What is Kobelco SK135SRLC-2 Fault Code A225?

Fault Code A225 on the Kobelco SK135SRLC-2 indicates a hydraulic pump flow control solenoid valve malfunction or electrical circuit abnormality. This code is triggered when the machine's Electronic Control Unit (ECU) detects improper voltage signals, resistance values, or response times from the pump flow control solenoid, which regulates hydraulic oil flow to match operational demands.

This code is particularly critical for the SK135SRLC-2 because the proportional flow control system directly affects digging force, swing speed, and overall hydraulic performance. When this solenoid malfunctions, the excavator cannot properly modulate pump output, leading to reduced efficiency, overheating, and potential damage to the main hydraulic pump. In used machines, this fault commonly appears due to electrical connector corrosion or mechanical wear on the solenoid valve itself.

Common Symptoms

• Reduced hydraulic power across all functions (boom, arm, bucket, and swing operations feel sluggish)
• Warning light illumination on the instrument cluster with simultaneous fault code display
• Inconsistent engine RPM response when operating hydraulics under load
• Hydraulic oil overheating due to improper flow regulation and excessive pressure relief valve cycling
• Intermittent loss of hydraulic function that may temporarily resolve after restarting the machine

Potential Causes

The most likely technical causes for Code A225 on used SK135SRLC-2 excavators include:

• Solenoid valve coil failure due to internal short circuit or open winding (common after 5,000+ operating hours)
• Corroded or loose electrical connectors at the pump-mounted solenoid, especially machines operated in wet or coastal environments
• Damaged wiring harness along the main chassis routing path where cables rub against frame members near the hydraulic tank
• ECU voltage supply issues from failing alternator or battery connections affecting solenoid control signal
• Contaminated hydraulic oil causing mechanical sticking of the solenoid spool valve
• Faulty ECU output driver circuit (less common but possible in high-hour machines)

How to Troubleshoot and Fix Code A225

Step 1: Visual Inspection and Connector Check Begin by locating the pump flow control solenoid on the main hydraulic pump. Disconnect the electrical connector and inspect for corrosion, bent pins, or moisture intrusion. Clean contacts with electrical cleaner and apply dielectric grease. On used excavators, check the wiring harness routing from the solenoid to the ECU for abrasion points, especially near mounting brackets.

Step 2: Electrical Testing with Multimeter With the connector disconnected and ignition off, measure the solenoid coil resistance across the two terminals. Typical specifications for Kobelco solenoids range from 10-30 ohms (consult service manual for exact values). Then check for voltage supply at the harness connector with ignition on—should read approximately 12V DC. Any significant deviation indicates wiring faults or ECU issues.

Step 3: Functional Testing and Component Replacement Using Kobelco diagnostic software (KPSS or compatible scan tool), command the solenoid to actuate while monitoring system response. If voltage and resistance are correct but the solenoid doesn't respond, replace the solenoid valve assembly. For used machines, also replace the connector pigtail if corrosion is present, as intermittent connections will cause recurring codes.

Step 4: Hydraulic System Verification After electrical repairs, check hydraulic oil quality and filter condition. Contaminated oil can cause mechanical binding even with proper electrical function. Perform a complete system pressure test to verify proper pump output modulation.

---

Disclaimer: This guide provides general troubleshooting information. Always consult the official Kobelco service manual for your specific serial number and consider professional diagnosis for complex electrical or hydraulic issues. Improper repairs may void warranties or cause equipment damage.