Komatsu PC850-8R Fault Code E10CA757: Complete Diagnostic Guide

What is Komatsu PC850-8R Fault Code E10CA757?

Fault Code E10CA757 indicates a communication error or data transmission failure within the machine's CAN (Controller Area Network) bus system, specifically related to abnormal signal detection between the engine controller (ECM) and hydraulic system controllers.

This diagnostic trouble code (DTC) signals that the ECM has detected inconsistent or missing data packets from one or more control modules on the network. The PC850-8R relies on continuous communication between its engine control unit, hydraulic controller, and monitor panel to optimize performance and fuel efficiency. When this communication breaks down, the machine's integrated systems cannot coordinate properly, leading to reduced operational capability and potential safety concerns.

For this 85-ton class excavator, maintaining proper CAN bus integrity is critical because the machine's advanced load-sensing hydraulics and engine management depend on real-time data exchange to prevent component damage and maximize productivity.

Common Symptoms

• Warning lights illuminated on the monitor panel, specifically communication or system error indicators
• Reduced engine power or automatic derate mode activation, limiting machine performance to protect components
• Erratic hydraulic response including delayed or inconsistent boom, arm, or bucket movements
• Intermittent gauge readings or complete loss of display information on the operator monitor
• Engine may enter limp mode or fail to start in severe cases of communication failure

Potential Causes

The E10CA757 code typically results from these technical issues common in used excavators:

• Damaged or corroded CAN bus wiring harness, particularly at flex points near the swing bearing or along the boom where cables experience constant movement
• Loose or oxidized connector pins at the ECM, hydraulic controller, or junction boxes due to moisture intrusion
• Failed termination resistors on the CAN network (typically 120-ohm resistors at network endpoints)
• ECM or controller module failure, though less common than wiring issues in used machines
• Voltage irregularities from failing batteries or alternator problems affecting network stability
• Physical damage to harnesses from previous repairs, rodent activity, or rubbing against frame components

How to Troubleshoot and Fix Code E10CA757

Step 1: Visual Inspection Begin with a thorough physical examination of all wiring harnesses along the main frame, particularly where cables route through the swing bearing area and along the upper structure. Look for abraded insulation, pinched wires, or evidence of previous repairs. On used excavators, check for corrosion buildup on all CAN bus connectors—the 9-pin Deutsch connectors are particularly vulnerable to moisture intrusion.

Step 2: Electrical Testing Using a digital multimeter, verify CAN-High and CAN-Low voltage levels at the ECM connector. With ignition on and engine off, you should measure approximately 2.5V on both lines at rest. Check for proper termination resistance by measuring between CAN-H and CAN-L pins with all controllers disconnected—you should read approximately 60 ohms (two 120-ohm resistors in parallel). Deviations indicate open circuits or missing terminators.

Step 3: Diagnostic Software Analysis Connect Komatsu KOMTRAX or compatible diagnostic software to access detailed fault data. Check freeze frame data to identify which specific controller lost communication. Monitor live data while wiggling harnesses to identify intermittent connections—a common issue in machines with high operating hours.

Step 4: Component-Level Diagnosis If wiring tests pass, individually disconnect controllers to isolate the faulty module. For used machines, inspect connector backshells for cracks and apply dielectric grease to all cleaned connections before reassembly. Replace any harness sections showing wear at known rub points rather than attempting tape repairs.

Critical for Used Equipment: Before replacing expensive controllers, always address harness wear, connector corrosion, and grounding issues first—these account for over 80% of CAN bus faults in high-hour excavators.

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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 diagnosis for complex electrical issues. Improper repairs to CAN bus systems can cause additional controller damage.