Kobelco SK460-8 Fault Code A015: Complete Diagnostic Guide

What is Kobelco SK460-8 Fault Code A015?

Fault Code A015 on the Kobelco SK460-8 excavator indicates a Main Relief Valve Solenoid Circuit Malfunction, specifically related to abnormal current or voltage detected in the hydraulic pressure control system's electrical circuit. This code triggers when the Electronic Control Module (ECM) detects an open circuit, short circuit, or improper resistance within the main relief valve solenoid wiring or the solenoid itself.

The main relief valve solenoid is critical for the SK460-8's hydraulic performance, as it regulates maximum system pressure to prevent component damage and optimize fuel efficiency. This fault directly impacts the machine's ability to maintain proper hydraulic pressure under varying load conditions, potentially compromising lifting capacity and cycle times. On used excavators, this code frequently appears due to age-related electrical degradation rather than actual solenoid failure.

Common Symptoms

When Code A015 is active, operators typically experience:

• Warning lamp illumination on the instrument cluster with reduced hydraulic performance
• Noticeable loss of digging force or sluggish boom/arm movements during heavy operations
• Inconsistent hydraulic response where the machine periodically enters a derated pressure mode
• Intermittent code appearance that may clear and return, especially during temperature changes or machine vibration
• Increased fuel consumption as the system compensates for improper pressure regulation

Potential Causes

The most common technical failures triggering A015 on used SK460-8 excavators include:

• Corroded or damaged solenoid connectors at the main relief valve mounting location (prone to moisture intrusion)
• Wiring harness chafing near the hydraulic pump area where vibration causes insulation wear against metal brackets
• Failed main relief valve solenoid coil due to thermal cycling and age (typical failure point after 8,000+ operating hours)
• Intermittent ground connection at the valve body mounting point caused by paint buildup or corrosion
• ECM power supply issues affecting multiple circuits simultaneously
• Previous repair attempts using incorrect wire gauge or improper splice connections

How to Troubleshoot and Fix Code A015

Step 1: Visual Inspection and Connector Verification Begin by locating the main relief valve solenoid on the hydraulic pump assembly. Disconnect the electrical connector and inspect for corrosion, bent pins, or moisture contamination. On used excavators, check for white/green corrosion deposits that indicate water intrusion. Clean contacts with electrical contact cleaner and apply dielectric grease before reconnection.

Step 2: Resistance and Continuity Testing Using a digital multimeter (DMM), measure solenoid coil resistance between the two connector pins. Specification is typically 10-15 ohms at room temperature (verify with Kobelco service manual). Test harness continuity from the ECM connector (Pin locations vary by serial number—consult wiring diagram) to the solenoid connector. Check for shorts to ground with one meter lead on each wire and the other on chassis ground—reading should be infinite resistance.

Step 3: Voltage Supply Verification With the key switch ON and connector attached, backprobe the connector using a DMM to verify the ECM supplies proper voltage (typically 12V reference signal). Fluctuating voltage indicates harness damage or poor ECM connection.

Step 4: Physical Harness Inspection Trace the entire wiring harness from ECM to solenoid, paying special attention to routing near the swing bearing area and pump mounting brackets where abrasion commonly occurs on used machines. Look for insulation wear, previous repair tape, or zip-tie damage points.

Step 5: Solenoid Replacement or Repair If resistance is out of specification or physical damage is evident, replace the main relief valve solenoid assembly. For used excavators, verify the valve body mounting surface is clean and provides proper ground. After replacement, clear codes using Kobelco diagnostic software and perform a pressure test to verify proper system operation.

Disclaimer: This guide provides general diagnostic procedures for experienced technicians. Always consult the official Kobelco service manual for your specific machine serial number, and consider professional diagnostic assistance if you're unfamiliar with hydraulic or electrical systems. Improper repairs can result in catastrophic hydraulic system failure or safety hazards.