Komatsu PC650LC-8R Fault Code AA10NX: Complete Diagnostic Guide

What is Komatsu PC650LC-8R Fault Code AA10NX?

Fault Code AA10NX indicates a communication error or data transmission failure within the Komatsu PC650LC-8R's CAN (Controller Area Network) bus system, specifically affecting the machine's main controller network.

This diagnostic trouble code (DTC) signals that the Engine Control Module (ECM) or Machine Controller has detected an interruption or abnormal signal pattern on the CAN communication line. The CAN bus is the critical digital nervous system that allows various electronic control units—including the engine controller, hydraulic controller, and monitor panel—to exchange real-time operational data. When this communication breaks down, the excavator's integrated systems cannot coordinate properly, potentially affecting performance, safety features, and diagnostic capabilities.

For the PC650LC-8R's advanced Tier 4 Final emissions system and sophisticated hydraulic management, reliable CAN communication is essential for optimal fuel efficiency and coordinated machine response.

Common Symptoms

• Warning lights illuminated on the monitor panel, often including a general malfunction indicator or communication error icon
• Intermittent or complete loss of monitor display functions, including gauge readings, temperature displays, or hour meter
• Reduced engine power or activation of derate mode as a protective measure when controllers cannot verify operating parameters
• Erratic hydraulic response or loss of fine control features due to disrupted communication between hydraulic and engine controllers
• Multiple simultaneous fault codes appearing as various controllers report communication failures with each other

Potential Causes

Damaged or corroded CAN bus wiring harness is the most common culprit in used excavators, particularly where harnesses route near moving components or through the swing bearing area where flexing causes wire fatigue.

Loose or corroded connector pins at the ECM, machine controller, or junction boxes—especially problematic in machines exposed to moisture or operating in coastal/high-humidity environments.

Failed termination resistors at either end of the CAN bus network, which are essential for proper signal integrity and preventing electrical reflections.

ECM or controller module failure, though less common, can occur in high-hour machines or those that experienced electrical surges or water intrusion.

Aftermarket accessory installations that improperly tap into the CAN network, creating signal interference or improper loading on the communication lines.

How to Troubleshoot and Fix Code AA10NX

Step 1: Visual Inspection of Harnesses and Connectors

Begin by thoroughly inspecting all CAN bus wiring harnesses, paying special attention to routing through the swing bearing area, along the boom, and near the engine compartment. Look for abraded insulation, pinched wires, or signs of harness movement against metal surfaces. On used excavators, check for previous repair attempts using electrical tape, which often indicates underlying damage. Disconnect and inspect all CAN network connectors for bent pins, green corrosion, or moisture intrusion.

Step 2: Resistance and Continuity Testing

Using a digital multimeter, measure the resistance between the CAN-High and CAN-Low lines at the ECM connector with all power off and connectors separated. You should read approximately 60 ohms, indicating both 120-ohm termination resistors are present and functioning in parallel. Test continuity of individual CAN-High and CAN-Low wires from the ECM through to the machine controller and monitor, checking for opens or shorts to ground.

Step 3: Diagnostic Software Analysis

Connect Komatsu KOMTRAX or compatible diagnostic software to access detailed communication logs. Monitor real-time CAN bus traffic to identify which specific controller is dropping offline or transmitting corrupted data. Check voltage levels on CAN-High (should be approximately 3.5V) and CAN-Low (approximately 1.5V) during operation—significant deviation indicates power supply issues or network loading problems.

Step 4: Component Isolation and Replacement

If wiring tests pass, systematically disconnect non-essential CAN devices (aftermarket monitors, telematics units) to isolate potential interference sources. Replace any corroded connectors with OEM Komatsu weatherproof connectors rather than generic alternatives. For used machines with high hours, consider replacing the entire engine-to-cab harness if multiple wear points are evident, as this prevents recurring failures.

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Disclaimer: This guide provides general diagnostic information for experienced technicians. Always consult the official Komatsu service manual for your specific machine serial number and consider professional diagnostic services for complex electrical issues. Improper troubleshooting can cause additional damage to electronic control systems.