Komatsu PC750LC-7 Fault Code E98A: Complete Diagnostic Guide

What is Komatsu PC750LC-7 Fault Code E98A?

Fault Code E98A indicates a communication error between the Engine Control Module (ECM) and the Hydraulic Control Module (HCM) on the Komatsu PC750LC-7 excavator. This code specifically signals that the CAN bus communication network has experienced an interruption or data transmission failure between these two critical control systems.

The PC750LC-7 relies on continuous data exchange between the ECM and HCM to optimize engine performance relative to hydraulic demand. When this communication link fails, the machine cannot properly coordinate power delivery with hydraulic functions, potentially causing significant operational inefficiencies. This is particularly critical in the PC750LC-7, where the CLSS (Closed-Center Load Sensing System) requires real-time coordination between engine output and hydraulic load requirements.

Common Symptoms

When Code E98A is active, operators typically experience:

• Warning light illumination on the monitor panel with reduced machine responsiveness
• Derated engine power or automatic shift to low-power mode as a protective measure
• Sluggish or uncoordinated hydraulic functions, particularly during combined operations (swing + boom movements)
• Intermittent loss of monitor display data showing engine parameters or hydraulic temperatures
• Erratic engine RPM that doesn't respond appropriately to hydraulic load changes

Potential Causes

The most common technical causes for E98A on used PC750LC-7 excavators include:

• CAN bus wiring harness damage at known rub points near the engine mounting brackets or along the right-hand chassis rail
• Corroded or loose connector pins at the ECM (located behind the operator cab) or HCM (mounted near the hydraulic pump)
• Failed termination resistors on the CAN bus network (120-ohm resistors at network endpoints)
• ECM or HCM internal failure, though less common than wiring issues in used machines
• Voltage supply problems to either control module due to aging main harness or poor ground connections
• Water intrusion into connectors from damaged harness boots or failed seals

How to Troubleshoot and Fix Code E98A

Step 1: Visual Inspection Begin with a thorough physical inspection of the CAN bus harness routing between the ECM and HCM. On used excavators, check for harness wear at the engine firewall pass-through and where cables contact the chassis frame. Inspect all connector boots for cracks and examine pins for corrosion or bent contacts.

Step 2: Electrical Testing Using a digital multimeter, verify CAN-High and CAN-Low voltage levels at both the ECM and HCM connectors (engine off, key on). You should measure approximately 2.5V on each line. Check termination resistance by measuring between CAN-High and CAN-Low with modules disconnected—you should read approximately 60 ohms (two 120-ohm resistors in parallel).

Step 3: Diagnostic Software Analysis Connect Komatsu KOMTRAX diagnostic software or compatible scan tool to retrieve detailed communication fault data. Monitor live CAN bus traffic to identify whether communication fails completely or intermittently. Check for additional stored codes that might indicate which module initiated the fault.

Step 4: Connector Service For used machines, thoroughly clean all CAN bus connector pins with electrical contact cleaner and apply dielectric grease before reconnection. Replace any damaged connector seals to prevent future moisture intrusion.

Step 5: Component Replacement If wiring and connections test properly, suspect module failure. The HCM fails more frequently than the ECM in field conditions. Replace suspected modules one at a time and retest.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number and consider professional diagnostic assistance for complex electrical issues.