Hitachi ZX870H-3 Fault Code 11404-4: Complete Diagnostic Guide

What is Hitachi ZX870H-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 ZX870H-3 excavator, which typically features an Isuzu engine with advanced electronic controls. The CAN bus network serves as the central nervous system for this machine, enabling critical communication between the ECM, hydraulic controllers, and display monitors. When this communication breaks down, the excavator cannot properly coordinate engine performance with hydraulic demands, potentially causing significant operational issues and reduced productivity.

Common Symptoms

• Warning lights illuminated on the instrument cluster, particularly the engine malfunction indicator or communication error lamp
• Intermittent loss of display data on the monitor panel, including engine parameters, fuel consumption, or hydraulic temperatures
• Reduced engine power or unexpected derate mode activation, limiting machine performance to protect systems
• Erratic hydraulic response due to improper coordination between engine output and hydraulic demand
• Difficulty starting or unexpected engine shutdown in severe cases

Potential Causes

The most common technical causes for Code 11404-4 on used ZX870H-3 excavators include:

• Corroded or damaged CAN bus connectors at the ECM, particularly the 38-pin main harness connector prone to moisture intrusion
• Wiring harness damage along known rub points near the engine mounting brackets and along the right-side chassis rail
• Failed termination resistors within the CAN network (typically 120-ohm resistors at network endpoints)
• ECM internal failure or corrupted software, more common in machines with 8,000+ operating hours
• Voltage supply issues from the main power distribution module affecting ECM operation
• Aftermarket component interference from non-OEM monitors or accessories improperly connected to the CAN network

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. On used excavators, focus on areas where harnesses pass through the engine bay bulkhead and near the hydraulic pump mounting area—these are known wear points on the ZX870H-3. Check for abraded insulation, pinched wires, or evidence of rodent damage.

Step 2: Connector and Voltage Testing Disconnect the main ECM connector and inspect for corrosion, bent pins, or moisture. Using a digital multimeter, verify battery voltage (24V nominal) at the power supply pins. Check CAN-High and CAN-Low circuit continuity between the ECM and the display monitor using Hitachi's wiring diagrams (typically pins 22 and 23 on the main connector).

Step 3: CAN Bus Resistance Check With all controllers disconnected, measure resistance across the CAN-High and CAN-Low lines. You should read approximately 60 ohms (two 120-ohm termination resistors in parallel). Readings significantly higher suggest an open circuit or failed terminator; lower readings indicate a short circuit.

Step 4: Diagnostic Software Analysis Connect Hitachi Dr.EX diagnostic software or compatible scan tool to retrieve freeze frame data and monitor live CAN bus traffic. This will identify which specific controller is failing to communicate. For used machines, update ECM firmware if outdated versions are detected.

Step 5: Component Replacement If diagnostics point to ECM failure, ensure replacement units are programmed with the correct machine parameters. For harness issues, repair damaged sections with proper gauge wire and weatherproof connectors rather than replacing entire harnesses when possible—this is more cost-effective for used equipment.

Disclaimer: This guide provides general diagnostic information. Complex electrical issues should be diagnosed by qualified technicians with access to manufacturer-specific tools and documentation. Improper repairs may cause additional damage or safety hazards.