What is Hitachi ZX690LCH-5A Fault Code 14105-2?

Fault Code 14105-2 indicates a Main Pump Solenoid Valve (PC-EPC) Circuit Low Voltage condition in the Hitachi ZX690LCH-5A excavator's hydraulic control system. This code triggers when the Engine Control Module (ECM) detects abnormally low voltage in the electrical circuit controlling the PC-EPC (Pressure Compensator - Electronic Pressure Control) solenoid valve on the main hydraulic pump.

This fault directly affects the machine's ability to regulate hydraulic pump output based on load demand. The PC-EPC valve modulates pump displacement by controlling pilot pressure, making it essential for fuel efficiency and responsive hydraulic performance. When this circuit fails, the ZX690LCH-5A may experience reduced productivity and potential engine protection mode activation.

Common Symptoms

• Hydraulic system warning light illuminated on the instrument cluster with reduced hydraulic power
• Loss of fine control during boom, arm, or bucket operations with jerky or sluggish movements
• Engine derate mode activation where maximum RPM is limited to protect components
• Abnormal hydraulic pump noise or whining due to improper pressure compensation
• Increased fuel consumption as the pump cannot properly match hydraulic demand to load

Potential Causes

The most frequent causes for Code 14105-2 on used ZX690LCH-5A excavators include:

• Damaged wiring harness between the ECM and PC-EPC solenoid, particularly at harness routing points near the main pump where vibration causes wire chafing
• Corroded or loose connectors at the solenoid valve or ECM due to exposure to hydraulic fluid leaks or moisture infiltration
• Failed PC-EPC solenoid coil with internal short circuit or broken windings (common after 8,000+ operating hours)
• ECM internal driver circuit failure affecting the solenoid power supply output
• Ground circuit issues where corroded frame ground points create high resistance paths

How to Troubleshoot and Fix Code 14105-2

Step 1: Visual Inspection and Connector Check Locate the PC-EPC solenoid valve on the main hydraulic pump assembly. Disconnect the electrical connector and inspect for corrosion, bent pins, or hydraulic fluid contamination. Check the wiring harness for visible damage, particularly where it passes near rotating components or sharp edges common on used machines.

Step 2: Electrical Testing with Multimeter Using a digital multimeter, measure the solenoid coil resistance. Typical specifications are 3-7 ohms (consult your service manual for exact values). Next, check for voltage supply at the connector with the ignition on—you should see approximately 12V. Test the ground circuit for continuity to the frame; resistance should be less than 1 ohm.

Step 3: Advanced Diagnostics Connect Hitachi Dr.EX diagnostic software to read live data from the ECM. Monitor the PC-EPC command signal versus actual current draw. If commanded current exceeds actual by significant margins, suspect wiring issues. For used excavators, perform a wiggle test on harnesses while monitoring voltage to detect intermittent opens caused by fractured wires inside insulation.

Step 4: Component Replacement and Verification If testing confirms solenoid failure, replace the PC-EPC valve assembly using genuine Hitachi parts. After replacement, clear codes and perform a hydraulic system calibration using diagnostic software to ensure proper pump control response.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Hitachi service manual for your specific serial number and consider professional diagnostics for complex electrical issues.