Komatsu PC750SE-7 Fault Code E98A: Complete Diagnostic Guide

What is Komatsu PC750SE-7 Fault Code E98A?

Fault Code E98A indicates a malfunction in the engine control system's communication circuit, specifically related to CAN (Controller Area Network) communication errors between the engine ECM (Engine Control Module) and other critical control modules.

This code typically signals that the ECM is unable to properly communicate with peripheral controllers such as the hydraulic control unit, monitor panel, or transmission controller. For the PC750SE-7's Komatsu SAA6D140E-5 engine, this communication breakdown is critical because the integrated control system relies on constant data exchange to optimize fuel injection timing, hydraulic response, and emission controls. When communication fails, the machine may enter a protective derate mode to prevent potential damage.

Common Symptoms

When Code E98A is active on your PC750SE-7, operators typically experience:

• Warning lights illuminated on the monitor panel, often accompanied by error messages indicating communication failure
• Reduced engine power or sudden derate, limiting machine performance to 50-70% of normal output
• Erratic hydraulic response or delayed boom/bucket movements due to interrupted control signals
• Intermittent gauge failures where monitor displays show incorrect readings or go blank
• Engine may start normally but exhibit performance issues under load or after warm-up

Potential Causes

The most common technical causes for E98A on used PC750SE-7 excavators include:

• CAN bus wiring harness damage – particularly at flex points near the engine mount or along the boom base where vibration causes wire chafing
• Corroded or loose connector pins at the ECM harness connection (C101 connector) or monitor panel connections
• Failed termination resistors in the CAN network (120-ohm resistors at network endpoints)
• ECM internal failure or corrupted software, more common in machines with 8,000+ operating hours
• Voltage irregularities from failing alternator or weak batteries causing communication dropouts
• Water intrusion into harness connectors, especially on machines operated in wet conditions

How to Troubleshoot and Fix Code E98A

Step 1: Visual Inspection Begin by inspecting all wiring harnesses between the ECM (located behind the operator cab) and the monitor panel. Look specifically for abraded insulation, pinched wires at mounting brackets, or green corrosion on connector pins. On used excavators, check harness routing near hydraulic lines where heat damage commonly occurs.

Step 2: Connector and Resistance Testing Disconnect the main ECM connector (C101) and inspect for bent pins or moisture. Using a digital multimeter, measure resistance between CAN-High and CAN-Low terminals (typically pins 23 and 24) – you should read approximately 60 ohms with the key off, indicating proper termination resistors. Readings above 100 ohms or open circuit suggest termination failure.

Step 3: Voltage and Communication Verification With the key on (engine off), measure voltage at the ECM power supply pins – should read 24V DC (±2V). Use Komatsu KOMTRAX diagnostic software or a compatible J1939 scan tool to monitor live CAN bus traffic. If no communication is detected, systematically disconnect peripheral modules to isolate the faulty component causing the bus short.

Step 4: Component Replacement If diagnostics point to a specific failed module, replace the harness section or control module as needed. For used machines, always apply dielectric grease to all reconnected pins to prevent future corrosion.

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