What is Komatsu PC210-8 Fault Code CA428?

Fault Code CA428 indicates a malfunction in the hydraulic pump solenoid valve circuit, specifically detecting an abnormal electrical signal or open/short circuit in the pump control system. This diagnostic trouble code (DTC) is generated by the engine control module (ECM) when it detects voltage irregularities in the proportional solenoid valve that regulates main hydraulic pump displacement on the Komatsu PC210-8 excavator.

This code directly affects the variable displacement piston pump control system, which is critical for matching hydraulic flow to operational demands. The PC210-8 uses an electronically-controlled pump system that optimizes fuel efficiency and hydraulic performance. When CA428 triggers, the ECM may enter a failsafe mode, limiting pump output to protect the hydraulic system from erratic pressure conditions that could damage components or create unsafe operating conditions.

Common Symptoms

• Reduced hydraulic power across all functions, with noticeably slower boom, arm, and bucket movements
• Illuminated warning lamp on the instrument cluster, often accompanied by an audible alarm
• Engine derating or automatic reduction in RPM when hydraulic functions are engaged
• Erratic pump response where hydraulic pressure surges or drops unpredictably during operation
• Error code display on the monitor panel showing CA428 specifically

Potential Causes

The most common causes for CA428 on used PC210-8 excavators include:

• Worn or damaged solenoid valve on the main hydraulic pump (common failure point after 6,000+ operating hours)
• Corroded or loose electrical connectors at the pump solenoid harness—a known weak point where the harness passes near the pump mounting bracket
• Chafed wiring in the engine compartment where harnesses rub against frame members or hydraulic lines
• Failed ECM internal driver circuit for the solenoid valve output
• Contaminated hydraulic oil causing solenoid valve sticking or internal coil failure
• Voltage supply issues from the main power harness or poor grounding at the pump assembly

How to Troubleshoot and Fix Code CA428

Step 1: Connect Diagnostic Software Use Komatsu KOMTRAX or compatible diagnostic software to confirm CA428 is active and check for additional stored codes. Document freeze frame data showing operating conditions when the fault occurred.

Step 2: Inspect Wiring and Connectors Visually examine the pump solenoid harness from the ECM to the hydraulic pump. On used excavators, pay special attention to harness routing near the pump mounting area where vibration causes wire fatigue. Check for green corrosion on connector pins—clean with electrical contact cleaner and apply dielectric grease.

Step 3: Test Solenoid Valve Resistance Disconnect the solenoid connector and measure coil resistance with a multimeter. Specification is typically 3-7 ohms at 20°C. Readings outside this range indicate solenoid replacement is necessary.

Step 4: Check Voltage Supply With ignition on and connector attached, backprobe the solenoid harness to verify 12V supply voltage from the ECM. No voltage indicates a wiring fault or ECM driver failure.

Step 5: Perform Solenoid Functional Test If resistance and voltage are correct, the solenoid may be mechanically stuck. Remove the valve assembly and check for contamination or scoring on the spool. Replace hydraulic oil filters if contamination is evident.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific machine serial number and consider professional diagnosis for complex electrical issues or ECM replacement procedures.