What is Komatsu PC200LC-7 Fault Code E205?

Komatsu PC200LC-7 Fault Code E205 indicates a malfunction in the hydraulic oil temperature sensor circuit. This code is triggered when the engine control module (ECM) detects an abnormal voltage signal from the hydraulic oil temperature sensor, which monitors the operating temperature of the machine's hydraulic system.

The hydraulic oil temperature sensor plays a critical role in the PC200LC-7's performance monitoring system. It sends continuous voltage signals to the ECM, allowing the controller to protect the hydraulic system from overheating damage. When this sensor circuit fails or provides readings outside the normal range (typically 0.5-4.5 volts), the ECM logs fault code E205 and may implement protective measures. For used excavators, this sensor and its wiring are particularly vulnerable to heat damage, corrosion, and connector degradation after years of operation in harsh environments.

Common Symptoms

When fault code E205 is active on your Komatsu PC200LC-7, you may experience:

• Warning light illumination on the instrument panel, often accompanied by an audible alarm
• Reduced hydraulic performance or slower cycle times as the ECM enters a protective derate mode
• Inaccurate temperature readings displayed on the monitor, showing extremely high or low values (or dashes)
• Difficulty starting in cold weather if the ECM cannot verify proper warm-up temperatures
• Intermittent code appearance that comes and goes with machine vibration or temperature changes

Potential Causes

The most common technical reasons for E205 on used PC200LC-7 excavators include:

• Failed hydraulic oil temperature sensor due to internal element degradation (common after 5,000+ operating hours)
• Damaged or corroded wiring harness between the sensor and ECM, especially at connection points near the hydraulic tank
• Loose or oxidized electrical connectors at the sensor plug or ECM harness interface
• Shorted sensor wiring caused by harness rubbing against the frame or hydraulic lines (known wear point on this model)
• ECM internal circuit failure (rare, but possible in high-hour machines with electrical system history)
• Contaminated connector pins from hydraulic oil mist or moisture intrusion in the engine compartment

How to Troubleshoot and Fix Code E205

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor on the hydraulic tank (typically mounted on the side or bottom of the tank). Inspect the sensor connector for corrosion, oil contamination, or pushed-back pins. Check the entire wiring harness from sensor to ECM for visible damage, melted insulation, or rub-through points where the harness contacts metal components. On used excavators, pay special attention to harness routing near moving parts or hot surfaces.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance. The PC200LC-7 hydraulic temperature sensor should show approximately 2,500 ohms at 20°C (68°F), decreasing as temperature rises. Compare your readings to the factory resistance-temperature chart in the service manual. Next, check circuit continuity by measuring resistance between the sensor connector pins and the corresponding ECM pins (typically less than 5 ohms). Also check for shorts to ground (should read infinite resistance).

Step 3: Sensor and Circuit Repair If the sensor resistance is out of specification or open/shorted, replace the hydraulic oil temperature sensor with a genuine Komatsu part (part number varies by serial number prefix). If wiring issues are found, repair damaged sections using heat-shrink solder connectors rated for high-temperature environments. Clean all connector pins with electrical contact cleaner and apply dielectric grease before reconnection. After repairs, clear the fault code using Komatsu diagnostic software (KOMTRAX Plus) or a compatible scan tool, then verify the repair by operating the machine through a full heat cycle.

Used Excavator Consideration: Before replacing the sensor, thoroughly inspect all electrical connections and harnesses. Many E205 codes on older PC200LC-7 machines result from corroded connectors or worn harness insulation rather than actual sensor failure, potentially saving hundreds in unnecessary parts replacement.

---

Disclaimer: This guide provides general technical information for diagnostic purposes. Always consult the official Komatsu service manual for your specific machine serial number and seek assistance from qualified heavy equipment technicians for complex electrical diagnostics and repairs.