What is Kobelco SK350LC-8 Fault Code C024?

Fault Code C024 on the Kobelco SK350LC-8 excavator 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 points to either an electrical fault in the sensor wiring harness, a failed coolant temperature sensor (CTS), or an actual engine overheating condition that requires immediate attention.

The coolant temperature sensor plays a critical role in the SK350LC-8's Isuzu engine management system. It continuously monitors engine temperature and sends voltage signals to the ECM, which then adjusts fuel injection timing, idle speed, and activates cooling fan operations. When C024 triggers, the ECM cannot accurately manage engine temperature, potentially leading to reduced performance, increased fuel consumption, or catastrophic engine damage if the machine continues operating under actual overheat conditions.

Common Symptoms

• Yellow or red engine warning light illuminated on the instrument panel
• Engine derate mode activated, limiting power output and hydraulic performance
• Cooling fan running continuously at high speed, even when engine is cool
• Rough idle or hunting as the ECM struggles to maintain proper fuel delivery without accurate temperature data
• Increased white smoke from exhaust during cold starts if the ECM defaults to incorrect temperature assumptions

Potential Causes

The most common causes of C024 on used SK350LC-8 excavators include:

• Worn or corroded wiring connectors at the coolant temperature sensor, especially where the harness passes near the engine block and experiences heat cycling
• Failed coolant temperature sensor due to internal circuit breakdown (common after 5,000+ operating hours)
• Damaged wiring harness from rubbing against engine components, particularly near the fuel filter mounting area where harness routing is tight
• Corroded ECM connector pins related to the sensor circuit (pins often oxidize in humid environments)
• Low coolant level causing actual temperature spikes that trigger legitimate fault readings
• Faulty ECM (rare, but possible in machines with electrical system damage history)

How to Troubleshoot and Fix Code C024

Step 1: Visual Inspection Begin by checking the coolant level in the radiator and expansion tank. Low coolant can cause legitimate overheating. Next, locate the coolant temperature sensor (typically mounted on the engine block near the thermostat housing). Inspect the sensor connector for corrosion, pushed-back pins, or moisture intrusion—common issues on used excavators stored outdoors.

Step 2: Electrical Testing Disconnect the coolant temperature sensor connector. Using a digital multimeter, measure the sensor's resistance. At room temperature (68°F/20°C), resistance should read approximately 2,000-3,000 ohms (consult your service manual for exact specifications). If the reading is out of range or shows infinite resistance (open circuit), replace the sensor. Also check for continuity in the wiring from the sensor connector back to the ECM—look for breaks or shorts to ground.

Step 3: Harness and Connector Inspection On used SK350LC-8 machines, carefully trace the sensor harness from the engine to the main wiring loom. Check for areas where the harness may have rubbed against brackets or hot exhaust components. Inspect all intermediate connectors for green corrosion on pins. Clean connectors with electrical contact cleaner and apply dielectric grease before reconnection.

Step 4: Advanced Diagnostics If the sensor and wiring test good, connect Kobelco diagnostic software (or compatible J1939 scan tool) to read live coolant temperature data. Compare the sensor reading to actual engine temperature using an infrared thermometer on the thermostat housing. A variance greater than 10°F indicates sensor failure. Clear the code and monitor—if C024 returns immediately, suspect an ECM issue.

Critical Note for Used Equipment: Before replacing expensive components, thoroughly inspect all harness routing for age-related wear. Many C024 codes on older excavators resolve with connector cleaning and harness repositioning away from heat sources.

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Disclaimer: This guide provides general troubleshooting information. Always consult the Kobelco SK350LC-8 service manual for model-specific procedures and specifications. If you lack proper diagnostic tools or experience with heavy equipment electrical systems, consult a certified Kobelco technician to prevent misdiagnosis and unnecessary parts replacement.