Komatsu PC850-8R Fault Code AB00KE: Complete Diagnostic Guide

What is Komatsu PC850-8R Fault Code AB00KE?

Fault Code AB00KE indicates a communication error or data transmission failure within the Komatsu PC850-8R's CAN (Controller Area Network) bus system, specifically affecting the machine's electronic control modules.

This diagnostic trouble code (DTC) signals that the Engine Control Module (ECM), Hydraulic Control Module, or Monitor Panel is experiencing interrupted or corrupted data exchange. The CAN bus serves as the central nervous system for the PC850-8R, coordinating critical functions between multiple controllers. When communication breaks down, the machine's integrated systems cannot properly synchronize, potentially affecting engine performance, hydraulic response, and operational safety monitoring.

For the PC850-8R—a 187,000-pound ultra-class excavator—reliable CAN communication is essential for coordinating the high-flow hydraulic system with engine load management and preventing component damage during heavy-duty operations.

Common Symptoms

• Warning lights illuminated on the monitor panel, often accompanied by error messages indicating "communication error" or "system malfunction"
• Intermittent loss of gauge readings (fuel level, hydraulic temperature, or engine RPM displays going blank or freezing)
• Reduced engine power or derate mode activation as a protective measure when the ECM cannot verify system parameters
• Hydraulic system irregularities, including delayed response or inconsistent swing/boom speed due to control module miscommunication
• Inability to access diagnostic information through the monitor panel or external diagnostic tools

Potential Causes

• Damaged or corroded CAN bus wiring harness, particularly at flex points near the engine compartment, swing bearing, or cab mounting areas where vibration and movement cause wire chafing
• Loose or corroded connector pins at ECM, hydraulic controller, or monitor panel connections—common in used machines exposed to moisture and dirt infiltration
• Failed termination resistors within the CAN network, causing signal reflection and data corruption
• ECM or controller module failure, often due to voltage spikes, water intrusion, or age-related component degradation in older excavators
• Aftermarket component interference from improperly installed accessories that create electrical noise on the CAN bus
• Battery voltage issues or poor grounding causing insufficient power supply to control modules

How to Troubleshoot and Fix Code AB00KE

Step 1: Visual Inspection and Connector Check Begin by inspecting all CAN bus harness connectors at the ECM (located behind the operator's cab), hydraulic controller (near the main control valve), and monitor panel. Look for bent pins, green corrosion, or moisture inside connectors. On used PC850-8Rs, pay special attention to harness routing near the swing bearing where cable flexing causes insulation wear. Clean connectors with electrical contact cleaner and apply dielectric grease to prevent future corrosion.

Step 2: CAN Bus Continuity and Resistance Testing Using a digital multimeter, measure resistance between CAN-High and CAN-Low terminals at the ECM connector (with harness disconnected). You should read approximately 60 ohms, indicating proper termination resistors are present. Check continuity along the entire harness length, testing at multiple connection points. Infinite resistance or readings below 50 ohms suggest open circuits or shorted wiring.

Step 3: Voltage and Signal Quality Verification With the ignition on (engine off), measure voltage on the CAN-High line (should read approximately 2.5-3.5V) and CAN-Low line (approximately 1.5-2.5V). Connect Komatsu KOMTRAX diagnostic software or a compatible CAN bus analyzer to monitor real-time data traffic. Look for missing messages, excessive error frames, or communication dropouts that pinpoint which module is failing to transmit.

Step 4: Module and Ground Testing Verify all ground connections at each control module are clean, tight, and show less than 0.5 ohms resistance to chassis ground. For used excavators, ground straps often corrode internally despite appearing intact externally. If wiring and grounds test properly, suspect ECM or controller failure—swap modules with known-good units if available, or send for professional testing and repair.

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Disclaimer: This guide provides general troubleshooting information for experienced diesel mechanics and equipment owners. 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 damage or safety hazards.