Hitachi ZX870LCH-3 Fault Code 11920-2: Complete Diagnostic Guide

What is Hitachi ZX870LCH-3 Fault Code 11920-2?

Fault Code 11920-2 indicates a malfunction in the Engine Control Module (ECM) communication circuit, specifically a data link error or CAN bus communication failure between the engine controller and other machine systems. This code is part of Hitachi's proprietary diagnostic system for the ZX870LCH-3 excavator.

This fault affects the Controller Area Network (CAN) communication protocol that allows the ECM, hydraulic controllers, and display monitors to exchange critical operational data. When this communication breaks down, the machine cannot properly coordinate engine performance with hydraulic demands, potentially causing reduced efficiency or complete operational shutdown. For the ZX870LCH-3's sophisticated Isuzu engine management system, reliable CAN bus communication is essential for optimal fuel injection timing, emissions control, and power delivery.

Common Symptoms

• Dashboard warning lights illuminate, including the engine malfunction indicator and communication error symbols
• Intermittent or complete loss of engine parameter displays on the monitor (RPM, coolant temperature, fuel level)
• Reduced engine power or derate mode activation as a protective measure
• Erratic hydraulic response due to improper engine-hydraulic system coordination
• Difficulty starting or unexpected engine shutdown in severe cases

Potential Causes

The most common technical causes for Code 11920-2 on used ZX870LCH-3 excavators include:

• CAN bus wiring harness damage from rubbing against the chassis near the engine bay or along the boom base—a known wear point on this model
• Corroded or loose connector pins at the ECM or junction box connections, especially on machines with high operating hours in wet environments
• Failed termination resistors on the CAN network (typically 120-ohm resistors at network endpoints)
• ECM internal communication module failure due to voltage spikes or age-related component degradation
• Damaged shielded cable allowing electromagnetic interference from starter motors or alternators

How to Troubleshoot and Fix Code 11920-2

Step 1: Visual Inspection Begin with a thorough physical examination of all CAN bus harness routing from the ECM to the main junction box. On used excavators, check specifically where harnesses pass through bulkheads or near moving components. Look for abraded insulation, pinched wires, or evidence of previous repairs.

Step 2: Connector and Resistance Testing Disconnect the ECM connector and inspect for corrosion, bent pins, or moisture intrusion. Using a digital multimeter, measure resistance between CAN-High and CAN-Low terminals—you should read approximately 60 ohms with the system powered off (indicating proper termination resistors). Check continuity along the entire harness length.

Step 3: Voltage and Signal Verification With the ignition on (engine off), measure voltage at the CAN-High line (should read approximately 2.5-3.5V) and CAN-Low line (approximately 1.5-2.5V). Significant deviation indicates a short circuit or open circuit condition.

Step 4: Diagnostic Software Analysis Connect Hitachi Dr.EX diagnostic software or compatible scan tool to read live data and freeze frame information. Monitor CAN bus activity and message error rates to identify which specific controller is failing to communicate.

Step 5: Component Replacement For used machinery, replace suspect harness sections rather than attempting repairs, as aged insulation often fails progressively. If harnesses test good, verify termination resistor integrity before considering ECM replacement.

---

Disclaimer: This guide provides general diagnostic information. Complex electrical issues should be diagnosed by certified Hitachi technicians with proper equipment. Always consult the official service manual and follow safety protocols when working on heavy equipment electrical systems.