Komatsu PC210LC-10 Fault Code H-8: Complete Diagnostic Guide

What is Komatsu PC210LC-10 Fault Code H-8?

Fault Code H-8 indicates a malfunction in the hydraulic oil temperature sensor circuit on the Komatsu PC210LC-10 excavator. This Diagnostic Trouble Code (DTC) is triggered when the Engine Control Module (ECM) detects an abnormal voltage reading from the hydraulic oil temperature sensor, typically due to an open circuit, short circuit, or sensor failure.

The hydraulic oil temperature monitoring system is critical for the PC210LC-10's performance and longevity. This sensor helps the ECM regulate hydraulic system efficiency, prevent overheating damage to seals and hoses, and optimize fuel consumption. When this sensor fails, the machine may enter a protective derate mode to prevent catastrophic hydraulic system damage, significantly impacting productivity on the job site.

Common Symptoms

When Code H-8 is active on your Komatsu PC210LC-10, operators typically experience:

• Hydraulic oil temperature warning light illuminated on the monitor panel
• Reduced hydraulic power or sluggish boom/arm/bucket response during operation
• Audible alarm sounding intermittently or continuously from the cab
• Machine derate mode activating, limiting engine RPM and hydraulic flow
• Monitor display showing abnormal temperature readings (often maxed out or reading zero)

Potential Causes

For used Komatsu PC210LC-10 excavators, Code H-8 typically results from:

• Failed hydraulic oil temperature sensor due to age-related degradation or contamination exposure
• Damaged wiring harness from rubbing against the main pump or hydraulic tank mounting brackets (common wear point on this model)
• Corroded or loose electrical connectors at the sensor or ECM interface, especially on machines operating in wet/salty environments
• Intermittent short to ground in the sensor circuit wiring running along the left-side frame rail
• ECM internal fault (rare, but possible on high-hour machines)

How to Troubleshoot and Fix Code H-8

Step 1: Visual Inspection and Connector Check Begin by locating the hydraulic oil temperature sensor on the left side of the hydraulic tank. Disconnect the two-pin connector and inspect for corrosion, bent pins, or oil contamination. Clean contacts with electrical contact cleaner and examine the wiring harness for visible damage, particularly where it routes near the tank mounting bolts.

Step 2: Sensor Resistance Testing Using a digital multimeter (DMM), measure the sensor's resistance. At room temperature (approximately 68°F/20°C), the sensor should read between 2,000-3,000 ohms. If the reading shows infinite resistance (open circuit) or zero ohms (short circuit), replace the sensor (Komatsu Part Number: 7861-93-3320 or equivalent).

Step 3: Circuit Voltage and Wiring Verification With the sensor disconnected and ignition ON (engine OFF), measure voltage at the ECM-side harness connector. You should see approximately 5 volts on the signal wire. If voltage is absent, trace the harness back to the ECM checking for breaks, especially at common rub points near the slew bearing. On used excavators, pay special attention to harness sections with heat damage from exhaust components or abrasion from vibration.

Step 4: Clear Code and Monitor After repairs, clear the fault code using Komatsu KOMTRAX diagnostic software or a compatible diagnostic scanner. Run the machine through normal operating cycles while monitoring hydraulic temperature readings to confirm the repair resolved the issue.

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Disclaimer: This guide provides general troubleshooting information for experienced mechanics. Always consult the official Komatsu PC210LC-10 service manual and follow proper safety lockout/tagout procedures. If uncertain, contact a certified Komatsu technician for professional diagnosis and repair.