What is Komatsu PC110-7 Fault Code E-5?

Komatsu PC110-7 Fault Code E-5 indicates a malfunction in the hydraulic oil temperature sensor circuit. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormal voltage signal from the hydraulic oil temperature sensor, typically caused by an open circuit, short circuit, or sensor failure.

The hydraulic oil temperature sensor plays a critical role in the PC110-7's operational safety and efficiency. It monitors the hydraulic fluid temperature and sends real-time data to the ECM, which uses this information to prevent overheating, optimize hydraulic pump performance, and protect internal components. When this sensor circuit fails, the machine cannot accurately monitor hydraulic temperatures, potentially leading to severe damage to pumps, valves, and seals—especially critical in used excavators where thermal stress accumulates over years of operation.

Common Symptoms

When Fault Code E-5 is active on your Komatsu PC110-7, you may experience:

• Warning light illumination on the instrument panel indicating a hydraulic system fault
• Erratic hydraulic performance with inconsistent boom, arm, or bucket speeds
• Machine derate mode where engine power is automatically reduced to protect hydraulic components
• Inaccurate or frozen temperature gauge readings on the operator display
• Increased hydraulic noise or sluggish response during cold starts or extended operation

Potential Causes

Several technical factors commonly trigger E-5 on used PC110-7 excavators:

• Faulty hydraulic oil temperature sensor due to internal element degradation or contamination exposure
• Damaged wiring harness between the sensor and ECM, particularly at known rub points near the hydraulic tank mounting bracket
• Corroded or loose electrical connectors at the sensor plug, especially in machines exposed to water or mud
• Short circuit to ground caused by chafed insulation along the chassis frame routing path
• ECM internal circuit failure (rare, but possible in high-hour used machines)
• Hydraulic fluid contamination causing sensor element coating or failure

How to Troubleshoot and Fix Code E-5

Step 1: Visual Inspection Begin with a thorough physical examination of the hydraulic oil temperature sensor located on the hydraulic tank. Check for visible damage, oil leaks around the sensor body, and corrosion on the electrical connector. Inspect the wiring harness from the sensor to the ECM, paying special attention to areas where the harness contacts metal surfaces or passes through bulkheads—common wear points on used excavators.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure resistance across the sensor terminals. A typical operational sensor should read between 200-600 ohms at room temperature (consult your service manual for exact specifications). Next, check for continuity in the wiring harness from sensor to ECM. Measure voltage supply at the sensor connector with ignition on—you should see approximately 5 volts reference voltage from the ECM.

Step 3: Connector and Ground Verification Clean all electrical connectors with contact cleaner and inspect for bent pins or moisture infiltration. Verify the ground circuit integrity by checking resistance between the sensor ground wire and chassis ground (should be less than 1 ohm). On used machines, corrosion buildup at ground points is a frequent culprit.

Step 4: Component Replacement If testing confirms sensor failure, replace the hydraulic oil temperature sensor with a genuine Komatsu or OEM-equivalent part. After installation, clear the fault code using Komatsu diagnostic software (KOMATSU Diagnostic eXplorer or compatible scan tool) and perform a verification test cycle. Monitor hydraulic temperatures during operation to confirm proper readings.

Important for Used Excavators: Before replacing expensive components, thoroughly inspect all harness routing for friction wear, check all splice points for integrity, and verify that previous repairs weren't performed with incorrect wire gauges or poor crimping techniques.

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Disclaimer: This guide provides general diagnostic information for Komatsu PC110-7 Fault Code E-5. Always consult the manufacturer's official service manual and consider professional assistance from certified Komatsu technicians for complex electrical diagnostics or if you're uncertain about any repair procedures.