Komatsu PC750-7 Fault Code E98A: Complete Diagnostic Guide

What is Komatsu PC750-7 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 PC750-7 excavator. This code specifically signals that the CAN bus communication link between these two critical control systems has been interrupted or is experiencing data transmission failures.

The PC750-7 relies on continuous communication between the ECM and HCM to coordinate engine power output with hydraulic demand. When this communication fails, the machine cannot properly match engine speed to hydraulic load requirements, resulting in reduced operational efficiency and potential safety concerns. This fault is particularly critical because it affects the integrated control system that distinguishes modern Komatsu excavators from older mechanical models.

Common Symptoms

When Code E98A is active, operators typically experience:

• Warning light illumination on the monitor panel with reduced machine responsiveness
• Engine derating or failure to reach full RPM under load conditions
• Sluggish hydraulic response with delayed boom, arm, or bucket movements
• Intermittent loss of power that may come and go during operation
• Error messages displayed on the multi-function monitor indicating communication faults

Potential Causes

The most common technical causes for E98A on used PC750-7 excavators include:

• Damaged or corroded CAN bus wiring harness between ECM and HCM, particularly at harness routing points near the engine mount or swing bearing where vibration and flexing occur
• Loose or corroded connector pins at either the ECM (located behind the operator cab) or HCM (mounted near the hydraulic pump)
• Failed termination resistor on the CAN bus network causing signal reflection
• Water intrusion into control module connectors from damaged seals or improper maintenance
• ECM or HCM internal failure, though less common than wiring issues in used machines
• Low battery voltage or poor ground connections affecting module power supply

How to Troubleshoot and Fix Code E98A

Step 1: Visual Inspection Begin by inspecting the wiring harness routing between the ECM and HCM. On used excavators, check for harness wear at known rub points near the engine mounting brackets and along the main frame. Look for chafed insulation, pinched wires, or signs of previous repairs. Inspect all connector bodies for corrosion, bent pins, or moisture intrusion.

Step 2: Electrical Testing Using a digital multimeter, verify battery voltage is above 24V (for 24V systems). Check the CAN-High and CAN-Low circuit continuity between ECM and HCM connectors. Measure termination resistance across the CAN bus—it should read approximately 60 ohms with both modules connected. Use Komatsu diagnostic software (KOMTRAX Plus or equivalent) to monitor real-time CAN bus activity and identify which module is failing to communicate.

Step 3: Component Testing and Repair Clean all connector contacts with electrical contact cleaner and apply dielectric grease to prevent future corrosion—critical for used machines operating in harsh environments. If wiring is damaged, repair using proper gauge wire and heat-shrink connections rather than tape. Replace faulty termination resistors if resistance values are incorrect. If all wiring tests pass, the fault likely resides in either the ECM or HCM, requiring module replacement.

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.