What is Komatsu PC210LC-10 Fault Code CA428?

Fault Code CA428 indicates a hydraulic oil temperature sensor circuit malfunction in the Komatsu PC210LC-10 excavator. This Dash-10 model utilizes an advanced hydraulic management system that continuously monitors oil temperature to protect the machine from overheating and optimize hydraulic performance.

The CA428 code specifically triggers when the Engine Control Module (ECM) detects an abnormal voltage signal from the hydraulic oil temperature sensor—either an open circuit, short circuit, or out-of-range reading. On the PC210LC-10, this sensor is mounted in the hydraulic oil tank and sends real-time temperature data to the controller. When this sensor fails or its circuit malfunctions, the ECM cannot accurately monitor hydraulic system health, potentially leading to component damage from undetected overheating or unnecessary machine derating.

Common Symptoms

When CA428 is active on your PC210LC-10, operators typically experience:

• Warning light illumination on the instrument cluster (hydraulic temperature warning or check engine light)
• Reduced machine performance or automatic power derate to protect hydraulic components
• Inaccurate or erratic temperature gauge readings on the monitor display
• Intermittent code appearance that comes and goes during operation, especially during warm-up cycles
• Hydraulic system operating in default mode with pre-programmed temperature assumptions rather than actual readings

Potential Causes

For used Komatsu PC210LC-10 excavators, CA428 typically results from:

• Failed hydraulic oil temperature sensor due to age, heat cycling, or internal element degradation
• Damaged wiring harness between the sensor and ECM, particularly at known rub points near the hydraulic tank mounting area
• Corroded or loose connector pins at the sensor plug—common in machines operating in wet or corrosive environments
• Broken or chafed wires in the engine harness where it routes along the frame near the hydraulic tank
• ECM internal fault (rare) affecting the temperature sensor input circuit
• Poor ground connection at the sensor mounting point or chassis ground strap corrosion

How to Troubleshoot and Fix Code CA428

Step 1: Visual Inspection Begin with the hydraulic oil temperature sensor located on the hydraulic tank. Inspect the sensor connector for corrosion, oil contamination, bent pins, or moisture intrusion. On used excavators, this connector frequently suffers from vibration-induced looseness. Check the wiring harness routing from the sensor to the main engine harness for obvious damage, particularly where it passes near the swing motor or along sharp frame edges.

Step 2: Electrical Testing Disconnect the sensor and use a digital multimeter to measure sensor resistance. At room temperature (20°C/68°F), the sensor should typically read 2,000-3,000 ohms (consult your PC210LC-10 service manual for exact specifications). Test circuit continuity from the sensor connector back to the ECM using the machine's wiring diagram. Check for voltage supply at the sensor connector with the key on—you should see approximately 5 volts reference voltage from the ECM.

Step 3: Advanced Diagnostics Connect Komatsu KOMTRAX or compatible diagnostic software to read live sensor data. Monitor the temperature reading while the machine warms up—erratic jumps or frozen values indicate sensor failure. Inspect the sensor mounting area for coolant or hydraulic oil leaks that may affect readings. For used machines, check the hydraulic oil condition—contaminated oil can coat the sensor element, causing false readings.

Step 4: Component Replacement If the sensor tests faulty, replace it with a genuine Komatsu hydraulic temperature sensor (part number specific to PC210LC-10). When installing, apply dielectric grease to connector pins to prevent future corrosion. If wiring is damaged, repair using heat-shrink solder connections rather than crimp connectors to ensure durability in the harsh excavator environment. Clear the fault code using diagnostic software and verify proper operation through a complete heat cycle.

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Disclaimer: This guide provides general troubleshooting information for the Komatsu PC210LC-10. Always consult the official Komatsu service manual for your specific machine serial number and consider professional diagnostic assistance for complex electrical issues. Improper repairs may void warranties or create safety hazards.