What is Komatsu PC450-7 Fault Code E98A?

Fault Code E98A on the Komatsu PC450-7 indicates a communication error between the Engine Control Module (ECM) and the Hydraulic Control Module (HCM), specifically related to CAN bus system failure or interruption. This diagnostic trouble code (DTC) is triggered when the Controller Area Network (CAN) experiences signal loss, degraded data transmission, or complete communication breakdown between these critical control systems.

The CAN bus serves as the digital nervous system for the PC450-7, allowing real-time data exchange between the engine management system and hydraulic controls. When this communication pathway fails, the excavator cannot properly coordinate engine power output with hydraulic demands, severely compromising both performance and safety. For this 45-ton class machine, maintaining proper ECM-HCM communication is essential for optimal fuel efficiency, hydraulic response, and preventing catastrophic system conflicts.

Common Symptoms

• Warning lamp illuminated on the monitor panel with "E98A" displayed on the multifunction screen
• Engine derate mode activated, limiting maximum RPM to approximately 1,200-1,500 to protect systems
• Erratic hydraulic response including delayed boom/arm movements or inconsistent swing speed
• Intermittent power loss during combined operations (simultaneous travel and lifting)
• Multiple secondary codes may appear alongside E98A, particularly those related to hydraulic solenoids or engine sensors

Potential Causes

The most common technical failures triggering E98A on used PC450-7 excavators include:

• CAN bus wiring harness damage at known rub points near the engine mounting area and along the right-side chassis rail where vibration causes insulation wear
• Corroded or loose connector terminals at the ECM (located behind the operator cab) or HCM (mounted near the hydraulic pump)
• Failed termination resistor within the CAN network (120-ohm resistors at network endpoints)
• ECM or HCM internal failure, particularly in machines exceeding 8,000 operating hours
• Voltage irregularities from failing alternator or battery connections affecting module power supply
• Aftermarket modifications or improperly installed monitoring systems interfering with CAN bus integrity

How to Troubleshoot and Fix Code E98A

Step 1: Visual Harness Inspection Begin with a thorough physical examination of the CAN bus wiring harness running between the ECM and HCM. Focus on the section passing along the engine block's right side where heat and vibration create wear points. Check for abraded insulation, pinched wires, or oil contamination on connectors. On used excavators, this harness routing area frequently shows degradation after 5,000+ hours.

Step 2: Connector and Resistance Testing Disconnect the main CAN connectors at both the ECM and HCM. Inspect terminals for corrosion (common in machines operating in wet conditions) and verify pin tension. Using a digital multimeter, measure resistance between CAN-High and CAN-Low terminals—you should read approximately 60 ohms with both modules connected (two 120-ohm termination resistors in parallel). Readings above 80 ohms or below 50 ohms indicate termination resistor failure or wiring issues.

Step 3: Voltage and Communication Verification With ignition on (engine off), measure voltage at the ECM power supply connector. Verify 24V DC supply voltage is stable (within 23-26V range). Using Komatsu diagnostic software (KOMTRAX Plus or PC-compatible KDW), monitor live CAN bus traffic. The software should display active message packets between modules. No data flow confirms communication failure rather than sensor issues.

Step 4: Module-Specific Testing If wiring and power supply test normal, isolate the fault to a specific module. Swap the ECM or HCM with a known-good unit (if available) or send for professional bench testing. Before replacing expensive modules on used equipment, verify the machine's ground connections—corroded chassis grounds frequently cause intermittent communication codes.

Critical Note for Used Excavators: On PC450-7 models with over 6,000 operating hours, always inspect the main wiring harness support brackets near the fuel tank area, as loose brackets allow excessive harness movement causing internal wire fractures that test normal when stationary but fail under vibration.

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Disclaimer: This guide provides general diagnostic information for Code E98A. Hydraulic and electrical system repairs should be performed by qualified technicians with proper training and access to manufacturer service literature. Improper diagnostics may result in equipment damage or safety hazards.