What is Komatsu PC200LC-7 Fault Code E206?

Fault Code E206 on the Komatsu PC200LC-7 indicates a malfunction in the hydraulic oil temperature sensor circuit. This diagnostic trouble code (DTC) is triggered when the engine control module (ECM) detects an abnormal voltage signal from the temperature sensor monitoring the hydraulic oil in the main hydraulic system.

The hydraulic oil temperature sensor plays a critical role in protecting the PC200LC-7's hydraulic system from overheating damage. This sensor continuously monitors hydraulic fluid temperature and sends voltage signals to the ECM. When temperatures exceed safe operating parameters or the sensor circuit fails, the ECM logs E206 and may activate protection modes. For used excavators, this code often appears due to sensor degradation, corroded connectors, or wiring harness damage from years of vibration and exposure to contaminants.

Common Symptoms

• Warning light illuminated on the instrument cluster, often accompanied by a specific hydraulic system alarm
• Reduced hydraulic performance or sluggish boom/arm/bucket response as the ECM limits pump output
• Erratic temperature gauge readings showing unusually high, low, or fluctuating hydraulic oil temperatures
• Machine derate mode where engine power is automatically reduced to protect hydraulic components
• Stored fault code visible when using Komatsu diagnostic software (KOMTRAX or PC-based tools)

Potential Causes

The most common causes of E206 on used PC200LC-7 excavators include:

• Failed hydraulic oil temperature sensor due to age-related degradation or internal short/open circuit
• Damaged wiring harness between the sensor and ECM, particularly at known rub points near the hydraulic tank mounting area
• Corroded or loose electrical connectors at the sensor plug, often caused by hydraulic oil contamination or moisture intrusion
• ECM internal fault affecting the sensor input circuit (rare but possible on high-hour machines)
• Intermittent connection issues caused by vibration loosening terminals over years of operation

How to Troubleshoot and Fix Code E206

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor on the hydraulic oil tank (typically on the side or top of the reservoir). Inspect the sensor connector for oil contamination, corrosion, or damaged pins. Check the wiring harness from the sensor to the ECM for chafing, cuts, or wear points where the harness contacts the frame—this is especially critical on used excavators with 5,000+ operating hours.

Step 2: Electrical Testing Disconnect the sensor and use a digital multimeter to measure resistance across the sensor terminals. For the PC200LC-7, typical resistance values range from 200-400 ohms at room temperature (consult your service manual for exact specifications). Test the harness continuity by checking for open circuits between the sensor connector and ECM pins. Measure voltage supply from the ECM (typically 5V reference voltage) with the key on, engine off.

Step 3: Component Replacement and Verification If resistance values are out of specification or the sensor shows internal failure, replace the hydraulic oil temperature sensor with a genuine Komatsu part (Part #7861-93-3320 or equivalent). Before installing, clean the mounting threads and apply anti-seize compound. After replacement, clear codes using Komatsu diagnostic software and perform a function test by monitoring live sensor data during warm-up. For used machines, always inspect and clean all electrical connections even when replacing sensors, as corrosion often causes repeat failures.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu PC200LC-7 service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs may cause further damage or safety hazards.