Hitachi ZX850-3 Fault Code 11404-4: Complete Diagnostic Guide

What is Hitachi ZX850-3 Fault Code 11404-4?

Fault Code 11404-4 indicates a malfunction in the Engine Control Module (ECM) communication circuit, specifically related to CAN (Controller Area Network) bus communication errors or data transmission failures between the engine controller and other machine systems.

This code is part of Hitachi's proprietary diagnostic system for the ZX850-3 excavator, which typically features an Isuzu engine with advanced electronic controls. The CAN bus serves as the central nervous system for the machine, allowing the ECM, hydraulic controllers, and display monitors to exchange critical operational data. When this communication breaks down, the excavator cannot properly coordinate engine performance with hydraulic demands, potentially causing unsafe operating conditions or complete machine shutdown.

Common Symptoms

• Warning lights illuminated on the instrument cluster, particularly the engine malfunction lamp or communication error indicator
• Reduced engine power or derate mode activation, limiting machine performance to protect components
• Erratic gauge readings or complete loss of display information on the monitor panel
• Intermittent loss of hydraulic functions or unresponsive controls due to coordination failures
• Engine may enter limp mode or fail to start if communication is completely lost

Potential Causes

The most common technical causes for Code 11404-4 on used ZX850-3 excavators include:

• Corroded or damaged CAN bus connectors, particularly at the ECM harness connection points behind the cab
• Wiring harness chafing at known rub points near the engine mounting brackets or along the boom base
• Failed termination resistors in the CAN network (typically 120-ohm resistors at network endpoints)
• ECM internal failure or corrupted software, more common in high-hour machines
• Voltage supply issues to the communication circuit due to failing relays or poor ground connections
• Water intrusion into connector housings from damaged seals or cab leaks

How to Troubleshoot and Fix Code 11404-4

Step 1: Visual Inspection Begin with a thorough inspection of all wiring harnesses connected to the ECM and communication modules. On used excavators, check specifically for harness wear where cables route near moving components or sharp edges. Inspect all connector pins for corrosion, bent terminals, or moisture intrusion.

Step 2: Electrical Testing Using a digital multimeter, verify CAN-High and CAN-Low voltage levels at the ECM connector (typically 2.5V at rest, with differential signals during operation). Check for proper termination resistance (should read approximately 60 ohms between CAN-H and CAN-L with network powered down). Verify battery voltage supply to the ECM (should be 24V ±2V).

Step 3: Diagnostic Software Analysis Connect Hitachi Dr.EX diagnostic software or compatible scan tool to read real-time communication data. Monitor for intermittent dropouts or specific module failures. Clear codes and perform a CAN bus integrity test if available in the software.

Step 4: Component Replacement If testing reveals specific failures, replace damaged harness sections, clean and seal connectors with dielectric grease, or replace faulty termination resistors. For used machines, consider replacing the entire ECM harness if multiple wear points exist, as this prevents recurring failures.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Hitachi service manual for your specific machine serial number and consider professional diagnosis for complex electrical issues.