Komatsu PC650-8R Fault Code E10CA757: Complete Diagnostic Guide

What is Komatsu PC650-8R Fault Code E10CA757?

Fault Code E10CA757 indicates a communication error or data transmission failure between the engine controller (ECM) and the hydraulic system controller on the Komatsu PC650-8R excavator. This code specifically relates to the CAN (Controller Area Network) bus communication protocol that allows critical machine systems to exchange operational data in real-time.

The PC650-8R relies on seamless communication between its SAA6D140E-7 engine ECM and the hydraulic controller to optimize fuel efficiency, power delivery, and hydraulic response. When this communication link fails, the machine cannot properly coordinate engine output with hydraulic demand, leading to reduced performance and potential safety concerns. This fault is particularly critical in used excavators where connector corrosion and harness wear are common culprits.

Common Symptoms

When Code E10CA757 is active, operators typically experience:

• Warning light illumination on the monitor panel, often accompanied by a communication error message
• Reduced engine power or derate mode, limiting maximum RPM to protect the machine
• Sluggish hydraulic response or inconsistent boom/arm movements due to improper load-sensing coordination
• Intermittent loss of monitor display data, including fuel consumption, hydraulic temperature, or system pressures
• Engine may run rough or fail to respond properly to throttle inputs during combined operations

Potential Causes

The most common technical causes for E10CA757 on used PC650-8R excavators include:

• Corroded or damaged CAN bus connectors at the ECM, hydraulic controller, or junction points (especially C201 and C301 connectors in the engine compartment)
• Harness chafing or wire breaks along known rub points near the swing bearing or along the main chassis harness
• Failed termination resistors on the CAN network (typically 120-ohm resistors at network endpoints)
• ECM or hydraulic controller internal failure, though less common than wiring issues
• Voltage supply problems to either controller, often caused by corroded ground connections (G101, G102)
• Water intrusion into controller housings from damaged seals or improper storage

How to Troubleshoot and Fix Code E10CA757

Step 1: Visual Inspection Begin with a thorough inspection of all CAN bus harness connectors between the engine ECM (located behind the operator cab) and the hydraulic controller (mounted near the hydraulic pump). Look specifically for green corrosion, bent pins, or moisture inside connectors. On used machines, check harness routing near the swing bearing where vibration causes wear.

Step 2: Electrical Testing Using a digital multimeter, verify CAN-High and CAN-Low voltage levels at both controllers. With ignition on, you should measure approximately 2.5V on CAN-High and 2.5V on CAN-Low at rest. Check termination resistance by measuring between CAN-High and CAN-Low with power off—you should read approximately 60 ohms (two 120-ohm resistors in parallel).

Step 3: Diagnostic Software Analysis Connect Komatsu KOMTRAX or compatible diagnostic software to access live data streams. Monitor communication status between controllers while wiggling harnesses to identify intermittent connections. Check for voltage drops below 9V during cranking, which can cause communication failures.

Step 4: Component Replacement If testing reveals faulty connectors, clean with electrical contact cleaner and apply dielectric grease before reconnection. Replace damaged harness sections using OEM-spec shielded CAN cable. For used excavators, always inspect ground points G101 and G102 for corrosion and re-establish clean metal-to-metal contact before replacing expensive controllers.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number and consider professional diagnostic assistance for complex electrical issues.