Komatsu PC850SE-8R Fault Code DGH2KB: Complete Diagnostic Guide

What is Komatsu PC850SE-8R Fault Code DGH2KB?

Fault Code DGH2KB indicates a communication error or data transmission failure within the machine's CAN (Controller Area Network) bus system, specifically affecting the integration between the engine ECM (Engine Control Module) and the hydraulic control system.

This code typically signals that critical operational data is not being properly exchanged between control modules. For the PC850SE-8R, this is particularly serious because the machine relies on precise coordination between engine output and hydraulic demand to maintain optimal performance and fuel efficiency. When this communication pathway fails, the excavator's integrated control system cannot properly manage power distribution, potentially leading to reduced productivity and component stress.

Common Symptoms

When DGH2KB is active, operators typically experience:

• Warning lights illuminated on the monitor panel, often accompanied by a communication error message
• Reduced engine power or automatic derate mode, limiting machine performance to protect components
• Erratic hydraulic response, including inconsistent swing speed or boom/arm movements
• Intermittent loss of monitor display functions, with gauges or readouts becoming unresponsive
• Difficulty starting or unexpected engine shutdown in severe cases

Potential Causes

The most common technical causes for DGH2KB on used PC850SE-8R excavators include:

• CAN bus wiring harness damage from rubbing against frame components, particularly near the engine bay and swing bearing area
• Corroded or loose connector pins at the ECM or hydraulic controller connection points
• Failed termination resistors within the CAN network causing signal reflection
• ECM or hydraulic controller internal failure, more common in high-hour machines
• Voltage irregularities from aging batteries or failing alternators affecting module communication
• Water intrusion into sealed connectors, especially on machines operated in wet conditions

How to Troubleshoot and Fix Code DGH2KB

Step 1: Visual Inspection Begin by thoroughly inspecting all wiring harnesses between the engine ECM and hydraulic control module. On used excavators, check for harness wear at known friction points near the swing motor and along the main frame rails. Examine all connector pins for corrosion, bent terminals, or moisture intrusion.

Step 2: Electrical Testing Using a digital multimeter, verify proper voltage supply (typically 24V) at both the ECM and hydraulic controller. Check CAN-High and CAN-Low wire resistance between modules—readings should show approximately 60 ohms with the system powered off, indicating proper termination. Use Komatsu KOMTRAX diagnostic software or compatible scan tools to monitor real-time CAN bus traffic and identify which module is failing to communicate.

Step 3: Component Testing Test termination resistors at each end of the CAN network (typically 120 ohms each). If voltage and resistance values are correct but the code persists, perform a wiggle test on harnesses while monitoring live data to identify intermittent connections. For used machines with over 8,000 hours, consider the possibility of internal ECM failure requiring module replacement or professional reprogramming.

Critical Note for Used Equipment: Before replacing expensive modules, always address harness wear, connector corrosion, and grounding issues first—these account for approximately 70% of communication faults in older excavators.

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Disclaimer: This guide provides general diagnostic information. Always consult Komatsu service manuals and qualified technicians for complex electrical repairs. Improper diagnosis may cause additional damage or safety hazards.