Hitachi ZX870LCH-3 Fault Code 11404-3: Complete Diagnostic Guide

What is Hitachi ZX870LCH-3 Fault Code 11404-3?

Fault Code 11404-3 indicates a malfunction in the Engine Control Module (ECM) communication circuit, specifically related to a CAN (Controller Area Network) bus communication error or timeout condition. This code triggers when the ECM loses proper data transmission with other critical control modules within the machine's electronic network.

In the ZX870LCH-3, this fault affects the integrated communication between the engine controller, hydraulic control unit, and monitor display system. The CAN bus serves as the central nervous system for this excavator, coordinating real-time data between multiple systems. When communication breaks down, the machine cannot properly regulate engine performance, hydraulic functions, or provide accurate operator feedback, making this a critical diagnostic priority.

Common Symptoms

When Code 11404-3 is active, operators typically experience:

• Warning lights illuminated on the monitor panel, often accompanied by error messages indicating communication failure
• Intermittent or complete loss of gauge readings (fuel level, coolant temperature, hydraulic oil temperature)
• Erratic engine behavior, including unexpected derating or failure to respond to throttle inputs
• Hydraulic system irregularities, such as sluggish response or inability to execute combined functions smoothly
• Machine may enter limp mode or refuse to start entirely, depending on fault severity

Potential Causes

The most common technical causes for this fault code in used ZX870LCH-3 excavators include:

• Corroded or damaged CAN bus connectors at the ECM, particularly the 38-pin main harness connector
• Wiring harness chafing near the engine mounting points or along the right-hand chassis rail (known wear point for this model)
• Failed termination resistors within the CAN network (typically 120-ohm resistors at network endpoints)
• ECM internal failure or corrupted software/firmware
• Water intrusion into junction boxes, especially the main harness junction near the fuel tank
• Voltage irregularities from failing batteries or alternator issues affecting CAN bus power supply (typically 5V reference)

How to Troubleshoot and Fix Code 11404-3

Step 1: Visual Inspection Begin with a thorough physical examination of all wiring harnesses and connectors in the CAN network. Focus on the ECM connector (located behind the operator cab on the right side), checking for corrosion, bent pins, or moisture. Inspect harness routing near the engine mounts and swing bearing area where vibration causes wear on used machines.

Step 2: Electrical Testing Using a digital multimeter, verify CAN-High and CAN-Low voltage at the ECM connector. With ignition on, you should measure approximately 2.5V on both lines at rest. Check termination resistance between CAN-High and CAN-Low pins—you should read approximately 60 ohms (two 120-ohm resistors in parallel). Readings outside 55-65 ohms indicate termination resistor failure.

Step 3: Advanced Diagnostics Connect Hitachi Dr.EX diagnostic software to read real-time CAN bus activity and pinpoint which module is dropping communication. Check battery voltage (should maintain 24V minimum) and inspect ground connections at the ECM mounting bracket. For used excavators, remove and clean all ground terminals with electrical contact cleaner, as corrosion here frequently causes intermittent communication faults.

Step 4: Component Replacement If diagnostics isolate a failed component, replace the wiring harness section, ECM, or affected control module. Always apply dielectric grease to connectors during reassembly to prevent future corrosion.

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Disclaimer: This guide provides general diagnostic information. Complex electrical issues should be evaluated by certified Hitachi technicians with proper diagnostic equipment. Always consult the official service manual for your specific machine serial number before performing repairs.