Komatsu PC750-7 Fault Code AA10NX: Complete Diagnostic Guide

What is Komatsu PC750-7 Fault Code AA10NX?

Fault Code AA10NX indicates a communication error or abnormal signal detected in the machine's network system, specifically related to the CAN (Controller Area Network) bus communication between the engine controller and other electronic control modules.

This code typically appears when the ECM (Engine Control Module) cannot properly communicate with peripheral controllers such as the hydraulic control unit, monitor panel, or transmission controller. For the PC750-7, which relies heavily on integrated electronic systems for optimal performance, this communication breakdown can significantly impact machine functionality and operational efficiency. The CAN bus serves as the central nervous system of modern excavators, making this fault critical to address immediately.

Common Symptoms

When Code AA10NX is active, operators typically experience:

• Warning lights illuminated on the monitor panel, often accompanied by error messages or blank display sections
• Intermittent loss of gauge readings including engine RPM, hydraulic temperature, or fuel level displays
• Reduced engine power or activation of derate mode as a protective measure
• Erratic hydraulic response or delayed control inputs due to communication lag
• Multiple fault codes appearing simultaneously across different systems

Potential Causes

The most common technical causes for AA10NX in used PC750-7 excavators include:

• Corroded or damaged CAN bus connectors, particularly at the main harness junction behind the cab (known wear point on this model)
• Frayed or pinched wiring in the engine compartment where harnesses route near the turbocharger or hydraulic lines
• Failed termination resistors at either end of the CAN network (120-ohm resistors)
• ECM or controller module failure due to moisture intrusion or age-related component degradation
• Low battery voltage or poor ground connections affecting network stability
• Aftermarket component interference from non-OEM monitors or accessories improperly integrated into the CAN system

How to Troubleshoot and Fix Code AA10NX

Step 1: Visual Inspection Begin by thoroughly inspecting all wiring harnesses along the CAN bus network. On used excavators, focus on areas where harnesses contact metal surfaces or experience vibration. Check the main connector blocks behind the operator's seat and near the ECM mounting location for corrosion, bent pins, or moisture.

Step 2: Electrical Testing Using a digital multimeter, measure CAN-High and CAN-Low voltage at the diagnostic connector. You should read approximately 2.5V on each line with the key on, engine off. Check termination resistance between CAN-High and CAN-Low—it should read approximately 60 ohms (two 120-ohm resistors in parallel). Any significant deviation indicates a wiring fault or missing terminator.

Step 3: Advanced Diagnostics Connect Komatsu KOMTRAX diagnostic software or compatible scan tool to monitor real-time CAN bus traffic. Identify which specific controller is dropping communication. Test battery voltage (should be 24V minimum) and verify all ground connections are clean and tight, especially the ECM ground strap.

Step 4: Component Replacement If diagnostics isolate a specific failed controller or damaged harness section, replace only the affected component. For used machines, always apply dielectric grease to connectors during reassembly to prevent future corrosion.

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Disclaimer: This guide provides general troubleshooting information. Always consult Komatsu service manuals and consider professional diagnostic services for complex electrical issues, especially when working with high-value used equipment.