What is Hitachi Excavator Fault Code 11957-4?

Fault Code 11957-4 on Hitachi excavators indicates a communication error or signal malfunction in the machine's Controller Area Network (CAN) bus system, specifically related to data transmission irregularities between the Engine Control Module (ECM) and other critical electronic control units. This code typically points to either a complete loss of communication or intermittent signal disruptions on the CAN network.

This fault is critical because the CAN bus serves as the central nervous system for modern Hitachi excavators, enabling real-time data exchange between the engine controller, hydraulic system controllers, and instrument cluster. When Code 11957-4 appears, the machine's integrated systems cannot properly coordinate, potentially leading to reduced performance, safety system failures, or complete operational shutdown. For used excavators, this code often reveals age-related wiring deterioration or connector corrosion that compromises signal integrity.

Common Symptoms

• Warning lights illuminate on the instrument panel, including check engine light and communication error indicators
• Reduced engine power or derate mode activation, limiting machine performance to protect systems
• Erratic gauge behavior with speedometer, fuel level, or temperature readings fluctuating or becoming unresponsive
• Hydraulic function irregularities including inconsistent response times or unexpected activation of attachment controls
• Intermittent shutdowns where the machine enters limp mode or refuses to start despite adequate fuel and battery voltage

Potential Causes

The most common technical causes for Code 11957-4 in used Hitachi excavators include:

• CAN bus wiring harness damage from abrasion at known rub points near the engine firewall or along the boom pivot area
• Corroded or loose connector terminals at the ECM, transmission controller, or main harness junction boxes
• Failed termination resistors at either end of the CAN network (typically 120-ohm resistors)
• ECM internal circuit failure or software corruption requiring module replacement or reprogramming
• Voltage irregularities in the machine's electrical system causing signal interference on the CAN lines
• Aftermarket component installation with incompatible communication protocols disrupting network traffic

How to Troubleshoot and Fix Code 11957-4

Step 1: Visual Inspection Begin with a thorough examination of all wiring harnesses along the main chassis, paying special attention to areas where cables pass through metal frames or near moving components. Check all connector pins at the ECM and related control modules for corrosion, bent pins, or moisture intrusion—common issues in used machines operating in harsh environments.

Step 2: Electrical Testing Using a digital multimeter, measure CAN bus voltage at the diagnostic connector. You should observe approximately 2.5V on both CAN-High and CAN-Low lines with ignition on, engine off. Check termination resistance by measuring across CAN-High and CAN-Low with all modules disconnected—you should read approximately 60 ohms (two 120-ohm resistors in parallel). Deviations indicate failed resistors or wiring shorts.

Step 3: Advanced Diagnostics Connect Hitachi diagnostic software (Dr.EX or equivalent) to monitor real-time CAN bus traffic and identify which specific module is dropping communication. Inspect the ECM ground connections for high resistance—clean and tighten all ground points. For used excavators, consider replacing the entire main harness connector at the ECM if terminals show any discoloration, as intermittent connections are difficult to isolate.

Step 4: Component Replacement If diagnostics isolate a specific module, replace the faulty control unit with OEM or verified compatible parts. After any repairs, clear codes and perform a complete system operational test under load to verify proper communication restoration.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Hitachi service manual for your specific model and consider engaging a certified heavy equipment technician for complex electrical diagnostics and repairs.