What is Hitachi ZX870LC-5A Fault Code 14105-2?

Fault Code 14105-2 on the Hitachi ZX870LC-5A excavator indicates a communication error or abnormal signal from the Engine Control Module (ECM) to the Machine Control Module (MCM), specifically related to engine speed sensor data transmission. This diagnostic trouble code (DTC) is triggered when the machine's MCM fails to receive proper engine RPM information from the ECM within the expected parameters, or when signal quality degrades below acceptable thresholds.

This code is critical for the ZX870LC-5A because the MCM relies on accurate engine speed data to coordinate hydraulic pump output, control engine load management, and execute automatic idle functions. Without reliable communication between these two primary control units, the excavator cannot optimize fuel efficiency or protect the engine from overload conditions during heavy digging operations.

Common Symptoms

• Engine derate mode activating, limiting maximum RPM to approximately 1,500-1,800 RPM regardless of throttle input
• Intermittent or constant warning light on the instrument cluster, often accompanied by an audible alarm
• Erratic tachometer readings or complete tachometer failure on the operator display
• Hydraulic system performance reduction, particularly noticeable during combined functions like boom lift with swing
• Automatic engine shutdown in severe cases, especially during cold starts or after extended idle periods

Potential Causes

The most common technical causes for Code 14105-2 on used ZX870LC-5A excavators include:

• Corroded or loose connector pins at the ECM or MCM harness connections, particularly the 38-pin main engine harness connector
• Wiring harness damage near the engine firewall where harnesses pass through grommets—a known rub point on high-hour machines
• Failed engine speed sensor (magnetic pickup type) due to internal coil deterioration or contamination buildup
• ECM internal fault affecting the CAN bus communication circuit, more common in machines exceeding 8,000 operating hours
• Voltage supply issues from the main power distribution module, including poor ground connections at the battery tray mounting points

How to Troubleshoot and Fix Code 14105-2

Step 1: Visual Inspection and Connector Service Begin by inspecting the ECM and MCM wiring harnesses for obvious damage, particularly at known friction points near the engine mount brackets. Disconnect the main 38-pin ECM connector and inspect for green corrosion, bent pins, or moisture intrusion. Clean contacts with electrical contact cleaner and apply dielectric grease before reconnection.

Step 2: Verify Communication Signals Using Hitachi Dr.EX diagnostic software or a compatible CAN bus scanner, monitor real-time communication between the ECM and MCM. Check for consistent engine speed signal transmission while cranking the engine. If no signal appears, use a digital multimeter to test the engine speed sensor output—expect approximately 0.5-2.0 VAC while cranking.

Step 3: Test Sensor and Harness Continuity Measure resistance across the engine speed sensor terminals (typically 200-400 ohms for this model). Inspect the sensor air gap at the flywheel ring gear; proper clearance should be 0.5-1.5mm. For used excavators, check harness continuity from sensor to ECM, paying special attention to wire insulation condition where harnesses route along the engine block.

Step 4: Address Root Cause Replace faulty components as identified. For used machines with over 6,000 hours, consider replacing the entire engine-to-chassis harness section if multiple abrasion points exist, preventing future intermittent faults.

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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 diagnostic assistance for complex electrical issues.