What is Hitachi ZX870LC-5A Fault Code 14105-2?

Fault Code 14105-2 indicates a hydraulic pump solenoid valve circuit malfunction in the Hitachi ZX870LC-5A excavator's main hydraulic system. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormal electrical signal or current draw from the hydraulic pump displacement control solenoid valve, which regulates pump output based on operational demands.

This code is critical for the ZX870LC-5A because the pump displacement control system directly affects hydraulic flow efficiency, fuel consumption, and overall machine performance. When this circuit fails, the excavator cannot properly modulate hydraulic pressure, leading to reduced productivity and potential damage to hydraulic components. The Hitachi Common Rail (HCMC) system integration means this fault can also trigger secondary codes affecting engine-hydraulic coordination.

Common Symptoms

• Reduced hydraulic power across all functions, with noticeably sluggish boom, arm, or bucket movements
• Intermittent loss of hydraulic response during heavy digging operations or when multiple functions are activated simultaneously
• Warning lamp illumination on the operator panel, often accompanied by a continuous or intermittent audible alarm
• Erratic engine RPM fluctuations as the ECM attempts to compensate for improper pump load signals
• Increased fuel consumption due to the pump operating at maximum displacement regardless of actual load requirements

Potential Causes

The most common causes for Code 14105-2 on used ZX870LC-5A excavators include:

• Solenoid valve coil failure due to internal short circuits or open windings from thermal stress over time
• Corroded or damaged wiring harness connectors at the pump solenoid, particularly where the harness routes near the hydraulic tank (a known rub point on this model)
• Chafed or pinched wiring along the main chassis harness run between the ECM and hydraulic pump assembly
• ECM internal driver circuit failure affecting the solenoid control output
• Low battery voltage or poor ground connections causing insufficient current delivery to the solenoid valve
• Contaminated hydraulic oil causing mechanical binding of the solenoid spool, increasing electrical resistance

How to Troubleshoot and Fix Code 14105-2

Step 1: Visual Inspection and Connector Check Begin by inspecting the solenoid valve connector on the main hydraulic pump. Disconnect the connector and examine pins for corrosion, bent terminals, or oil contamination (common in used machines). Check the wiring harness routing from the pump to the ECM, particularly where it passes near moving components or sharp edges. Look for abraded insulation or previous repair attempts.

Step 2: Electrical Testing with Diagnostic Tools Using a digital multimeter (DMM), measure the solenoid coil resistance directly at the valve connector (with harness disconnected). Typical specification for this solenoid is 3-8 ohms at room temperature. Next, check for supply voltage at the connector with the ignition on—you should read approximately 12-14 volts. Use Hitachi Dr.EX diagnostic software or compatible scan tool to perform an active solenoid test, monitoring current draw (normal range: 1.5-2.5 amps).

Step 3: Ground Circuit and Harness Continuity Verification Test ground circuit integrity by measuring resistance between the solenoid ground pin and a known good chassis ground (should be less than 0.5 ohms). On used excavators, ground connections often corrode at mounting points. Check for voltage drop during solenoid activation—excessive drop (over 0.5V) indicates poor connections or damaged wiring.

Step 4: Component Replacement and System Verification If electrical tests confirm solenoid failure, replace the pump displacement control solenoid valve assembly. Before installation, clean the mounting surface and apply dielectric grease to connector pins to prevent future corrosion. After replacement, clear fault codes and perform a hydraulic system function test under load. Monitor oil temperature and verify proper pump response across all operational ranges.

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Disclaimer: This guide provides general diagnostic information for Code 14105-2. Hydraulic and electrical systems involve high pressures and voltages. Always consult the official Hitachi service manual for your specific serial number and seek professional assistance from certified Hitachi technicians for complex repairs.