Komatsu PC70-8 Fault Code E-5: Complete Diagnostic Guide

What is Komatsu PC70-8 Fault Code E-5?

Fault Code E-5 on the Komatsu PC70-8 indicates a malfunction in the hydraulic oil temperature sensor circuit or an abnormal temperature reading in the hydraulic system. This code is triggered when the Electronic Control Module (ECM) detects either an open circuit, short circuit, or an out-of-range signal from the hydraulic oil temperature sensor.

This fault is critical for the PC70-8's performance because the hydraulic system relies on proper temperature monitoring to prevent overheating, maintain optimal viscosity, and protect expensive hydraulic components. When this sensor fails, the machine may enter a protective derate mode or display inaccurate temperature readings, potentially leading to catastrophic hydraulic system damage if ignored.

Common Symptoms

When Code E-5 is active, operators typically experience:

• Warning light illuminated on the instrument panel (often a temperature or system malfunction indicator)
• Erratic or frozen hydraulic oil temperature gauge readings
• Reduced hydraulic performance or sluggish operation as the system enters protective mode
• Intermittent alarm buzzer activation, especially during warm-up or under load
• In severe cases, automatic engine shutdown to prevent hydraulic system damage

Potential Causes

The most common technical reasons for E-5 on used PC70-8 excavators include:

• Hydraulic oil temperature sensor failure due to age, heat cycling, or internal component degradation
• Damaged or corroded wiring harness connections at the sensor plug (common wear point near the hydraulic tank)
• Chafed wiring where the harness routes along the frame or near moving components
• Contaminated or corroded sensor connector pins from moisture intrusion
• Failed ECM input circuit (less common, but possible in high-hour machines)
• Actual hydraulic system overheating causing legitimate high-temperature readings

How to Troubleshoot and Fix Code E-5

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor (typically mounted on or near the hydraulic tank). Inspect the wiring harness for obvious damage, chafing, or oil contamination. On used excavators, pay special attention to connector corrosion and harness routing near pivot points.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance at ambient temperature (typically 2,000-3,000 ohms at 20°C, but consult your service manual). Check for continuity in the wiring from sensor to ECM. Test for voltage supply (usually 5V reference) at the sensor connector with ignition on.

Step 3: Component Replacement If resistance values are out of specification or the sensor shows open/short circuit, replace the hydraulic oil temperature sensor with a genuine Komatsu part. Clean all connector pins with electrical contact cleaner before reassembly. Clear the fault code using Komatsu diagnostic software (KOMTRAX or compatible scan tool) and verify proper operation.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu PC70-8 service manual and consider professional diagnostic assistance for complex electrical issues or if you're unfamiliar with hydraulic systems.