What is Komatsu PC110-8M0 Fault Code CA428?

Fault Code CA428 indicates a malfunction in the hydraulic pump solenoid valve circuit within the Komatsu PC110-8M0's electronic control system. This code specifically signals that the Engine Control Module (ECM) has detected an abnormal electrical signal—either an open circuit, short circuit, or excessive resistance—in the wiring or components controlling the hydraulic pump's proportional solenoid valve.

The hydraulic pump solenoid regulates the variable displacement pump that powers all hydraulic functions on this excavator. When the ECM cannot properly communicate with or control this solenoid, it directly impacts machine performance and fuel efficiency. On the PC110-8M0, this system is critical because it manages the engine-pump matching control that balances power output with hydraulic demand, preventing engine overload while maintaining digging force.

Common Symptoms

When CA428 activates on your Komatsu PC110-8M0, operators typically experience:

• Reduced hydraulic power across all functions (boom, arm, bucket, and swing speed noticeably decrease)
• Engine warning light illuminated on the instrument panel with potential error message display
• Excessive engine RPM fluctuations or hunting, especially under load conditions
• Loss of automatic engine-pump control, causing poor fuel economy and potential engine overheating
• Machine entering derate mode or limiting maximum hydraulic flow to protect components

Potential Causes

The most common technical reasons for CA428 appearing on used PC110-8M0 excavators include:

• Damaged wiring harness between the ECM and hydraulic pump solenoid, particularly where the harness runs along the swing frame (known rub point on this model)
• Failed proportional solenoid valve on the hydraulic pump due to internal coil breakdown or contamination
• Corroded or loose connector pins at the solenoid connection or ECM plug (C-connector series)
• Voltage supply issues from the machine's main power circuit or faulty grounding points
• ECM internal fault or corrupted software calibration (less common but possible in high-hour machines)
• Hydraulic contamination causing mechanical binding of the solenoid spool, increasing electrical resistance

How to Troubleshoot and Fix Code CA428

Step 1: Visual Inspection Begin by inspecting the wiring harness from the ECM (located under the cab floor) to the hydraulic pump solenoid. On used PC110-8M0s, check where the harness passes through the swing bearing area—this is a common wear point. Look for abraded insulation, pinched wires, or evidence of previous repairs. Inspect all connector pins for corrosion, bent terminals, or moisture intrusion.

Step 2: Electrical Testing Using a digital multimeter, disconnect the solenoid connector and measure resistance across the solenoid coil terminals. The specification should be approximately 3-5 ohms (consult your service manual for exact values). Next, check for voltage supply at the harness connector with the key on—you should see approximately 12-24V DC depending on system state. Perform a continuity test from the ECM connector to the solenoid to identify any open circuits.

Step 3: Component and Software Checks If wiring tests pass, remove and bench-test the proportional solenoid valve. Check for mechanical binding by gently pushing the spool—it should move freely. For used excavators, inspect the solenoid filter screen for debris accumulation. Connect Komatsu KOMTRAX diagnostic software or an aftermarket diagnostic tool to check for additional fault codes and verify ECM output commands. Clear codes and perform an active test of the solenoid through the software to confirm ECM function.

Step 4: Replacement and Verification When replacing components on used machines, always address root causes first. Clean all electrical connectors with contact cleaner and apply dielectric grease. If replacing the harness, secure it properly to prevent future rubbing. After repairs, clear fault codes, run the machine through all hydraulic functions under load, and recheck for code reoccurrence.

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Disclaimer: This guide provides general troubleshooting information for the Komatsu PC110-8M0. Always consult the manufacturer's service manual for exact specifications and procedures. If you lack proper diagnostic tools or experience with hydraulic systems, consult a certified Komatsu technician to prevent further damage or safety hazards.