What is Komatsu PC210LC-10 Fault Code E-31?

Fault Code E-31 on the Komatsu PC210LC-10 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, typically indicating an open circuit, short circuit, or sensor failure.

The hydraulic oil temperature sensor plays a critical role in the PC210LC-10's operational safety and efficiency. This sensor monitors the temperature of the hydraulic fluid in real-time, allowing the ECM to prevent overheating conditions that could damage hydraulic pumps, control valves, and cylinder seals. When the sensor circuit malfunctions, the machine may enter a protective derate mode or display warning messages, significantly impacting productivity on job sites.

Common Symptoms

When Code E-31 is active on your Komatsu PC210LC-10, operators typically experience:

• Hydraulic oil temperature warning light illuminated on the monitor panel
• Reduced hydraulic system performance or sluggish operation, especially during startup
• Error message displayed on the multi-function monitor indicating hydraulic temperature sensor failure
• Machine may enter limited operation mode, restricting swing speed or boom/arm movements
• Inaccurate or frozen temperature readings on the instrument cluster (often showing -40°C or maximum readings)

Potential Causes

Several factors commonly trigger Code E-31 on used PC210LC-10 excavators:

• Damaged or corroded wiring harness between the sensor and ECM, particularly at flex points near the hydraulic tank mounting area
• Failed hydraulic oil temperature sensor due to age, contamination, or thermal cycling stress
• Loose or corroded electrical connectors at the sensor or ECM connection points—common in machines operated in wet or marine environments
• Chafed wiring rubbing against the hydraulic tank or frame members, causing intermittent shorts
• ECM internal fault (less common) affecting the sensor input circuit
• Water intrusion into the sensor connector, especially on older machines with deteriorated sealing boots

How to Troubleshoot and Fix Code E-31

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor, typically mounted on the hydraulic oil tank. Inspect the sensor body and electrical connector for physical damage, corrosion, or oil contamination. Check the wiring harness from the sensor to the ECM for signs of chafing, particularly where it routes along the tank or frame. On used excavators, pay special attention to areas where the harness may have contacted moving components over thousands of operating hours.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure the resistance across the sensor terminals. For the PC210LC-10, the sensor should typically read between 200-300 ohms at 20°C (consult your service manual for exact specifications). If the reading shows infinite resistance (open circuit) or zero ohms (short circuit), the sensor has failed and requires replacement.

Step 3: Circuit Verification With the sensor disconnected, check for continuity in the wiring harness from the sensor connector back to the ECM. Look for shorts to ground by measuring resistance between each wire and the machine chassis—readings should show infinite resistance. Test the supply voltage from the ECM (typically 5 volts reference) with the ignition on. If voltage is absent or incorrect, the issue may lie within the ECM or a damaged harness.

Step 4: Connector and Harness Repair Clean all electrical connectors using electrical contact cleaner and inspect for bent pins or corrosion. Apply dielectric grease to protect against future moisture intrusion. If wiring damage is found, repair using heat-shrink butt connectors and proper gauge wire, ensuring routing avoids friction points.

Step 5: Component Replacement and Verification Replace the sensor using a genuine Komatsu part or high-quality aftermarket equivalent. After installation, clear the fault code using Komatsu diagnostic software (KOMTRAX Plus or compatible scan tool) and operate the machine through a complete warm-up cycle. Monitor the hydraulic temperature readings to confirm accurate operation and verify the code does not return.

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Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Komatsu service manual for your specific machine serial number and follow proper safety procedures. For complex electrical issues or if you're uncomfortable performing these diagnostics, seek assistance from a certified Komatsu technician or qualified heavy equipment repair facility.