What is Hitachi ZX670LC-5A Fault Code 14104-2?

Fault Code 14104-2 indicates an abnormal signal detected in the Engine Oil Pressure Sensor circuit, specifically a voltage reading that is higher than the expected range (high voltage condition). This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) receives a sensor voltage signal that exceeds the manufacturer's predetermined threshold, typically above 4.5-4.8 volts in the sensor circuit.

This fault code directly affects the ZX670LC-5A's Isuzu AH-6WG1X engine monitoring system. The oil pressure sensor is critical for protecting the engine from catastrophic damage due to insufficient lubrication. When this code is active, the ECM cannot accurately monitor actual engine oil pressure, potentially leading to unsafe operating conditions or unnecessary engine derates that impact jobsite productivity.

Common Symptoms

When fault code 14104-2 is active on your ZX670LC-5A, operators typically experience:

• Engine warning light illuminated on the instrument cluster or monitor panel
• Possible engine derate or power reduction mode, limiting machine performance to protect the engine
• Erratic oil pressure gauge readings showing abnormally high or fluctuating values on the display
• Intermittent alarm buzzer activation, particularly during startup or varying engine loads
• Stored fault code in ECM memory even if symptoms are not continuously present

Potential Causes

The most common technical causes for fault code 14104-2 on used ZX670LC-5A excavators include:

• Open circuit in sensor wiring harness caused by wire breakage, corrosion, or connector damage
• Failed engine oil pressure sensor with internal electrical fault causing high resistance or open signal
• Damaged or corroded sensor connector pins – particularly common in machines exposed to harsh environments
• Chafed wiring at known rub points near the engine mount or along the frame rail where harnesses contact metal edges
• Faulty ECM internal circuitry (less common) affecting the 5-volt reference supply to the sensor
• Poor ground connection at the sensor or ECM ground points due to corrosion buildup on used equipment

How to Troubleshoot and Fix Code 14104-2

Step 1: Visual Inspection Begin by locating the engine oil pressure sensor on the Isuzu engine block (typically mounted on the main oil gallery). Thoroughly inspect the sensor connector and wiring harness for obvious damage, corrosion, bent pins, or oil contamination. On used excavators, pay special attention to harness routing near vibration points and areas where wires may have rubbed against sharp edges over thousands of operating hours.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and check the supply voltage at the harness connector with the ignition on. You should read approximately 5 volts on the reference wire. Check for proper ground continuity (less than 1 ohm resistance to chassis ground). If voltage is absent or ground is poor, trace the wiring back toward the ECM checking for breaks or damaged insulation.

Step 3: Sensor Resistance Testing Test the oil pressure sensor resistance with the sensor removed. While specifications vary, most sensors should show changing resistance when mechanical pressure is simulated. A reading of infinite resistance (open circuit) or near-zero resistance (short circuit) indicates sensor failure. Replace with genuine Hitachi/Isuzu parts for reliable operation.

Step 4: Advanced Diagnostics Connect Hitachi Dr.EX diagnostic software or compatible scan tool to read live sensor data. Monitor the sensor voltage output while the engine is running. Normal operation shows voltage varying between 0.5-4.5 volts depending on oil pressure. Constant high voltage (above 4.8V) with the sensor connected confirms sensor or wiring fault.

Step 5: Repair and Verification Replace damaged components (sensor, connectors, or repair harness). Clear the fault code using diagnostic software, run the engine through multiple operating cycles, and verify the code does not return. For used equipment, apply dielectric grease to connectors to prevent future corrosion.

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Disclaimer: This guide provides general troubleshooting information for Hitachi ZX670LC-5A fault code 14104-2. Always consult the official Hitachi service manual for your specific machine serial number and follow proper safety procedures. If you're uncomfortable performing electrical diagnostics, contact a certified Hitachi technician or qualified heavy equipment mechanic for professional assistance.