Komatsu PC750LC-7 Fault Code E95A: Complete Diagnostic Guide

What is Komatsu PC750LC-7 Fault Code E95A?

Fault Code E95A indicates a malfunction in the engine control system's communication circuit, specifically related to the CAN (Controller Area Network) bus communication error between the engine controller (ECM) and the machine controller (MCU).

This code triggers when the Engine Control Module (ECM) detects abnormal or interrupted data transmission on the CAN communication line. The PC750LC-7 relies on continuous digital communication between multiple controllers to coordinate engine performance, hydraulic functions, and monitoring systems. When this communication fails, the machine cannot properly regulate critical functions, potentially leading to reduced performance or complete shutdown to prevent damage.

This fault is particularly critical because the CAN bus serves as the nervous system of modern excavators, enabling real-time coordination between engine management, hydraulic controls, and operator interface systems.

Common Symptoms

When Code E95A is active, operators typically experience:

• Warning light illumination on the monitor panel, often accompanied by an audible alarm
• Reduced engine power or automatic derate mode, limiting machine performance to protect components
• Erratic hydraulic response or inconsistent implement movement due to communication delays
• Intermittent gauge readings or complete loss of monitor display functions
• Engine shutdown in severe cases where the ECM cannot verify safe operating parameters

Potential Causes

The most common technical causes for E95A on used PC750LC-7 excavators include:

• Damaged or corroded CAN bus wiring harness, particularly at flex points near the engine mounting or cab pivot areas where vibration causes wire chafing
• Loose or corroded connector pins at the ECM, MCU, or junction box connections—common in machines exposed to moisture or extreme environments
• Failed termination resistors on the CAN network, typically located at network endpoints
• ECM or MCU internal failure, though less common than wiring issues in used equipment
• Voltage supply problems affecting controller power, including weak batteries or failing alternators
• Aftermarket component interference from improperly installed accessories that disrupt CAN communication

How to Troubleshoot and Fix Code E95A

Step 1: Visual Inspection Begin with a thorough physical examination of all wiring harnesses between the ECM (located near the engine) and MCU (typically in the cab area). Look for obvious damage, chafing, pinched wires, or corroded connectors. On used excavators, pay special attention to harness routing through high-vibration areas and where cables pass through bulkheads.

Step 2: Connector and Voltage Testing Disconnect and inspect all CAN bus connectors for corrosion, bent pins, or moisture intrusion. Clean contacts with electrical contact cleaner. Using a digital multimeter, verify supply voltage to both the ECM and MCU (should read approximately 24V on this model). Check for proper ground continuity (less than 1 ohm resistance to chassis ground).

Step 3: CAN Bus Resistance Check With the ignition off and controllers disconnected, measure resistance across the CAN-High and CAN-Low terminals. You should read approximately 60 ohms, indicating proper termination resistors. A reading of 120 ohms suggests one terminator has failed; infinite resistance indicates an open circuit in the network.

Step 4: Advanced Diagnostics Connect Komatsu KOMTRAX or compatible diagnostic software to read detailed fault data and monitor live CAN bus traffic. This can identify whether communication failures are intermittent or constant, and which controller is failing to respond. For used machines, perform a "wiggle test" by gently moving harnesses while monitoring communication to locate intermittent connection failures.

Step 5: Component Replacement If wiring and connections test properly, suspect controller failure. However, on used excavators, harness replacement resolves E95A in approximately 70% of cases. Always replace damaged sections with OEM-spec shielded twisted-pair cable and ensure proper routing away from high-current wires and hydraulic lines.

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Disclaimer: This guide provides general diagnostic information for Code E95A. Always consult the official Komatsu service manual for your specific machine serial number, and consider engaging a certified Komatsu technician for complex electrical diagnostics. Improper troubleshooting can cause additional damage to electronic control systems.