Komatsu PC800SE-7 Fault Code H-19: Complete Diagnostic Guide

What is Komatsu PC800SE-7 Fault Code H-19?

Fault Code H-19 indicates a hydraulic oil temperature sensor circuit malfunction in the Komatsu PC800SE-7 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 (usually 0.5-4.5V).

The hydraulic oil temperature sensor is critical for this machine's performance because it allows the ECM to monitor hydraulic system health and prevent overheating damage. When this sensor fails, the control system cannot accurately assess whether the hydraulic oil is within safe operating temperatures (typically 40-80°C), potentially leading to component damage or reduced machine efficiency. For the PC800SE-7's high-capacity hydraulic system, maintaining proper temperature monitoring is essential for protecting pumps, motors, and cylinder seals.

Common Symptoms

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

• Hydraulic temperature warning light illuminated on the monitor panel
• Reduced hydraulic performance or machine entering derate mode to protect components
• Inaccurate temperature readings displayed on the monitor (showing extremely high, low, or erratic values)
• Cooling fan running continuously at high speed regardless of actual oil temperature
• Intermittent loss of hydraulic power during operation, especially in used machines with corroded connections

Potential Causes

The most common technical reasons for H-19 in used PC800SE-7 excavators include:

• Failed hydraulic oil temperature sensor due to age, thermal cycling, or internal element degradation
• Damaged or corroded wiring harness between the sensor and ECM, particularly at connector pins
• Harness chafing at known rub points near the hydraulic tank mounting brackets or along the main boom
• Loose or corroded electrical connectors at the sensor or ECM interface (common in high-hour machines)
• ECM internal circuit failure (rare, 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 sensor body for physical damage, oil leaks, or corrosion. Check the wiring harness from sensor to ECM for obvious damage, chafing, or worn insulation—pay special attention to areas where the harness contacts metal frames or moves with machine articulation.

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

Step 3: Advanced Diagnostics Connect Komatsu KOMTRAX diagnostic software or compatible scan tool to read live sensor data. Monitor temperature readings while warming the hydraulic system. For used excavators, remove and inspect connector pins for corrosion or bent terminals—clean with electrical contact cleaner and apply dielectric grease. If sensor readings are erratic, check hydraulic oil condition; contaminated oil can coat the sensor element affecting accuracy.

Step 4: Component Replacement If testing confirms sensor failure, replace with genuine Komatsu hydraulic temperature sensor (Part #6732-81-3140 or equivalent for PC800SE-7). When installing, ensure proper torque specifications (typically 15-20 N⋅m) and use new sealing washers. Clear fault codes and perform a complete system test cycle.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number. Complex electrical issues should be diagnosed by certified technicians with proper diagnostic equipment.