What is Hitachi ZX210H-5G-HCMC Fault Code 20105-2?

Fault Code 20105-2 indicates a malfunction in the Engine Control Module (ECM) communication circuit, specifically related to CAN bus data transmission errors between the engine controller and the machine's main monitoring system. This code is triggered when the ECM detects irregular or interrupted communication signals on the Controller Area Network (CAN) high or low signal lines.

For the Hitachi ZX210H-5G-HCMC excavator, this fault directly impacts the machine's ability to coordinate engine performance with hydraulic demands. The CAN bus system serves as the central nervous system, allowing the engine ECM, pump controller, and display monitor to share critical operating data. When communication breaks down, the excavator cannot optimize fuel delivery, hydraulic flow, or emissions controls, potentially causing reduced performance and triggering derate modes that limit machine productivity.

Common Symptoms

• Warning lamp illumination on the instrument cluster, often accompanied by a wrench or engine diagnostic icon
• Intermittent loss of engine RPM display or erratic gauge readings on the monitor panel
• Reduced engine power or activation of derate mode, limiting maximum engine speed to 1,500-1,800 RPM
• Hydraulic system sluggishness due to improper communication between engine load demand and pump output
• Inability to access diagnostic information through the standard machine monitor display

Potential Causes

The most common technical causes for Code 20105-2 on used Hitachi excavators include:

• Corroded or damaged CAN bus connectors at the ECM harness junction, particularly the 38-pin main connector which is exposed to vibration
• Harness wire chafing along the right-hand frame rail where the engine harness runs near hydraulic lines—a known wear point on ZX210 models with 4,000+ operating hours
• Failed termination resistors (120-ohm) at either end of the CAN network, causing signal reflection and data corruption
• ECM internal circuit failure due to moisture intrusion through compromised seals on the controller housing
• Voltage supply issues from corroded ground points G203 or G401 located on the engine block mounting bracket

How to Troubleshoot and Fix Code 20105-2

Step 1: Visual Harness Inspection Begin by examining the engine wiring harness from the ECM to the main chassis connector (C201). On used excavators, focus on areas where the harness contacts the frame or hydraulic components. Look for abraded insulation, bent pins, or green corrosion inside connector bodies. Pay special attention to the harness routing near the fuel cooler—this is a common rub point.

Step 2: CAN Bus Electrical Testing Using a digital multimeter, measure resistance between CAN-H and CAN-L terminals at the ECM connector with the key off and harness disconnected. You should read approximately 60 ohms (two 120-ohm termination resistors in parallel). A reading of 120 ohms indicates one missing terminator; open circuit (OL) means broken wiring or both terminators failed.

Step 3: Signal Voltage Verification With the ignition on and Hitachi Dr. EX diagnostic software connected, monitor live CAN bus voltage. CAN-H should read 2.5-3.5V and CAN-L should read 1.5-2.5V during idle communication. Voltage outside this range or erratic fluctuations confirm circuit problems. Check battery voltage at ECM pin B+ (should be 24-28V) and verify clean grounds at G203 and G401.

Step 4: Component Replacement Priority For used machines, replace corroded connectors first before condemning the ECM. Clean all ground connection points with a wire brush and apply dielectric grease. If harness damage is found, repair using CAN-certified twisted-pair wire (not standard automotive wire). Replace termination resistors if testing shows incorrect values. ECM replacement should be the last resort after confirming all wiring and grounds are intact.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Hitachi service manual for your specific serial number range and consider professional diagnostic assistance for complex electrical issues. Improper repairs may cause additional system damage.