Komatsu PC220-10 Fault Code H-5: Complete Diagnostic Guide

What is Komatsu PC220-10 Fault Code H-5?

Fault Code H-5 on the Komatsu PC220-10 excavator indicates a hydraulic oil temperature sensor malfunction or abnormally high hydraulic oil temperature. This code is triggered when the Engine Control Module (ECM) or hydraulic monitoring system detects voltage irregularities from the hydraulic oil temperature sensor or when oil temperature exceeds safe operating thresholds (typically above 110-120°C/230-248°F).

This fault is critical for the PC220-10's performance because excessive hydraulic temperatures can cause rapid degradation of hydraulic fluid, damage seals and hoses, reduce system efficiency, and potentially lead to catastrophic pump or motor failure. The machine may automatically enter derate mode to protect components.

Common Symptoms

When Code H-5 is active, operators typically experience:

• Hydraulic oil temperature warning lamp illuminated on the instrument panel (amber or red)
• Reduced hydraulic power or sluggish boom/arm/bucket response as the system enters protective derate
• Audible warning alarm sounding in the cab when temperature thresholds are exceeded
• Increased cycle times during operation due to diminished hydraulic flow
• Visible smoke or burning smell from the hydraulic tank area in severe overheating cases

Potential Causes

The most common technical causes for H-5 on used PC220-10 excavators include:

• Faulty hydraulic oil temperature sensor – sensor drift or internal failure producing incorrect voltage signals (most common on machines with 5,000+ hours)
• Damaged wiring harness – chafing, pinching, or corrosion at connector points near the hydraulic tank where vibration and heat are concentrated
• Actual hydraulic system overheating – caused by plugged hydraulic oil cooler, low coolant levels, failed cooling fan, or restricted airflow from debris buildup
• Contaminated or low hydraulic oil – insufficient fluid levels or degraded oil unable to dissipate heat effectively
• ECM calibration issues – rare, but incorrect temperature parameter settings in older software versions

How to Troubleshoot and Fix Code H-5

Step 1: Initial Visual Inspection Check hydraulic oil level using the sight glass (machine must be level, cylinders retracted). Inspect the hydraulic oil cooler for external debris, bent fins, or blockages. Examine wiring around the hydraulic tank temperature sensor (typically located on tank side or return line) for visible damage, connector corrosion, or harness wear from rubbing against tank edges—a known issue on used machines.

Step 2: Sensor and Circuit Testing Using a digital multimeter, disconnect the temperature sensor connector and measure resistance across sensor terminals. At 25°C (77°F), resistance should typically read 2,000-3,000 ohms (consult service manual for exact specs). Check voltage supply from the ECM to the sensor (should be approximately 5V reference). Inspect ground continuity between sensor ground and chassis—corrosion at ground points is common on older excavators.

Step 3: Functional Testing and Part Replacement If sensor readings are out of specification, replace the hydraulic oil temperature sensor (Komatsu part number varies by serial range). For used excavators, before installing new sensors, thoroughly clean connector pins with electrical contact cleaner and apply dielectric grease to prevent future corrosion. Clear the fault code using Komatsu diagnostic software (KOMTRAX) or compatible scan tool, then monitor during operation.

Critical Note for Used Equipment: On high-hour machines, simultaneously verify actual hydraulic temperature with an infrared thermometer at the tank to rule out genuine overheating versus sensor failure. Check hydraulic filter condition and consider full system fluid analysis.

---

Disclaimer: This guide provides general troubleshooting procedures. Always consult the Komatsu PC220-10 service manual for your specific serial number and seek qualified technician assistance for complex repairs. Improper diagnostics may cause equipment damage or safety hazards.