Komatsu PC110-7 Fault Code E-31: Technical Guide

What is Komatsu PC110-7 Fault Code E-31?

Fault Code E-31 on the Komatsu PC110-7 indicates a hydraulic oil temperature sensor circuit malfunction or an abnormal temperature reading in the hydraulic system. This code is triggered when the Electronic Control Module (ECM) detects voltage signals outside the normal operating range from the hydraulic oil temperature sensor, typically located in the main hydraulic tank or control valve assembly.

This fault is critical for the PC110-7 because the hydraulic system relies on proper temperature monitoring to prevent oil degradation, seal damage, and catastrophic hydraulic component failure. When the ECM cannot accurately read hydraulic temperatures, it may limit machine performance or activate protective derate modes to prevent expensive repairs.

Common Symptoms

When Code E-31 is active on your PC110-7, operators typically experience:

• Warning light illumination on the instrument panel, often accompanied by a temperature warning icon
• Reduced hydraulic response or slower cycle times as the system enters a protective mode
• Intermittent or constant error code display on the monitor panel
• Unusual hydraulic system behavior, such as the machine thinking oil is too hot when it's actually cold, or vice versa
• Potential automatic shutdown or reduced engine RPM in severe cases to protect hydraulic components

Potential Causes

The E-31 code on used PC110-7 excavators commonly results from:

• Failed hydraulic oil temperature sensor due to internal resistance drift or element degradation (common after 5,000+ operating hours)
• Damaged or corroded wiring harness at connector points, especially near the hydraulic tank where vibration and heat cycles cause wear
• Broken or frayed sensor wires at known rub points along the main boom base or near the swing motor area
• Corroded connector pins at the sensor plug or ECM interface due to moisture infiltration in older machines
• ECM software issues or internal controller faults (less common but possible in high-hour machines)
• Poor electrical ground connections at the sensor mounting location or chassis ground points

How to Troubleshoot and Fix Code E-31

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor on the hydraulic tank (typically on the right side near the control valve). Inspect the sensor connector for corrosion, oil contamination, or damaged pins. Check the entire wiring harness from sensor to ECM for visible damage, especially at flex points and areas where the harness contacts frame members. On used excavators, pay special attention to harness routing near moving components.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to measure sensor resistance. At room temperature (20°C/68°F), the sensor should typically read between 2,000-3,000 ohms (consult your PC110-7 service manual for exact specifications). Test the wiring harness for continuity from the sensor connector to the ECM pins and check for shorts to ground. Measure voltage supply at the sensor connector with the key on—you should see approximately 5 volts reference voltage from the ECM.

Step 3: Advanced Diagnostics If wiring and sensor resistance check normal, use Komatsu diagnostic software (KOMTRAX Plus) or a compatible scan tool to monitor live sensor data. Compare the temperature reading to an infrared thermometer measurement of actual hydraulic oil temperature. A variance greater than 10°C indicates sensor failure. Check ECM ground connections at the controller mounting location—corroded grounds frequently cause voltage signal issues on used machines.

Step 4: Component Replacement Replace the hydraulic oil temperature sensor if resistance values are out of specification or if live data shows inaccurate readings. When installing a new sensor, apply dielectric grease to connector pins to prevent future corrosion. If the sensor tests properly, inspect the ECM harness connector and repair any damaged wires using OEM-specification wire and heat-shrink connections. Always clear codes after repairs and perform a test cycle to verify proper operation.

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Disclaimer: This guide provides general troubleshooting information for the Komatsu PC110-7 fault code E-31. Hydraulic and electrical system repairs should be performed by qualified technicians with proper training and tools. Always consult the official Komatsu service manual for your specific machine serial number and follow all safety procedures. Improper diagnostics or repairs may result in equipment damage or personal injury.