Komatsu Fault Code E457: Complete Technical Guide

What is Komatsu Fault Code E457?

Fault Code E457 indicates a malfunction in the Engine Controller (ECM) communication circuit, specifically a CAN Bus communication error between the engine control module and other machine systems. This code appears when the Controller Area Network (CAN) experiences data transmission failures, preventing critical components from exchanging operational information.

In Komatsu excavators, the CAN Bus system serves as the central nervous system, linking the engine ECM, hydraulic controller, monitor panel, and various sensors. When E457 triggers, the machine's integrated systems cannot properly coordinate, potentially affecting engine performance, hydraulic responsiveness, and operator interface functions. This fault is particularly critical because modern Komatsu equipment relies heavily on electronic communication for optimal performance and safety monitoring.

Common Symptoms

When E457 is active, operators typically experience:

• Warning light illumination on the instrument cluster, often accompanied by a check engine light or master caution indicator
• Intermittent or complete loss of monitor display functions, including gauge readings and operational data
• Reduced engine power or activation of derate mode as a protective measure
• Erratic hydraulic behavior, such as inconsistent boom or bucket response due to communication delays
• Multiple fault codes appearing simultaneously as various controllers lose communication

Potential Causes

The most common technical reasons for E457 in used Komatsu excavators include:

• Damaged CAN Bus wiring harness, particularly at known rub points near the engine bay, turret rotation area, or along the boom where cables flex repeatedly
• Corroded or loose connector pins at the ECM, junction boxes, or controller connections—extremely common in machines operating in wet or coastal environments
• Failed termination resistor in the CAN network (typically 120-ohm resistors at network endpoints)
• ECM internal failure or corrupted software, though less common than wiring issues
• Voltage supply problems to the CAN Bus system, often caused by deteriorated ground connections or failing batteries in older machines
• Water intrusion into sealed connectors, creating intermittent shorts or high resistance

How to Troubleshoot and Fix Code E457

Step 1: Visual Inspection Begin with a thorough examination of all wiring harnesses associated with the CAN network. Focus on areas where cables route through tight spaces or experience movement. Look for abraded insulation, pinched wires, or connector corrosion. On used excavators, check the main engine harness where it passes through the firewall and the turret harness at rotation points.

Step 2: Connector and Ground Testing Disconnect and inspect all CAN Bus connectors, cleaning terminals with electrical contact cleaner. Using a digital multimeter, verify proper ground continuity (should read less than 0.5 ohms to chassis ground). Check battery voltage at the ECM—should read 12-14V with engine off, 13.5-14.5V running.

Step 3: CAN Bus Circuit Verification With Komatsu diagnostic software (KOMTRAX Plus or compatible scan tool), monitor CAN Bus activity. Measure resistance between CAN-High and CAN-Low terminals with all controllers disconnected—should read approximately 60 ohms (two 120-ohm termination resistors in parallel). If open circuit or incorrect readings appear, locate and replace faulty termination resistors.

Step 4: Signal Testing With ignition on, engine off, measure voltage on CAN-High (typically 2.5-3.5V) and CAN-Low (typically 1.5-2.5V) relative to ground. Significant deviation indicates wiring shorts or controller failures. For used equipment, pay special attention to harness repair sections from previous work, as improper repairs frequently cause intermittent communication faults.

Step 5: Component Replacement If wiring and connections test satisfactory, suspect ECM failure. Before replacement, update ECM software using manufacturer diagnostics, as software corruption occasionally causes communication errors. Replace the ECM only after confirming all external circuits are intact.

---

Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult official Komatsu service manuals for model-specific procedures, torque specifications, and safety protocols. Complex electrical diagnostics may require factory-trained technicians with specialized equipment. Improper repairs can cause additional damage or safety hazards.