What is Komatsu PC200-10 Fault Code E-35?

Komatsu PC200-10 Fault Code E-35 indicates a hydraulic oil temperature sensor circuit malfunction in the hydraulic system. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects an abnormal voltage signal from the hydraulic oil temperature sensor, typically indicating an open circuit, short circuit, or sensor failure within the monitoring system.

This fault code is critical for the PC200-10's performance because the hydraulic oil temperature directly affects system efficiency, component longevity, and overall machine protection. The ECM relies on accurate temperature readings to regulate hydraulic pump output, prevent overheating damage, and maintain optimal viscosity for proper actuator response. When this sensor circuit fails, the machine may enter a protective derate mode or provide inaccurate operational data to the operator.

Common Symptoms

• Hydraulic oil temperature warning light illuminated on the monitor panel, often displaying abnormal temperature readings (extremely high or low values, or dashes)
• Reduced hydraulic power or sluggish boom/arm/bucket response as the ECM implements safety protocols
• Intermittent alarm sounds accompanied by error messages on the digital display screen
• Machine may continue operating but with limited performance capability or automatic engine speed reduction
• Monitor display freezing at a fixed temperature value regardless of actual operating conditions

Potential Causes

For used Komatsu PC200-10 excavators, E-35 typically results from age-related component degradation. The most common causes include:

• Hydraulic oil temperature sensor failure due to prolonged exposure to heat cycles and contaminated hydraulic fluid
• Damaged or corroded wiring harness connections at the sensor plug, especially where the harness routes near the hydraulic tank (a known wear point on PC200-10 models)
• Chafed wiring from rubbing against the hydraulic tank mounting brackets or frame components during machine operation
• Contamination or moisture intrusion in the sensor connector, common in machines operated in wet or corrosive environments
• ECM internal circuit issues (less common but possible in high-hour used machines)
• Poor ground connections at the sensor mounting location due to rust or paint buildup

How to Troubleshoot and Fix Code E-35

Step 1: Visual Inspection Begin with a thorough physical examination of the hydraulic oil temperature sensor located on the hydraulic oil tank. Check for obvious damage, loose connections, or oil contamination around the sensor body. Inspect the entire wiring harness from sensor to ECM, paying special attention to areas where cables contact metal surfaces or pass through chassis mounting points—these are common failure points on used equipment.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure resistance across the sensor terminals. A functional sensor typically reads between 200-3,000 ohms depending on oil temperature (consult your service manual for exact specifications). Next, check for continuity in the wiring harness from sensor connector to ECM pins. Any reading of infinite resistance indicates an open circuit requiring harness repair or replacement.

Step 3: Voltage Signal Verification With the ignition ON (engine off), measure the reference voltage at the sensor connector from the ECM—it should read approximately 5 volts. If voltage is absent, trace the circuit back toward the ECM checking for damaged wires or blown fuses. For used excavators, remove and clean all connector pins with electrical contact cleaner, as corrosion buildup frequently causes intermittent signal loss.

Step 4: Sensor Replacement and Code Clearing If the sensor tests outside specifications or shows internal failure, replace it with a genuine Komatsu hydraulic oil temperature sensor (Part #: verify with dealer for PC200-10). After replacement, use Komatsu diagnostic software (KOMTRAX) or a compatible scan tool to clear the fault code and perform a system relearn procedure. Monitor operation for at least one hour to confirm the repair.

Crucial for Used Machinery: Before replacing expensive components, thoroughly clean all electrical connectors with dielectric grease and check for harness abrasion at known wear points. Many E-35 codes on used PC200-10s result from connector corrosion rather than actual sensor failure, potentially saving hundreds in unnecessary parts costs.

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Disclaimer: This guide provides general troubleshooting information for educational purposes. Always consult the official Komatsu PC200-10 service manual and consider engaging a certified Komatsu technician for complex electrical diagnostics. Improper repairs may void warranties or create safety hazards.