Komatsu PC200LC-7 Fault Code H-6: Technical Guide

What is Komatsu PC200LC-7 Fault Code H-6?

Fault Code H-6 indicates a malfunction in the hydraulic oil temperature sensor circuit or an abnormally high hydraulic oil temperature condition. This code is triggered when the Electronic Control Module (ECM) detects that hydraulic fluid temperature exceeds the manufacturer's safe operating threshold (typically above 110-120°C or 230-248°F) or when the temperature sensor circuit shows an electrical fault.

This fault code is critical for the PC200LC-7 because excessive hydraulic oil temperature can lead to rapid degradation of seals, reduced hydraulic efficiency, and potential catastrophic failure of pumps and motors. The hydraulic system is the lifeblood of excavator operation, and temperature regulation directly impacts component longevity and machine performance.

Common Symptoms

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

• Hydraulic warning light illuminated on the instrument cluster (amber or red depending on severity)
• Noticeably sluggish hydraulic responses, particularly during swing or boom operations
• Audible warning buzzer activating intermittently or continuously
• Reduced engine power or automatic derate mode engagement to protect the hydraulic system
• Physical smell of overheated hydraulic fluid or visible smoke from the hydraulic tank area

Potential Causes

For used PC200LC-7 excavators, the following are the most frequent culprits:

• Hydraulic oil temperature sensor failure due to age-related degradation or internal short circuit
• Damaged or corroded wiring harness connections at the temperature sensor (common rub point near the hydraulic tank)
• Actual hydraulic oil overheating caused by clogged or restricted hydraulic oil cooler fins
• Low hydraulic oil level leading to insufficient heat dissipation
• Faulty cooling fan motor or thermostat valve preventing proper oil cooling
• Malfunctioning ECM misreading sensor data (less common but possible in high-hour machines)

How to Troubleshoot and Fix Code H-6

Step 1: Visual Inspection Check the hydraulic oil level using the sight glass. Inspect the hydraulic oil cooler for debris buildup, bent fins, or blockages. On used excavators, examine the sensor wiring harness routing near the hydraulic tank for chafing, cracking, or exposed copper wiring.

Step 2: Sensor Circuit Testing Locate the hydraulic oil temperature sensor (typically mounted on the hydraulic tank or return line). Disconnect the sensor connector and use a multimeter to measure resistance. At 20°C (68°F), resistance should read approximately 2.4-2.8 kΩ. Compare readings against Komatsu specifications. Check for voltage supply at the connector (typically 5V reference from ECM).

Step 3: Functional Testing Start the machine and monitor actual hydraulic oil temperature using Komatsu diagnostic software (KOMTRAX) or an aftermarket scanner. Compare displayed temperature against a physical infrared thermometer reading at the tank. A discrepancy indicates sensor failure. If temperatures genuinely exceed 110°C, investigate cooling system functionality including fan operation and thermostat valve movement.

Step 4: Connector and Harness Inspection For used machines, pay special attention to connector corrosion. Clean contacts with electrical cleaner and apply dielectric grease. Replace any harness sections showing wear from rubbing against frame components—a known issue on PC200LC-7 models with high operational hours.

Disclaimer: This guide provides general diagnostic procedures. Always consult the official Komatsu service manual for your specific machine serial number and consult qualified heavy equipment technicians for complex electrical or hydraulic system repairs.