Komatsu PC210LC-8 Fault Code H-6: Complete Diagnostic Guide

What is Komatsu PC210LC-8 Fault Code H-6?

Fault Code H-6 on the Komatsu PC210LC-8 indicates a hydraulic oil temperature sensor circuit malfunction or abnormally high hydraulic oil temperature. This code is triggered when the Electronic Control Module (ECM) detects either a sensor voltage reading outside the normal range (typically 0.5-4.5V) or when hydraulic fluid exceeds the critical threshold of approximately 110-120°C (230-248°F).

This fault is critical for the PC210LC-8 because excessive hydraulic oil temperature accelerates component wear, degrades seal integrity, and reduces hydraulic fluid viscosity. The machine's performance becomes compromised as the hydraulic pump, control valves, and cylinder seals operate outside their optimal temperature ranges. Komatsu's monitoring system uses this code to prevent catastrophic hydraulic system failure.

Common Symptoms

• Warning lamp illumination on the instrument panel, often accompanied by an audible alarm
• Reduced hydraulic response with sluggish boom, arm, or bucket movements
• Automatic engine derate or power reduction mode to protect hydraulic components
• Visible hydraulic oil overheating with hot fluid smell or smoke from the reservoir area
• Intermittent or constant code triggering depending on whether the issue is sensor-related or actual temperature elevation

Potential Causes

Sensor and Electrical Issues:

• Failed or degraded hydraulic temperature sensor (common wear item on used machines)
• Damaged sensor wiring harness at common rub points near the hydraulic tank mounting brackets
• Corroded or loose connector pins at the sensor or ECM interface
• ECM internal fault (rare but documented in high-hour PC210LC-8 units)

Actual Hydraulic Temperature Problems:

• Clogged hydraulic oil cooler fins or internal passages (typical in dusty environments)
• Malfunctioning cooling fan or faulty fan drive motor
• Low hydraulic oil level causing insufficient heat dissipation
• Contaminated or incorrect hydraulic fluid viscosity grade
• Excessive system pressure due to worn relief valves or restricted return lines

How to Troubleshoot and Fix Code H-6

Step 1: Visual Inspection Check the hydraulic oil level in the reservoir and inspect for contamination or incorrect fluid type. Examine the oil cooler for debris blockage and clean with compressed air if necessary. Inspect the cooling fan operation during machine warm-up.

Step 2: Sensor Circuit Testing Locate the hydraulic temperature sensor on the return line near the tank. Disconnect the sensor connector and use a digital multimeter to measure resistance across the sensor terminals. At ambient temperature (20°C), resistance should read approximately 2,000-3,000 ohms depending on specifications. Compare readings against Komatsu's resistance-temperature chart in the service manual.

Step 3: Wiring and Voltage Verification With the sensor disconnected, check for supply voltage (typically 5V reference) from the ECM harness. Inspect wiring for chafing damage at the frame rail and tank mounting points—common failure areas on used PC210LC-8 excavators. Measure signal wire continuity back to the ECM connector.

Step 4: Component Replacement If sensor resistance is out of specification or wiring shows damage, replace the faulty component using genuine Komatsu parts (part number varies by serial number). For used excavators, always apply dielectric grease to connectors to prevent future corrosion. Clear codes using Komatsu diagnostic software (KTDS) and perform a operational temperature test.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu PC210LC-8 service manual and consider professional diagnostic assistance for complex electrical issues or if you lack proper testing equipment.