Komatsu PC750SE-7 Fault Code E95A: Complete Diagnostic Guide

What is Komatsu PC750SE-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 ECM (Engine Control Module) and other critical control modules.

This code triggers when the engine ECM detects abnormal or interrupted data transmission across the CAN bus network, which is the digital communication backbone connecting the engine controller, hydraulic controller, and monitor panel. For the PC750SE-7, this communication failure is critical because it prevents proper coordination between engine performance, hydraulic functions, and operator interface systems, potentially causing the machine to enter a protective derate mode or experience erratic behavior.

Common Symptoms

When Code E95A is active, operators typically experience:

• Warning light illumination on the monitor panel with reduced engine power output
• Intermittent or complete loss of monitor display functions (gauges reading incorrectly or going blank)
• Engine derate mode activation, limiting RPM to protect the machine
• Erratic hydraulic response or inconsistent implement control due to communication loss
• Multiple fault codes appearing simultaneously as various controllers lose synchronization

Potential Causes

The most common technical causes for E95A on used PC750SE-7 excavators include:

• CAN bus wiring harness damage from rubbing against frame components, particularly near the engine firewall and along the right-hand chassis rail (known wear point on this model)
• Corroded or loose connector pins at the ECM harness connector (C101) or hydraulic controller connector
• Failed termination resistors within the CAN network causing signal reflection and data corruption
• ECM internal failure or corrupted software requiring reprogramming
• Water intrusion into harness connectors from damaged grommets or failed seals in the engine compartment
• Aftermarket component interference from improperly installed accessories disrupting CAN signals

How to Troubleshoot and Fix Code E95A

Step 1: Visual Inspection Begin by thoroughly inspecting all CAN bus harness routing from the ECM to the hydraulic controller and monitor. Look specifically for harness chafing against the engine mount brackets and frame rails. Check all connector boots for cracks and examine pins for corrosion or bent contacts—common in used machines with 5,000+ hours.

Step 2: Electrical Testing Using a digital multimeter, measure CAN-High and CAN-Low resistance between the ECM connector terminals (typically pins 23 and 24). You should read approximately 60 ohms with the key off, indicating proper termination. Check for voltage presence (2.5V nominal on each line with key on). Use Komatsu KOMTRAX diagnostic software or compatible scan tool to monitor live CAN bus traffic and identify which module is dropping communication.

Step 3: Component-Level Diagnosis If wiring tests pass, inspect the 120-ohm termination resistors at network endpoints—these frequently fail in high-vibration environments. Test ECM ground circuits for resistance below 1 ohm. For used excavators, remove and clean all CAN network connectors with electrical contact cleaner, as oxidation builds up over time. If the fault persists after harness repair, ECM replacement or reprogramming may be necessary.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific serial number and consider professional diagnosis for complex electrical issues, especially before replacing expensive components like the ECM.