What is Hitachi ZX890H-5A Fault Code 14105-2?

Fault Code 14105-2 indicates a hydraulic pump solenoid valve circuit malfunction, specifically detecting an abnormal voltage or current signal in the proportional pressure control solenoid for the main hydraulic pump. This code is triggered when the machine's Electronic Control Module (ECM) detects either an open circuit, short circuit, or improper resistance values in the pump control solenoid wiring harness.

This fault is critical for the ZX890H-5A's performance because the proportional solenoid directly regulates hydraulic pump displacement and system pressure. When this circuit malfunctions, the excavator cannot properly modulate hydraulic flow to match operational demands, resulting in compromised digging force, reduced fuel efficiency, and potential damage to hydraulic components due to unregulated pressure spikes.

Common Symptoms

When fault code 14105-2 is active, operators typically experience:

• Reduced hydraulic power across all functions, with noticeably slower boom, arm, and bucket movements
• Erratic hydraulic response where attachments move inconsistently or surge unexpectedly during operation
• Warning light activation on the instrument cluster, often accompanied by a diagnostic trouble code display
• Engine derating or automatic RPM reduction as the ECM enters protective mode
• Intermittent functionality where hydraulic power fluctuates between normal and severely limited, especially during temperature changes

Potential Causes

The most common technical reasons for this fault code in used ZX890H-5A excavators include:

• Damaged solenoid connector pins or corroded terminals due to moisture intrusion in the engine compartment
• Wiring harness chafing at known rub points near the hydraulic pump mounting bracket and along the main boom pivot
• Failed proportional solenoid valve caused by internal coil degradation or contaminated hydraulic fluid creating stuck spool valves
• ECM voltage supply issues stemming from aging main power harnesses or poor ground connections at the frame mounting points
• Hydraulic fluid contamination causing the solenoid valve to stick, increasing electrical current draw beyond acceptable parameters

How to Troubleshoot and Fix Code 14105-2

Step 1: Visual Inspection and Connector Check Begin by locating the main hydraulic pump solenoid valve on the pump housing. Disconnect the electrical connector and inspect for corrosion, bent pins, or moisture contamination. On used excavators, this connector frequently shows green corrosion due to seal degradation. Clean contacts with electrical contact cleaner and apply dielectric grease.

Step 2: Electrical Circuit Testing Using a digital multimeter, measure resistance across the solenoid terminals with the connector disconnected. Typical resistance should read between 8-15 ohms (consult your service manual for exact specifications). Next, check for continuity to ground on each wire—any reading below infinite resistance indicates a short circuit requiring harness replacement.

Step 3: Voltage Supply Verification Reconnect the solenoid connector and back-probe the harness connector at the ECM side. With ignition on and engine off, verify battery voltage (12-14V) is present on the power supply wire. Use Hitachi Dr.EX diagnostic software to command the solenoid valve while monitoring actual voltage output versus commanded output.

Step 4: Harness and Routing Inspection Trace the entire wiring harness from the pump to the ECM, paying special attention to areas where the harness passes near sharp edges, rotating components, or heat sources. In used ZX890H-5A machines, common wear points include the harness routing near the swing bearing and where cables enter the main control valve block. Replace any sections showing insulation damage.

Step 5: Component Replacement If electrical tests confirm proper voltage and resistance but the code persists, replace the proportional solenoid valve assembly. Before installation, flush the hydraulic system and replace filters to prevent contamination-related repeat failures.

---

Disclaimer: This guide provides general troubleshooting information. Always consult the official Hitachi service manual for your specific machine serial number and software version. Complex hydraulic and electrical diagnostics should be performed by certified technicians with proper training and equipment.