Komatsu PC110-7 Fault Code E-20: Complete Diagnostic Guide

What is Komatsu PC110-7 Fault Code E-20?

Fault Code E-20 on the Komatsu PC110-7 indicates a malfunction in the hydraulic oil temperature sensor circuit. This code is triggered when the ECM (Engine Control Module) detects an abnormal voltage signal from the temperature sensor monitoring the hydraulic oil system.

The hydraulic oil temperature sensor is critical for the PC110-7's performance management system. It monitors oil temperature to prevent overheating, protect hydraulic components, and maintain optimal viscosity for system efficiency. When this sensor circuit fails, the machine may enter a protective derate mode or display warnings, limiting productivity and potentially causing premature wear on hydraulic pumps and motors.

Common Symptoms

When Code E-20 is active on your Komatsu PC110-7, you may experience:

• Warning light illuminated on the instrument panel (typically a hydraulic system indicator)
• Erratic temperature gauge readings or gauge stuck at maximum/minimum positions
• Reduced hydraulic performance as the ECM may limit pump output to protect the system
• Intermittent alarms that come and go, especially when operating in varying temperature conditions
• Engine derate mode activation in some cases, preventing full throttle operation

Potential Causes

For used Komatsu PC110-7 excavators, the following are the most common causes of Code E-20:

• Faulty hydraulic oil temperature sensor due to age-related degradation or thermal cycling damage
• Damaged wiring harness near the hydraulic tank, particularly where cables route close to frame members or pivot points
• Corroded or loose connectors at the sensor or ECM interface, common in machines with high operating hours
• Short circuit in the sensor wiring caused by harness rubbing against sharp edges or metal surfaces
• Failed ECM temperature input circuit, though less common than sensor or wiring issues
• Low hydraulic oil level causing sensor exposure and erratic readings

How to Troubleshoot and Fix Code E-20

Step 1: Visual Inspection Begin by inspecting the hydraulic oil temperature sensor location (typically mounted on the hydraulic tank). Check oil level first—low fluid can expose the sensor. Examine the wiring harness from the sensor to the ECM for obvious damage, chafing, or corrosion. On used excavators, pay special attention to areas where harnesses pass through bulkheads or near moving components.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance. The PC110-7's temperature sensor should typically read between 200-400 ohms at room temperature (consult your service manual for exact specifications). Next, check for continuity in the wiring from the sensor connector to the ECM. Measure voltage supply at the sensor connector with ignition on—you should see approximately 5 volts reference voltage from the ECM.

Step 3: Component Replacement and Verification If resistance readings are out of specification or the sensor shows open/short circuit conditions, replace the hydraulic oil temperature sensor with a genuine Komatsu part. Before installing, clean the mounting location and apply appropriate thread sealant. Inspect and clean all electrical connectors, applying dielectric grease to prevent future corrosion. After replacement, clear the fault code using Komatsu diagnostic software (KOMTRAX or compatible scanner) and perform a function test under normal operating temperature.

Disclaimer: This guide provides general troubleshooting information. For complex electrical issues or if you're uncomfortable performing these diagnostics, consult a certified Komatsu technician or authorized service center. Always refer to the official Komatsu PC110-7 service manual for exact specifications and safety procedures.