Komatsu PC800SE-8R Fault Code H-6: Complete Diagnostic Guide

What is Komatsu PC800SE-8R Fault Code H-6?

Fault Code H-6 indicates a hydraulic oil temperature sensor circuit malfunction or abnormally high hydraulic oil temperature in the Komatsu PC800SE-8R excavator. This code is triggered when the Electronic Control Module (ECM) detects either an electrical fault in the temperature sensor circuit or when hydraulic oil temperature exceeds safe operating parameters (typically above 110-120°C or 230-248°F).

This fault is critical for the PC800SE-8R because excessive hydraulic oil temperature can cause rapid degradation of seals, reduced hydraulic efficiency, and potential damage to the hydraulic pump and control valves. The machine's monitoring system uses this sensor data to protect expensive hydraulic components and maintain optimal performance under heavy loads.

Common Symptoms

When Code H-6 is active, operators typically experience:

• Hydraulic oil temperature warning light illuminated on the monitor panel
• Reduced machine performance or automatic derate mode limiting hydraulic functions
• Audible alarm sounding from the cab warning system
• Sluggish hydraulic response, particularly during high-demand operations like digging or lifting
• Visible steam or excessive heat radiating from the hydraulic oil cooler area

Potential Causes

The most common technical causes for H-6 on used PC800SE-8R excavators include:

• Hydraulic oil temperature sensor failure due to age-related degradation or contamination
• Damaged or corroded wiring harness at sensor connector points (common wear area near the hydraulic tank)
• Actual hydraulic system overheating from clogged oil cooler fins or malfunctioning cooling fan
• Low hydraulic oil level causing insufficient cooling capacity
• ECM communication errors or poor ground connections affecting sensor signal
• Contaminated hydraulic oil reducing heat dissipation efficiency
• Failed thermostat in the hydraulic cooling circuit

How to Troubleshoot and Fix Code H-6

Step 1: Visual Inspection Check hydraulic oil level using the sight glass. Inspect the temperature sensor (located on the hydraulic tank) and its wiring harness for physical damage, corrosion, or oil contamination on connectors. On used excavators, examine harness routing for rub points against frame members.

Step 2: Electrical Testing Using a digital multimeter, measure sensor resistance. The temperature sensor should read approximately 200-300 ohms at 20°C (68°F). Check for voltage supply (typically 5V reference) from the ECM to the sensor. Inspect ground circuit continuity.

Step 3: Cooling System Verification Clean the hydraulic oil cooler thoroughly, removing debris from fins. Verify cooling fan operation and thermostat function. Check hydraulic oil condition—contaminated or degraded oil should be replaced.

Step 4: Component Replacement If sensor readings are out of specification or wiring shows damage, replace the temperature sensor (Komatsu part number specific to PC800SE-8R). For used machines, always replace connector seals to prevent moisture intrusion.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual and consider professional technician assistance for complex repairs.