Komatsu PC110-7 Fault Code E-8: Technical Guide

What is Komatsu PC110-7 Fault Code E-8?

Fault Code E-8 on the Komatsu PC110-7 indicates a hydraulic oil temperature sensor circuit malfunction or abnormal temperature reading in the hydraulic system. This code is triggered when the Engine Control Module (ECM) detects an irregular signal from the hydraulic oil temperature sensor, which may indicate an open circuit, short circuit, or actual overheating condition.

The hydraulic oil temperature sensor is critical for the PC110-7's performance because it monitors the operating temperature of the hydraulic system. When hydraulic oil exceeds safe operating temperatures (typically above 95-100°C), component wear accelerates dramatically, seal degradation occurs, and system efficiency drops. This sensor provides vital data that prevents catastrophic hydraulic pump failure and extends component life.

Common Symptoms

When Code E-8 is active on your Komatsu PC110-7, operators typically experience:

• Warning light illuminated on the instrument panel, often accompanied by an audible alarm
• Reduced hydraulic performance including slower cycle times and decreased lifting capacity
• Erratic temperature gauge readings or gauge showing maximum temperature immediately upon startup
• Intermittent code appearance, especially during cold starts or after extended operation
• Derated engine power in some cases, as the ECM enters protective mode to prevent damage

Potential Causes

Several issues commonly trigger E-8 on used PC110-7 excavators:

• Faulty hydraulic oil temperature sensor due to internal resistance drift or element failure (common after 5,000+ operating hours)
• Damaged wiring harness at the sensor connector, particularly where the harness routes near the hydraulic tank and experiences vibration
• Corroded or loose electrical connections at the sensor plug or ECM terminals
• Actual hydraulic system overheating caused by low oil levels, clogged hydraulic cooler fins, or malfunctioning cooling fan
• ECM calibration issues or software glitches requiring recalibration
• Broken or chafed wires at known rub points near the swing bearing or along the boom base

How to Troubleshoot and Fix Code E-8

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor (typically mounted on the hydraulic tank). Inspect the wiring harness for visible damage, particularly where it contacts the frame or passes through grommets. On used excavators, check for oil contamination on connectors, which indicates seal failure. Clean all connectors with electrical contact cleaner and examine for corrosion or bent pins.

Step 2: Sensor and Circuit Testing Using a digital multimeter, disconnect the sensor and measure its resistance at various temperatures. At 25°C (room temperature), resistance should typically read 2,000-3,000 ohms (consult your service manual for exact specifications). Check for continuity in the wiring from sensor to ECM—resistance should be less than 5 ohms. Test for short circuits to ground by measuring resistance between each wire and chassis ground (should read infinite/OL).

Step 3: Live Data Analysis and Component Replacement Connect Komatsu diagnostic software (KOMTRAX or compatible scan tool) to read live hydraulic oil temperature data. Compare the displayed temperature with actual oil temperature measured with an infrared thermometer. If readings differ by more than 10°C, replace the sensor. Before replacing parts on used machines, verify the hydraulic cooler isn't blocked and oil level is correct—actual overheating often mimics sensor failure. If sensor and wiring test properly but the code persists, ECM recalibration or replacement may be necessary.

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Disclaimer: This guide provides general diagnostic information for the Komatsu PC110-7. Always consult the manufacturer's service manual and consider professional diagnostic assistance for complex electrical issues. Improper troubleshooting can cause additional damage or safety hazards.