contamination on the connector, or corrosion. Check the entire wiring harness from sensor to ECM for signs of abrasion, pinching, or exposure to hydraulic fluid.

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 room temperature, varying with actual oil temperature). Check for voltage supply at the harness connector (usually 5V reference voltage from the ECM). Test for continuity between sensor connector and ECM pins, and verify ground integrity.

Step 3: Component Replacement and Verification If sensor resistance is out of specification or harness testing reveals open/short circuits, replace the faulty component. For used excavators, thoroughly clean all 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 scanner, and monitor for code recurrence during a full operational cycle.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific serial number and seek qualified technician assistance for complex electrical diagnostics or if you're uncertain about any procedure.