What is Hitachi ZX670LC-5A Fault Code 20142-2?

Fault Code 20142-2 indicates a malfunction in the hydraulic pump flow control system, specifically a voltage abnormality or communication error in the pump regulator solenoid circuit. This code is generated when the Engine Control Module (ECM) detects an out-of-range signal or electrical irregularity from the main pump's proportional pressure control solenoid valve.

On the Hitachi ZX670LC-5A, this large excavator relies on precise electronic control of its twin variable displacement hydraulic pumps to deliver optimal flow and pressure. When Code 20142-2 triggers, the ECM identifies that the feedback voltage from the pump regulator doesn't match commanded values, threatening hydraulic efficiency and potentially causing the machine to enter a protective derate mode. This is critical because improper pump regulation directly impacts boom speed, bucket breakout force, and overall cycle times—essential performance metrics for this 67-ton class excavator.

Common Symptoms

• Sluggish hydraulic response across all functions, particularly noticeable in combined operations like boom raise with bucket curl
• Intermittent loss of hydraulic power or sudden flow reduction during high-demand tasks
• Warning light activation on the monitor panel, often accompanied by alarm code display
• Engine RPM fluctuation as the ECM attempts to compensate for pump control irregularities
• Reduced swing speed and diminished digging force compared to normal operation

Potential Causes

The most common technical reasons for Code 20142-2 on used ZX670LC-5A excavators include:

• Wiring harness damage at known rub points near the main pump mounting area, especially where cables route around the swivel joint
• Corrosion or moisture intrusion in the pump solenoid connector (typically a 4-pin Deutsch-style connector)
• Failed proportional pressure solenoid valve inside the pump regulator assembly due to internal coil resistance drift
• ECM voltage supply issues stemming from corroded main power harness connections or failing alternator output
• Hydraulic contamination causing mechanical binding of the pump regulator spool, preventing proper electrical response

How to Troubleshoot and Fix Code 20142-2

Step 1: Visual Inspection Begin by examining the pump solenoid wiring harness from the ECM to both main pumps. On used excavators, check for cable wear where the harness passes through the upper structure near the hydraulic tank. Inspect all connector pins for corrosion, bent terminals, or oil contamination. Clean connectors with electrical contact cleaner and apply dielectric grease.

Step 2: Electrical Testing Using a digital multimeter, disconnect the pump solenoid connector and measure resistance across the solenoid coil terminals—specification typically ranges 8-12 ohms for this model. Check for proper supply voltage (approximately 12-14V with key on) at the harness connector. Verify ground circuit continuity to chassis.

Step 3: Solenoid Function Test With Hitachi diagnostic software (Dr.EX) connected via the diagnostic port, command the pump solenoid through various duty cycles while monitoring real-time feedback voltage. Compare actual versus commanded values—deviations exceeding 0.5V typically indicate solenoid failure.

Step 4: Component Replacement If testing confirms solenoid failure, replacement requires draining the affected pump circuit and removing the regulator cover. For used machines over 8,000 hours, consider replacing both pump solenoids preventatively, as they experience identical wear patterns. Always use genuine Hitachi parts to maintain valve response specifications.

Disclaimer: This guide provides general troubleshooting information. Hydraulic system diagnostics on large excavators involve high-pressure components and complex electronics. Always consult factory service manuals and consider professional certified technician assistance for proper diagnosis and repair.