Komatsu PC750-7 Fault Code E-24: Complete Diagnostic Guide

What is Komatsu PC750-7 Fault Code E-24?

Fault Code E-24 on the Komatsu PC750-7 indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading detected by the Engine Control Module (ECM). This code specifically relates to the coolant temperature sensor sending irregular voltage signals outside the manufacturer's specified parameters, typically between 0.5-4.5 volts.

This fault is critical for the PC750-7's performance because the ECM relies on accurate coolant temperature data to optimize fuel injection timing, control engine speed, and prevent overheating damage. When E-24 triggers, the system may enter a protective derate mode to prevent catastrophic engine failure, significantly impacting productivity on job sites.

Common Symptoms

When Code E-24 is active, operators typically experience:

• Warning light illumination on the instrument cluster, often accompanied by an audible alarm
• Engine derate or reduced power output, limiting machine performance under load
• Hard starting conditions, especially during cold weather operation
• Erratic temperature gauge readings that fluctuate abnormally or read maximum/minimum constantly
• Increased fuel consumption due to improper fuel mapping from incorrect temperature data

Potential Causes

The most common technical causes for E-24 on used PC750-7 excavators include:

• Coolant temperature sensor failure due to internal element degradation (common after 8,000+ operating hours)
• Corroded or loose connector pins at the sensor harness connection point
• Damaged wiring harness from rubbing against engine components, particularly near the thermostat housing area
• ECM internal fault or corrupted calibration data (less common but possible in high-hour machines)
• Contaminated coolant causing sensor element coating and false readings
• Poor ground connections at the sensor or ECM mounting points

How to Troubleshoot and Fix Code E-24

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located near the thermostat housing. Check for physical damage, coolant leaks, or corrosion on the connector terminals. On used excavators, examine the wiring harness for chafing points where it contacts the engine block or brackets.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across its terminals. At 68°F (20°C), resistance should read approximately 2,000-3,000 ohms (consult your service manual for exact specifications). Test harness continuity from sensor connector to ECM pins, checking for opens or shorts to ground.

Step 3: Live Data Analysis Connect Komatsu diagnostic software (KOMTRAX or compatible scan tool) to monitor real-time sensor voltage. Compare readings against actual coolant temperature using an infrared thermometer. Voltage should decrease smoothly as temperature rises. Erratic jumps indicate sensor or wiring issues.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu part (Part #6732-81-3110 or equivalent). For used machines, always apply dielectric grease to connector pins to prevent future corrosion. Clear codes and perform a test cycle under load.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu PC750-7 service manual and consider professional technician assistance for complex electrical diagnostics or if you're unfamiliar with high-voltage systems.