What is Hitachi ZX350LCK-5G Fault Code 14104-2?

Fault Code 14104-2 indicates a DEF (Diesel Exhaust Fluid) pressure sensor circuit malfunction with an intermittent or erratic signal on the Hitachi ZX350LCK-5G excavator. This code is triggered when the Engine Control Module (ECM) detects abnormal voltage readings or signal interruptions from the DEF pressure sensor, which monitors the pressure within the diesel exhaust fluid injection system.

This fault is critical for the ZX350LCK-5G's Selective Catalytic Reduction (SCR) system performance. The DEF pressure sensor ensures proper urea injection rates to reduce NOx emissions and maintain compliance with Tier 4 Final emission standards. When this sensor malfunctions, the excavator may enter derate mode, significantly reducing engine power and hydraulic performance to protect the aftertreatment system.

Common Symptoms

• Amber or red warning light illuminated on the instrument panel, specifically related to emissions or DEF system
• Engine power derate limiting machine to 50-70% of normal output after a predetermined time period
• Intermittent loss of hydraulic power during operation, especially under heavy loads
• DEF system fault messages displayed on the monitor screen
• Rough engine performance or irregular idle when the sensor signal drops out completely

Potential Causes

The most common technical causes for Code 14104-2 on used ZX350LCK-5G excavators include:

• Corroded or damaged connector pins at the DEF pressure sensor due to exposure to moisture and road salt
• Wiring harness chafing where the sensor cable runs near the DEF tank mounting bracket—a known wear point on this model
• Failed DEF pressure sensor from crystallized urea contamination on the sensor element
• Intermittent ground connection at the sensor harness due to loose mounting bolts or corroded ground straps
• ECM software issues requiring calibration updates (less common but documented on early 5G series machines)
• Frozen or contaminated DEF causing actual pressure fluctuations that appear as sensor faults

How to Troubleshoot and Fix Code 14104-2

Step 1: Visual Inspection Locate the DEF pressure sensor on the DEF supply line near the dosing module. Inspect the wiring harness for visible damage, chafing, or corrosion, paying special attention to where the harness contacts the frame or DEF tank. On used excavators, check for evidence of previous repairs or wire splices that may have degraded.

Step 2: Electrical Testing Disconnect the sensor connector and inspect pins for corrosion or bent terminals. Using a digital multimeter, check for proper supply voltage (typically 5V reference) at the connector with key on, engine off. Measure sensor resistance (typically 200-500 ohms depending on temperature) and compare to factory specifications in the Hitachi service manual.

Step 3: Signal Testing Reconnect the sensor and use Hitachi Dr.EX diagnostic software or compatible scan tool to monitor live data from the DEF pressure sensor. Observe readings during engine operation—the signal should be stable between 0.5-4.5V. Erratic fluctuations or dropouts confirm sensor or wiring failure. Wiggle the harness while monitoring to identify intermittent connections.

Step 4: Component Replacement If electrical tests confirm sensor failure, replace the DEF pressure sensor with a genuine Hitachi part (Part #4679981 or equivalent). Before installation, flush the DEF supply line to remove any crystallized deposits. Apply dielectric grease to connector terminals to prevent future corrosion—critical for used machines operating in harsh environments.

Step 5: System Reset and Verification After repairs, clear fault codes using diagnostic software and perform a DEF system prime cycle. Run the machine through a complete work cycle and monitor for code recurrence. Check that the engine operates at full power without derate.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Hitachi service manual for your specific machine serial number and consider professional diagnosis for complex electrical issues. Improper repairs to emission systems may violate environmental regulations.