What is Komatsu PC240LC-10 Fault Code E-24?

Fault Code E-24 on the Komatsu PC240LC-10 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 signals that the ECM has detected either an electrical fault in the sensor's wiring harness, a failed coolant temperature sensor, or actual engine overheating beyond safe operating parameters.

This fault is critical for the PC240LC-10 because the ECM relies on accurate coolant temperature data to regulate fuel injection timing, throttle response, and activate cooling system protocols. When E-24 triggers, the machine may enter a derate mode to prevent catastrophic engine damage from overheating or operate inefficiently due to incorrect temperature compensation.

Common Symptoms

When Code E-24 is active on your Komatsu PC240LC-10, operators typically experience:

• Engine warning light illuminated on the monitor panel, often accompanied by an audible alarm
• Reduced engine power or automatic throttle limitation (derate mode) as a protective measure
• Erratic temperature gauge readings that fluctuate wildly or show maximum temperature immediately upon startup
• Difficulty starting in cold conditions due to incorrect cold-start fuel enrichment
• Poor fuel economy and black exhaust smoke from improper air-fuel mixture calculations

Potential Causes

The most common technical causes for E-24 on used PC240LC-10 excavators include:

• Coolant temperature sensor failure due to thermal cycling fatigue or internal element degradation (common after 6,000+ hours)
• Damaged wiring harness near the sensor connector, particularly where the harness passes near the exhaust manifold or engine mounts—a known wear point on this model
• Corroded or loose connector pins at the sensor or ECM side, especially in machines operating in marine or high-humidity environments
• Low coolant level causing actual overheating and triggering legitimate temperature warnings
• Failed ECM (rare, but possible in high-hour used machines with previous electrical system issues)

How to Troubleshoot and Fix Code E-24

Step 1: Visual Inspection Begin by checking the coolant level in the radiator and overflow tank. On used excavators, inspect the sensor connector located on the thermostat housing for corrosion, bent pins, or coolant seepage. Examine the wiring harness from sensor to ECM for abrasion, particularly where it contacts metal surfaces or heat sources.

Step 2: Electrical Testing Using a digital multimeter, disconnect the coolant temperature sensor and measure its resistance. At 68°F (20°C), resistance should read approximately 2,500 ohms (consult your service manual for exact specifications). Check for open circuits or short to ground in the harness by measuring continuity between the sensor connector and ECM pins with the harness disconnected.

Step 3: Component Replacement If resistance values are out of specification or the sensor shows physical damage, replace the coolant temperature sensor (Komatsu part number varies by engine serial—verify before ordering). For used excavators, always apply dielectric grease to connector pins to prevent future corrosion. Clear the fault code using Komatsu diagnostic software (KTSS) or a compatible scan tool and perform a test cycle.

Crucial for Used Machines: Before replacing expensive components, thoroughly inspect all harness routing for wear from engine vibration—a zip-tie repair preventing harness movement often resolves intermittent E-24 codes on older PC240LC-10 models.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific machine serial number and consider professional diagnostic assistance for complex electrical issues or if you lack proper testing equipment.