What is Hitachi ZX670LC-5A Fault Code 14105-2?

Fault Code 14105-2 indicates a pressure sensor circuit malfunction in the pilot hydraulic system, specifically detecting an abnormal voltage signal from the pilot pressure sensor. This code is triggered when the Engine Control Module (ECM) receives voltage readings outside the predetermined range (typically below 0.5V or above 4.5V) from the pilot pressure sensor circuit.

The pilot hydraulic system on the ZX670LC-5A is critical for precise control of all attachment movements and travel functions. This sensor monitors pilot pressure to ensure smooth, proportional control of hydraulic operations. When this sensor fails or provides erratic signals, the excavator's control responsiveness and operational safety are compromised, potentially leading to unexpected machine behavior or complete loss of hydraulic function.

Common Symptoms

• Control lever sluggishness or complete unresponsiveness to operator inputs, particularly affecting boom, arm, and bucket movements
• Intermittent hydraulic function loss where controls work sporadically or require multiple attempts to engage
• Warning light illumination on the instrument panel with possible audible alarm
• Error message display on the monitor panel specifically referencing pilot pressure or hydraulic system fault
• Reduced machine performance with slower cycle times and diminished breakout force

Potential Causes

The most common technical failures triggering Code 14105-2 on used ZX670LC-5A excavators include:

• Pilot pressure sensor failure due to internal component degradation or contaminated hydraulic oil infiltration
• Wiring harness damage at known rub points near the pilot valve assembly where cables pass through the superstructure swing bearing
• Corroded or loose electrical connectors at the sensor plug, particularly in machines operated in corrosive environments
• ECM internal fault affecting the sensor input circuit processing
• Hydraulic oil contamination causing sensor membrane damage or erratic readings
• Voltage supply issues from the machine's main power distribution affecting sensor excitation voltage

How to Troubleshoot and Fix Code 14105-2

Step 1: Visual Inspection and Connection Verification Begin by locating the pilot pressure sensor mounted on the pilot valve block beneath the operator cab. Disconnect the electrical connector and inspect for corrosion, oil contamination, bent pins, or moisture intrusion. Clean connections with electrical contact cleaner and apply dielectric grease before reconnecting.

Step 2: Sensor Voltage and Resistance Testing Using a digital multimeter (DMM), measure the supply voltage at the sensor connector with the ignition on—it should read approximately 5 volts. Check sensor output voltage while manually applying pressure to the pilot system; voltage should vary smoothly between 0.5V-4.5V. Test sensor resistance (typically 200-400 ohms) and compare against Hitachi specifications.

Step 3: Wiring Harness Continuity Check Trace the sensor harness from the pilot valve to the main wiring loom, checking for damaged insulation, especially where the harness passes through metal brackets or the swing bearing area. Perform continuity tests on all three wires (signal, ground, supply) and verify less than 5 ohms resistance to the ECM.

Step 4: Sensor Replacement and System Verification For used excavators, if sensor readings are erratic or out of specification, replace the pilot pressure sensor with a genuine Hitachi component. After replacement, clear fault codes using Dr.EX diagnostic software or compatible scan tool, and perform operational testing under load.

Critical for Used Equipment: Always inspect hydraulic oil condition and change filters if contamination is suspected, as degraded oil accelerates sensor failure on older machines.

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