Komatsu PC70-8 Fault Code E-19: Complete Diagnostic Guide

What is Komatsu PC70-8 Fault Code E-19?

Fault Code E-19 on the Komatsu PC70-8 indicates a malfunction in the hydraulic oil temperature sensor circuit. This code triggers when the Engine Control Module (ECM) detects an abnormal voltage signal from the temperature sensor monitoring the hydraulic oil system.

The hydraulic oil temperature sensor is critical for the PC70-8's performance management system. It monitors oil viscosity conditions and prevents overheating damage to hydraulic components. When this sensor fails or sends erratic signals, the ECM cannot properly regulate system performance, potentially leading to reduced efficiency or component damage. This is particularly important in the PC70-8's compact hydraulic system, where temperature control directly affects seal integrity and pump longevity.

Common Symptoms

When Code E-19 is active, operators typically experience:

• Warning light illuminated on the instrument panel (typically a hydraulic system indicator)
• Erratic hydraulic oil temperature gauge readings or gauge stuck at minimum/maximum
• Reduced hydraulic system performance or sluggish operation during cold starts
• ECM may activate derate mode, limiting engine RPM to protect hydraulic components
• Intermittent code activation that correlates with machine vibration or temperature changes

Potential Causes

The most common technical causes for E-19 on used PC70-8 excavators include:

• Temperature sensor failure due to age-related degradation or thermal cycling stress
• Damaged or corroded wiring harness connections at the sensor plug (common wear point near hydraulic tank)
• Broken or frayed wires in the harness routing along the frame rails where rubbing occurs
• Contaminated sensor tip from hydraulic oil degradation or metallic debris
• ECM internal circuit fault (rare, but possible in high-hour machines)
• Poor ground connection at sensor mounting point due to corrosion

How to Troubleshoot and Fix Code E-19

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor (typically mounted on the hydraulic tank). Inspect the sensor connector for corrosion, oil contamination, or bent pins. Check the wiring harness routing for obvious damage, particularly where it passes near moving components or sharp edges.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across its terminals. Compare readings against Komatsu specifications (typically 200-400 ohms at 20°C). Check voltage supply at the harness connector with ignition on (should read approximately 5V reference voltage). Test continuity from sensor connector back to the ECM to identify wire breaks.

Step 3: Component Replacement and Verification If sensor resistance is out of specification or wiring shows damage, replace the faulty component. For used excavators, always clean connector terminals with electrical contact cleaner and apply dielectric grease before reconnection. Clear the code using Komatsu diagnostic software (KOMTRAX or compatible scan tool) and monitor for recurrence during a full operating cycle.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number and consider professional technician assistance for complex electrical diagnostics.