Komatsu PC850-8R Fault Code DA2SKQ: Complete Diagnostic Guide

What is Komatsu PC850-8R Fault Code DA2SKQ?

Fault Code DA2SKQ indicates a communication error or data anomaly within the Komatsu PC850-8R's machine control network, specifically affecting the CAN bus system that connects the Engine Control Module (ECM), hydraulic controllers, and monitoring systems.

This code typically signals that one or more control modules are experiencing intermittent or complete loss of communication across the Controller Area Network (CAN). The PC850-8R relies heavily on real-time data exchange between its ECM, pump controller, and monitor panel to optimize hydraulic performance and engine efficiency. When this communication breaks down, the machine's integrated control system cannot function properly, potentially leading to reduced performance or complete operational shutdown. For used excavators, this fault often stems from age-related deterioration of electrical components rather than catastrophic system failures.

Common Symptoms

When DA2SKQ is active on your PC850-8R, operators typically experience:

• Multiple warning lights illuminating simultaneously on the monitor panel, including check engine and system malfunction indicators
• Erratic hydraulic response or unexpected power derate modes, with the machine entering limp mode or reduced output
• Intermittent loss of monitor display functions, including gauge readings, backup camera, or operational data
• Engine performance inconsistencies, such as irregular RPM fluctuations or failure to reach full throttle
• Stored multiple fault codes appearing together, indicating widespread communication disruption across control modules

Potential Causes

The most common technical causes for DA2SKQ on used PC850-8R excavators include:

• CAN bus wiring harness damage at known rub points near the swing bearing, engine compartment firewall, or along the boom base where cables experience constant flexing
• Corroded or moisture-contaminated connectors on the main harness, particularly the 120-pin ECM connector and hydraulic controller connections
• Failed termination resistors (120-ohm) at either end of the CAN bus network, causing signal reflection and data corruption
• Faulty ECM or pump controller modules with internal communication circuit failures, more common in machines exceeding 8,000 operating hours
• Low battery voltage or poor ground connections affecting the entire electrical system's ability to maintain stable CAN bus voltage (nominal 2.5V differential)
• Aftermarket component interference, including non-OEM monitors or telematics devices improperly integrated into the CAN network

How to Troubleshoot and Fix Code DA2SKQ

Step 1: Initial System Verification Connect Komatsu KOMTRAX Plus diagnostic software or a compatible CAN bus scanner to the diagnostic port. Record all active and stored codes. Check battery voltage (should be 24-28V with engine running) and inspect all main ground straps between engine, frame, and cab for corrosion or looseness.

Step 2: Physical Harness Inspection Perform a thorough visual inspection of the main wiring harness, focusing on areas where cables route through the swing bearing, near hydraulic lines, and around the engine. Look for abraded insulation, pinched wires, or evidence of rodent damage. On used excavators, pay special attention to connector seals—remove and inspect the ECM connector and hydraulic controller connectors for green corrosion or moisture intrusion.

Step 3: CAN Bus Electrical Testing Using a digital multimeter, measure resistance between CAN-High and CAN-Low terminals at the ECM connector with all modules disconnected—you should read approximately 60 ohms (two 120-ohm termination resistors in parallel). Test each termination resistor individually; replace if readings deviate by more than 10%. With the system powered, measure CAN bus voltage: CAN-High should read 3.5V and CAN-Low 1.5V at idle (2.0V differential).

Step 4: Module Isolation Testing Systematically disconnect individual control modules while monitoring for code clearance. This identifies whether a specific controller is corrupting the network. For used machines, the pump controller and monitor panel are common failure points. If isolating a module clears DA2SKQ, that component requires replacement or repair.

Step 5: Repair and Verification Replace damaged harness sections using OEM-spec shielded CAN cable, ensuring proper crimping and sealing of all connections. Apply dielectric grease to all reconnected plugs. Clear all codes, perform a complete machine function test, and monitor for code recurrence over several operating hours. For persistent issues on high-hour machines, ECM reflashing or replacement may be necessary.

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Disclaimer: This guide provides general diagnostic information for the Komatsu PC850-8R. CAN bus systems are complex and require proper diagnostic equipment. Always consult the official Komatsu service manual and consider professional assistance from certified Komatsu technicians for definitive diagnosis and repair, especially when dealing with critical control system components.