What is Hitachi ZX870-5A Fault Code 14106-2?

Fault Code 14106-2 on the Hitachi ZX870-5A excavator indicates a malfunction in the Engine Speed Sensor Circuit, specifically a signal voltage abnormality or intermittent connection issue. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an irregular voltage pattern from the engine speed sensor (also known as the crankshaft position sensor), which monitors crankshaft rotation speed and position.

This code is critical for the ZX870-5A's performance because the engine speed sensor provides essential data for proper fuel injection timing, engine load calculations, and overall power management. When this sensor circuit fails or provides erratic signals, the ECM cannot accurately control combustion events, potentially leading to reduced power output, rough idling, or complete engine shutdown to prevent damage.

Common Symptoms

When fault code 14106-2 is active on your Hitachi ZX870-5A, operators typically experience:

• Engine warning light illuminated on the instrument cluster with possible engine derate mode activation
• Difficulty starting the engine, with extended cranking times or intermittent no-start conditions
• Rough idling or irregular engine RPM fluctuations, particularly noticeable at low idle speeds
• Loss of power during operation, especially under heavy loads or during hydraulic-intensive tasks
• Sudden engine stalling without warning, particularly on used machines with aged electrical components

Potential Causes

The most common technical reasons for code 14106-2 appearing on used ZX870-5A excavators include:

• Damaged or corroded sensor connector at the engine speed sensor mounting location (common failure point due to heat and vibration exposure)
• Worn or broken wiring harness between the sensor and ECM, especially at known rub points near the engine block or frame rails
• Failed engine speed sensor due to internal component degradation or heat-related failure
• ECM internal fault or corrupted calibration files (less common but possible in high-hour machines)
• Poor ground connections at the sensor mounting point or ECM ground straps showing corrosion
• Contaminated sensor tip with metal shavings or debris affecting magnetic field detection

How to Troubleshoot and Fix Code 14106-2

Step 1: Visual Inspection Begin by locating the engine speed sensor on the flywheel housing. Inspect the sensor connector for corrosion, bent pins, or moisture intrusion. On used excavators, check the wiring harness routing for signs of rubbing against engine components, heat damage from exhaust manifolds, or rodent damage—common issues in machines with 5,000+ operating hours.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals (typically 190-250 ohms for Hitachi sensors, but verify with service manual specifications). Check for continuity in the wiring harness from sensor to ECM connector. Inspect voltage supply at the sensor connector with ignition on (should read approximately 5V or 12V depending on sensor type).

Step 3: Signal Testing and Component Replacement Connect Hitachi diagnostic software (Dr.EX or compatible diagnostic tool) to monitor real-time sensor signal during cranking. An erratic or missing signal confirms sensor failure. Clean the sensor mounting area and check the air gap between sensor tip and flywheel teeth (typically 0.5-1.5mm). Replace the sensor if readings are out of specification, ensuring proper torque during installation.

Step 4: Harness and Ground Verification For persistent codes on used machines, trace the entire sensor harness for hidden damage. Clean and tighten all ground connections at the engine block and ECM mounting points. Apply dielectric grease to connectors to prevent future corrosion.

Disclaimer: This guide provides general troubleshooting information for the Hitachi ZX870-5A. Always consult the manufacturer's service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs may cause additional damage or safety hazards.