What is Kobelco SK140LC-8 Fault Code A035?

Kobelco SK140LC-8 Fault Code A035 indicates a Hydraulic Pump Control System malfunction, specifically related to the pump flow control solenoid valve circuit. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormal voltage signal or open/short circuit in the pump control solenoid that regulates hydraulic oil flow. The hydraulic pump control system is critical for the SK140LC-8 because it directly manages swing speed, boom/arm responsiveness, and overall hydraulic performance. When this code appears, the machine typically enters a derate mode to protect the hydraulic system from damage, resulting in reduced operational efficiency that can severely impact jobsite productivity.

Common Symptoms

• Dashboard warning light illuminated (yellow hydraulic system icon or malfunction indicator)
• Noticeably sluggish hydraulic response during swing, boom, or bucket operations
• Inconsistent hydraulic power delivery, especially under heavy load conditions
• Erratic engine RPM fluctuations when engaging multiple hydraulic functions simultaneously
• Machine may enter reduced power mode with limited swing speed or lifting capacity

Potential Causes

The most common technical failures triggering A035 on used SK140LC-8 excavators include:

• Faulty pump control solenoid valve (internal coil failure or mechanical sticking from contaminated hydraulic oil)
• Damaged wiring harness between the ECM and pump solenoid, particularly at the chassis frame rail where harness bundles experience rubbing against metal brackets
• Corroded or loose electrical connectors at the solenoid valve (common in machines exposed to moisture or operating in coastal/humid environments)
• ECM internal circuit degradation (less common but possible in machines with 5,000+ operating hours)
• Contaminated hydraulic oil causing solenoid valve spool binding
• Low battery voltage or failing alternator affecting solenoid actuation voltage

How to Troubleshoot and Fix Code A035

Step 1: Visual Inspection
Begin by inspecting the pump control solenoid valve connector located on the main hydraulic pump body. Check for corrosion, bent pins, or moisture intrusion. On used excavators, this connector frequently suffers damage from hydraulic oil mist accumulation. Clean connections with electrical contact cleaner and verify physical integrity.

Step 2: Electrical Testing
Using a digital multimeter, check solenoid coil resistance at the valve connector (typical specification: 10-15 ohms for Kobelco systems). Then verify power supply voltage from the ECM with ignition on (should read 12V). Test the ground circuit continuity to chassis. Check harness for shorts by measuring resistance between solenoid wires and ground (should read infinite resistance/open circuit).

Step 3: Wiring Harness Inspection
Trace the solenoid harness from the pump to the ECM, paying special attention to routing near the counterweight pivot point and along the frame rail. Used machines often develop harness damage from rubbing at these friction points. Look for worn insulation, exposed copper wire, or heat damage.

Step 4: Solenoid Replacement or ECM Diagnosis
If electrical tests pass specification, replace the pump control solenoid valve (Kobelco part number typically begins with YN series). If the new solenoid doesn't resolve the code, connect Kobelco KOMTRAX diagnostic software to check for ECM internal faults or reprogram ECM parameters.

Used Equipment Consideration: Before replacing expensive components, always check hydraulic oil condition and filter status, as contaminated oil frequently causes solenoid valve failures in older machines.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Kobelco service manual for your specific machine serial number and seek qualified technician assistance for complex repairs involving hydraulic or electrical systems.