What is Komatsu Fault Code E135DW4AKA?

Komatsu fault code E135DW4AKA indicates a communication error or malfunction within the machine's Controller Area Network (CAN) bus system, specifically related to data transmission between the engine ECM (Engine Control Module) and the machine controller or display unit. This code typically appears when there's an interruption, voltage irregularity, or complete failure in the digital communication network that allows different electronic control units to share critical operational data.

The CAN bus system is the backbone of modern Komatsu excavators, enabling real-time communication between the engine, hydraulic systems, transmission, and operator display. When code E135DW4AKA triggers, it means the ECM cannot properly send or receive data packets, which can compromise machine performance monitoring, diagnostic capabilities, and even operational safety features. For used excavators, this code is particularly concerning as it often indicates aging wiring harnesses, corroded connectors, or failing control modules that have degraded over thousands of operating hours.

Common Symptoms

• Warning lights illuminated on the instrument cluster, often accompanied by a master caution or check engine light
• Intermittent or complete loss of display functions, including engine RPM, temperature readings, or hydraulic pressure gauges
• Reduced engine power or derate mode activation as the ECM enters a failsafe condition due to communication loss
• Erratic gauge behavior where readings fluctuate randomly or freeze on the monitor panel
• Inability to access diagnostic information through the standard operator interface or monitor screen

Potential Causes

The most common technical causes for fault code E135DW4AKA in used Komatsu excavators include:

• Damaged or corroded CAN bus wiring harness, particularly at known rub points near the swing bearing, boom base, or engine firewall where movement causes abrasion
• Loose or oxidized connector pins at the ECM, machine controller, or display unit connections—extremely common in machines operating in wet or corrosive environments
• Failed terminating resistors within the CAN network, which are essential for proper signal integrity
• ECM or machine controller internal failure, often due to moisture intrusion, vibration damage, or component aging in high-hour machines
• Voltage supply issues to control modules caused by failing alternators, weak batteries, or corroded ground connections
• Aftermarket modifications or previous repairs that incorrectly spliced into the CAN network

How to Troubleshoot and Fix Code E135DW4AKA

Step 1: Visual Inspection of Harnesses and Connectors Begin by thoroughly inspecting all CAN bus wiring harnesses from the ECM to the machine controller and display unit. On used excavators, pay special attention to harness routing near articulation points, hydraulic lines, and the swing bearing where friction and vibration cause insulation wear. Check all connector bodies for corrosion, bent pins, or moisture intrusion. Clean connectors with electrical contact cleaner and apply dielectric grease.

Step 2: Voltage and Continuity Testing Using a digital multimeter, verify that the ECM and machine controller are receiving proper supply voltage (typically 24V for Komatsu equipment). Check for voltage drop across ground connections—readings above 0.2V indicate poor grounding. Test CAN-High and CAN-Low wire continuity between control modules; resistance should be approximately 60 ohms with the key off (indicating proper terminating resistor function). Any open circuit or significantly different resistance suggests wiring damage or resistor failure.

Step 3: Advanced Diagnostics with Komatsu Software Connect Komatsu diagnostic software (KOMTRAX or dealer-level tools) to monitor live CAN bus traffic and identify which specific module is failing to communicate. The software can show message transmission rates and error counters. For used machines, check stored fault history—repeated intermittent codes often point to vibration-induced connector issues rather than hard component failures.

Step 4: Component Replacement and Verification If diagnostics isolate a failed ECM or machine controller, verify the part number matches your specific machine serial number before replacement, as Komatsu uses different software versions. After replacing any component or repairing harnesses, clear all fault codes and perform a complete operational test cycle. Monitor for code recurrence over several hours of operation, as intermittent connection problems may not appear immediately.

Critical Note for Used Equipment: Before replacing expensive control modules, invest time in harness inspection and connector refurbishment—over 60% of CAN communication faults in used excavators stem from connection issues rather than failed electronics.

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Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Komatsu service manual for your specific machine model and serial number. If you lack proper diagnostic tools or experience with electronic control systems, seek assistance from a certified Komatsu technician to avoid costly misdiagnosis or safety hazards.