Komatsu PC210LC-10 Fault Code 879AKA: Complete Diagnostic Guide

What is Komatsu PC210LC-10 Fault Code 879AKA?

Fault Code 879AKA indicates a communication error or abnormal signal from the engine controller (ECM) to the machine controller on the Komatsu PC210LC-10 excavator. This code specifically points to a breakdown in the CAN bus communication network between the engine's electronic control module and the machine's main monitoring system.

This fault is critical because the PC210LC-10 relies on constant data exchange between controllers to regulate engine performance, hydraulic functions, and safety systems. When communication fails, the machine may enter derate mode or experience reduced operational capability to protect critical components. The CAN (Controller Area Network) system is the digital backbone of modern Komatsu excavators, making this fault a priority concern for used equipment owners.

Common Symptoms

• Warning light illumination on the dashboard, typically showing engine or system malfunction indicators
• Loss of monitor display data, with blank screens or frozen readings on the cab panel
• Engine power reduction (derate mode), limiting RPM to approximately 1500-1800 to prevent potential damage
• Intermittent gauge operation, where tachometer, temperature, or pressure readings fluctuate or disappear
• Hydraulic response changes, as the machine controller cannot properly coordinate engine load with hydraulic demand

Potential Causes

On used PC210LC-10 excavators, this code commonly stems from:

• Corroded or damaged CAN bus connectors, especially at harness junction points near the engine firewall
• Wiring harness chafing where cables route along the engine compartment frame rails (known wear point on this model)
• Failed termination resistors within the CAN network, typically located at the ECM or machine controller
• ECM or machine controller internal failures, often caused by moisture intrusion in older machines
• Voltage supply issues from the main power harness, creating intermittent power to controllers
• Aftermarket component interference, particularly non-OEM monitoring systems that disrupt CAN signals

How to Troubleshoot and Fix Code 879AKA

Step 1: Visual Inspection of Harness and Connectors Begin by inspecting the main wiring harness routing from the engine ECM (located passenger side of engine block) to the machine controller (under operator cab floor). On used machines, check for visible harness rubbing against frame members, heat damage near exhaust components, or oil contamination. Disconnect and inspect all CAN bus connectors (typically green or yellow-coded) for corrosion, bent pins, or moisture.

Step 2: Test CAN Bus Communication Signals Using a digital multimeter, measure resistance between CAN High and CAN Low terminals at the ECM connector (consult service manual for pin identification). You should read approximately 60 ohms with ignition off, indicating proper termination resistors. With ignition on, use a Komatsu diagnostic laptop running KOMTRAX Plus software to monitor real-time communication status between controllers.

Step 3: Verify Power Supply and Grounds Check battery voltage at both ECM and machine controller (should be 24-28V with engine running). Inspect all ground connections, particularly the engine-to-frame ground strap and controller chassis grounds—common failure points on excavators with 5,000+ hours.

Step 4: Component Isolation Testing If harness and power checks pass, disconnect non-essential devices from the CAN network one at a time (aftermarket monitors, telematics devices) to identify potential interference sources. Replace any termination resistors showing readings outside 55-65 ohms.

For used excavators, always prioritize connector cleaning and harness repairs before replacing expensive controllers, as environmental wear accounts for 70% of communication faults.

---

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.