Komatsu PC800-7 Fault Code E98A: Complete Diagnostic Guide

What is Komatsu PC800-7 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 PC800-7 excavator. This code specifically signals that the CAN bus communication network has detected an interruption or degraded signal quality between these two critical control systems.

The PC800-7 relies on continuous data exchange between the ECM and HCM to optimize engine performance relative to hydraulic demand. When this communication fails, the machine cannot properly coordinate power delivery with hydraulic functions, potentially causing significant operational inefficiencies and 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
• Derated engine power or automatic engine speed limitation to protect systems
• Sluggish or erratic hydraulic response, especially during combined functions (swing + boom operations)
• Intermittent loss of fine control over attachments or travel functions
• Monitor display errors showing incomplete or frozen system information

Potential Causes

The most common technical causes for E98A on used PC800-7 excavators include:

• CAN bus wiring harness damage at known rub points near the engine mounting brackets or along the right-side frame rail
• Corroded or loose connector pins at the ECM (located behind the operator cab) or HCM (mounted near the hydraulic pump)
• Failed termination resistors within the CAN network causing signal reflection
• ECM or HCM internal failure, though less common than wiring issues
• Voltage supply problems to either control module due to aging main harness or ground connections
• Water intrusion into controller housings from damaged seals—common in high-hour used machines

How to Troubleshoot and Fix Code E98A

Step 1: Visual Inspection Begin by thoroughly inspecting the CAN bus harness (typically twisted orange/green wire pair) from the ECM to the HCM. On used excavators, check for harness wear at the engine firewall pass-through and where cables contact the frame. Look for abraded insulation, pinched wires, or previous repair attempts.

Step 2: Connector Examination Disconnect and inspect both the ECM connector (usually a 48-pin connector) and HCM connector. Check for:

• Green corrosion on pins (indicates moisture intrusion)
• Bent or pushed-back pins
• Cracked connector housings

Clean contacts with electrical contact cleaner and apply dielectric grease before reconnection.

Step 3: Electrical Testing Using a digital multimeter, measure CAN-High and CAN-Low voltage at both modules with ignition on, engine off. You should see approximately 2.5V on each line with 0V differential. Check for 120-ohm resistance between CAN-High and CAN-Low with modules disconnected (indicates proper termination).

Step 4: Advanced Diagnostics Connect Komatsu KOMTRAX diagnostic software or compatible scan tool to monitor real-time CAN bus traffic. Look for message dropout patterns that indicate intermittent failures. Check supply voltage to both modules (should be 24V ±2V).

Step 5: Component Replacement If wiring and connections test good, the issue likely resides in a control module. For used machines, consider testing modules in a known-good excavator before purchasing replacements, as ECM and HCM units are expensive components.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific machine serial number and consider professional diagnostic services for complex electrical issues. Improper repairs may cause additional system damage.