What is Komatsu PC220-8M0 Fault Code DAF8KB?

Fault Code DAF8KB on the Komatsu PC220-8M0 indicates a communication error between the machine's Engine Control Module (ECM) and the Hydraulic Control Module (HCM), specifically related to CAN bus network failure or data transmission interruption.

This fault code is part of Komatsu's advanced electronic diagnostic system that monitors real-time communication between critical control systems. The CAN (Controller Area Network) bus serves as the central nervous system for the PC220-8M0, allowing the engine controller and hydraulic systems to share operational data continuously. When this communication pathway fails or becomes degraded, the excavator cannot properly coordinate engine power delivery with hydraulic demand, leading to performance issues and potential safety concerns. For this model specifically, the integrated KOMTRAX telematics system relies heavily on uninterrupted CAN bus communication, making this fault particularly critical for fleet management and diagnostic monitoring.

Common Symptoms

• Yellow warning light illuminated on the instrument cluster, often accompanied by reduced hydraulic response or sluggish boom/arm movements
• Engine derate mode activation, limiting RPM to approximately 1,500-1,800 range to protect systems during communication failure
• Intermittent loss of gauge functions, including fuel level, temperature readings, or hydraulic oil temperature displays becoming erratic or blank
• Error messages displaying on the monitor panel indicating "System Communication Error" or similar CAN-related alerts
• Hydraulic pumps failing to adjust output pressure appropriately for work conditions, resulting in inconsistent digging force

Potential Causes

The most common causes for DAF8KB on used PC220-8M0 excavators include:

• Corroded or damaged CAN bus connectors, particularly at the ECM harness connection points behind the operator cab where moisture intrusion is common
• Wiring harness chafing along the main frame near the turntable, where repeated rotation causes insulation wear on CAN high/low signal wires
• Failed terminating resistors (120-ohm) at either end of the CAN bus network, often degraded in machines with 5,000+ operating hours
• ECM or HCM internal communication module failure, more prevalent in excavators operating in high-vibration or extreme temperature environments
• Voltage supply issues to either control module, typically from corroded ground connections or failing main power relay
• Aftermarket component interference, especially non-OEM telematics devices improperly spliced into the CAN network

How to Troubleshoot and Fix Code DAF8KB

Step 1: Initial Visual Inspection Begin by inspecting all wiring harnesses running between the ECM (located near the battery box) and the HCM (mounted near the hydraulic pumps). Look specifically for visible damage, chafing, or corrosion on connectors. On used excavators, pay special attention to harness routing near the swing bearing where repeated motion causes wear. Check all connector pins for corrosion, bent contacts, or moisture contamination—clean with electrical contact cleaner if necessary.

Step 2: CAN Bus Network Testing Using a digital multimeter, measure the resistance between CAN High and CAN Low terminals with all modules connected and ignition off. You should read approximately 60 ohms, indicating both 120-ohm terminating resistors are present and functional. Then disconnect modules one at a time to isolate which terminating resistor may have failed. With ignition on and engine running, use a Komatsu-specific diagnostic tool (such as KTEC or VCADS) to monitor live CAN bus traffic and identify which module is failing to communicate.

Step 3: Voltage and Ground Verification Verify that both the ECM and HCM are receiving proper supply voltage (typically 24V DC on this model). Check voltage at each module's power supply pin while cranking the engine—voltage should not drop below 22V. Equally important, test ground circuit integrity by measuring resistance between each module's ground pin and battery negative terminal; readings above 0.5 ohms indicate poor ground connections requiring cleaning or repair.

Step 4: Component Replacement Protocol If wiring and connections test satisfactory, the fault typically resides within one of the control modules. Before replacing expensive components on used equipment, consider swapping modules with a known-good unit to confirm diagnosis. Replace failed terminating resistors first (low cost, high failure rate), then address module replacement. Always clear fault codes using diagnostic software after repairs and perform a complete functional test under load conditions.

For used excavators specifically: Check service history for previous electrical repairs—improperly repaired harnesses often develop intermittent faults. Inspect aftermarket accessories that may have been installed, as improper CAN bus taps are a frequent cause of communication errors in second-hand machines.

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Disclaimer: This guide provides general diagnostic information for experienced technicians. Always consult the official Komatsu service manual for your specific machine serial number and consider professional diagnostic assistance for complex electrical issues. Improper troubleshooting can result in further damage to electronic control systems.