Komatsu PC850SE-8R Fault Code E-24: Complete Diagnostic Guide

What is Komatsu PC850SE-8R Fault Code E-24?

Fault Code E-24 on the Komatsu PC850SE-8R 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 temperature monitoring system that protects the engine from overheating damage.

The coolant temperature sensor provides critical data to the ECM, which uses this information to regulate fuel injection timing, engine speed limits, and activate warning systems. On the PC850SE-8R's high-output diesel engine, maintaining proper temperature monitoring is essential for preventing catastrophic engine damage and ensuring optimal hydraulic system performance. When this sensor circuit fails, the ECM cannot accurately assess engine thermal conditions, potentially leading to reduced machine protection and performance limitations.

Common Symptoms

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

• Engine warning light or check engine indicator illuminated on the monitor panel
• Engine derate mode engaged, limiting maximum RPM and hydraulic power output
• Erratic or frozen coolant temperature gauge readings on the display
• Cooling fan running continuously at high speed regardless of actual engine temperature
• Potential automatic engine shutdown if the ECM interprets the fault as a critical overheat condition

Potential Causes

The most common technical reasons for E-24 on used PC850SE-8R excavators include:

• Coolant temperature sensor failure due to age-related degradation or thermal cycling stress
• Damaged wiring harness near the engine block where vibration and heat cause insulation breakdown
• Corroded or loose connector pins at the sensor plug, especially on machines with high operating hours
• ECM internal circuit failure affecting the sensor input channel (less common)
• Low coolant level causing sensor exposure to air, resulting in inaccurate readings
• Shorted or open circuit in the sensor signal wire between the sensor and ECM

How to Troubleshoot and Fix Code E-24

Step 1: Visual Inspection Begin by checking actual coolant level and condition. Inspect the coolant temperature sensor (typically located on the engine block near the thermostat housing) and its wiring harness for obvious damage, corrosion, or oil contamination. On used excavators, pay special attention to harness routing where it contacts hot engine surfaces or moving components.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure resistance across the sensor terminals. Compare readings against Komatsu specifications (typically 2,000-3,000 ohms at room temperature, decreasing as temperature rises). Check for continuity in the wiring from sensor to ECM connector and verify no shorts to ground.

Step 3: Advanced Diagnostics Connect Komatsu diagnostic software (KOMTRAX or compatible scan tool) to read live sensor data and compare against actual engine temperature. Check for voltage supply at the sensor connector (typically 5V reference from ECM). If sensor and wiring test correctly but code persists, suspect ECM issues requiring dealer-level diagnostics.

For used machinery, always clean connector terminals with electrical contact cleaner and apply dielectric grease before reassembly to prevent future corrosion-related failures.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific serial number and seek qualified technician assistance for complex repairs or ECM programming.