What is Hitachi Excavator Fault Code 13944-2?

Fault Code 13944-2 on Hitachi excavators indicates a malfunction in the machine control system communication circuit, specifically relating to a data link error or controller area network (CAN) bus communication failure between the engine control module (ECM) and the main machine controller. This code typically appears when the electronic control units cannot properly exchange operational data, which is essential for coordinated system performance.

This fault is critical because modern Hitachi excavators rely on continuous communication between the ECM, hydraulic controller, and display panel to optimize fuel delivery, hydraulic flow, and operator interface functions. When communication breaks down, the machine may enter a protective derate mode or experience erratic system behavior that compromises productivity and safety on the jobsite.

Common Symptoms

• Warning lights illuminating on the instrument cluster, particularly the check engine light or communication error indicator
• Intermittent or complete loss of monitor display functions, including inability to view operating parameters or system diagnostics
• Reduced engine power or hydraulic response as the system enters limp mode to prevent potential damage
• Erratic gauge readings or flickering display panels indicating unstable data transmission
• Inability to change operating modes (economy, power, etc.) through the cab controls

Potential Causes

The most common technical causes for Code 13944-2 in used Hitachi excavators include:

• Corroded or loose electrical connectors at the ECM, main controller, or junction boxes, particularly prevalent in machines with high operating hours in wet or dusty environments
• Damaged CAN bus wiring harness due to chafing against frame components, especially near articulation points or along the upper structure swing bearing where flexing occurs
• Failed termination resistor in the communication network, which is common in older machines where resistors degrade over time
• ECM or machine controller internal failure, though less common than wiring issues in used equipment
• Low system voltage from a weak battery or failing alternator causing communication dropout during high electrical load conditions
• Aftermarket component interference from improperly installed accessories that disrupt the CAN bus network

How to Troubleshoot and Fix Code 13944-2

Step 1: Visual Harness Inspection Begin by thoroughly inspecting all wiring harnesses between the ECM (typically located near the engine) and the main machine controller (usually in the cab area). Look specifically for damaged insulation, corroded pins in connectors, or evidence of harness rubbing. On used excavators, pay special attention to areas where harnesses pass through bulkheads or near moving components.

Step 2: Connector and Voltage Testing Disconnect and clean all CAN bus connectors using electrical contact cleaner. Inspect for bent pins or moisture intrusion. Using a digital multimeter, verify battery voltage is between 12-14V at the ECM power supply. Check for proper ground continuity (less than 0.5 ohms resistance) at all controller ground points, as corrosion on ground straps is common in aged machines.

Step 3: CAN Bus Communication Testing Using Hitachi diagnostic software (Dr.EX or equivalent) connected through the diagnostic port, monitor real-time CAN bus communication. Check for intermittent dropouts or error frames. Measure resistance between CAN-High and CAN-Low terminals at the ECM connector (should typically read 60 ohms with termination resistors intact). If resistance is incorrect, locate and replace failed termination resistors.

Step 4: Component Isolation If harness and voltage tests pass, systematically disconnect non-essential devices on the CAN network (aftermarket monitors, telematics devices) to identify potential interference sources. For used excavators with multiple previous owners, undocumented modifications often cause communication issues.

Step 5: Controller Replacement Only after confirming wiring integrity should you consider replacing the ECM or machine controller. These components rarely fail without external damage but may require replacement if internal circuitry has failed.

---

Disclaimer: This guide provides general troubleshooting information for Hitachi excavator fault code 13944-2. Always consult the manufacturer's service manual specific to your machine model and serial number. If you lack proper diagnostic tools or experience with heavy equipment electrical systems, consult a certified Hitachi technician to prevent further damage or safety hazards.