Komatsu PC200-10 Fault Code E-6: Complete Diagnostic Guide

What is Komatsu PC200-10 Fault Code E-6?

Fault Code E-6 on the Komatsu PC200-10 excavator indicates a Hydraulic Oil Temperature Sensor Circuit Malfunction. This code triggers when the Electronic Control Module (ECM) detects abnormal voltage readings from the hydraulic oil temperature sensor, typically outside the normal operating range of 0.5-4.5 volts.

The hydraulic oil temperature sensor continuously monitors fluid temperature in the hydraulic system to prevent overheating and optimize pump performance. For the PC200-10, maintaining proper hydraulic oil temperature (typically 50-80°C during operation) is critical for preventing accelerated component wear, maintaining viscosity, and protecting expensive hydraulic pumps and motors. When this sensor circuit fails, the ECM cannot properly manage system cooling or implement protective derating protocols.

Common Symptoms

• Yellow warning light illuminated on the monitor panel with "E-6" displayed on the multi-information screen
• Hydraulic system overheating without operator awareness, potentially causing pump damage
• Reduced hydraulic response as the ECM enters a default safe mode with limited flow
• Cooling fan running continuously at high speed regardless of actual oil temperature
• Intermittent code triggering during machine operation, especially when traveling over rough terrain

Potential Causes

Sensor-Related Issues:

• Failed hydraulic oil temperature sensor (common after 5,000-8,000 operating hours on used machines)
• Corroded or moisture-damaged sensor connector pins in the hydraulic tank area

Wiring Problems:

• Harness chafing at the routing point near the hydraulic tank mounting bracket (known wear point on PC200-10 models)
• Broken wires inside the insulation jacket due to vibration fatigue
• Ground circuit failure at chassis connection points

ECM/System Issues:

• Faulty ECM input circuit (rare but possible on high-hour used excavators)
• Contaminated hydraulic oil causing sensor element coating and false readings

How to Troubleshoot and Fix Code E-6

Step 1: Visual Inspection Locate the hydraulic oil temperature sensor mounted on the hydraulic tank (typically on the left side of the PC200-10). Inspect the wiring harness from sensor to ECM for obvious damage, particularly where the harness passes over the tank mounting bracket. Check connector for corrosion, pushed-back pins, or oil contamination. On used excavators, this routing point commonly shows harness wear.

Step 2: Electrical Testing Disconnect the sensor connector. Using a digital multimeter, measure sensor resistance with oil cold (approximately 2,000-3,000 ohms at 20°C). Check supply voltage at the harness connector with ignition on—should read approximately 5 volts. Verify ground continuity (less than 1 ohm resistance to chassis ground). Compare readings against Komatsu specifications in the service manual.

Step 3: Signal Testing Reconnect the sensor and backprobe the connector. Start the engine and monitor voltage while warming up—voltage should gradually decrease from approximately 3.5V (cold) to 1.5V (warm). Erratic voltage swings indicate a failing sensor or poor connection.

Step 4: Component Replacement If sensor resistance is out of specification or voltage signal is erratic, replace the hydraulic oil temperature sensor (Komatsu part number 7861-93-4131 or equivalent). For used machines, always replace the connector pigtail simultaneously if corrosion is present. After replacement, clear codes using Komatsu KOMTRAX diagnostic software and perform a warm-up cycle to verify repair.

Used Equipment Consideration: Before replacing the sensor, thoroughly clean the hydraulic tank breather and check oil condition. Contaminated oil can coat sensor elements. On high-hour PC200-10s, inspect all harness mounting clips and add additional protection wrap at known chafe points.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu PC200-10 service manual and follow proper safety procedures. For complex electrical diagnostics or if you're uncertain, contact a certified Komatsu technician or authorized service center.