What is Komatsu PC220-10 Fault Code DXE6KB?

Fault Code DXE6KB indicates a communication error between the Engine Control Module (ECM) and the DEF (Diesel Exhaust Fluid) dosing control unit in the Selective Catalytic Reduction (SCR) system. This code specifically triggers when the ECM cannot establish or maintain proper CAN bus communication with the DEF injection system, which is critical for meeting Tier 4 Final emissions standards on the Komatsu PC220-10.

This fault is particularly significant because the PC220-10's SCR aftertreatment system relies on continuous data exchange between the ECM and DEF dosing module to properly inject urea into the exhaust stream. Without this communication, the machine cannot maintain emissions compliance, and Komatsu's programming will typically initiate a derate mode after a specified time period to protect the system and ensure regulatory compliance.

Common Symptoms

• DEF system warning light illuminated on the monitor panel, often accompanied by an audible alarm
• Engine power derate to approximately 50-70% after initial warning period (usually after 50-100 operating hours)
• Error message on display screen specifically referencing SCR or DEF system malfunction
• Increased exhaust temperatures due to improper DEF injection timing or complete injection failure
• Machine may enter limp mode preventing operation above idle in severe cases

Potential Causes

The DXE6KB code in used PC220-10 excavators typically stems from several age-related issues. The most common cause is corroded or damaged wiring harness connectors at the DEF dosing control unit, particularly where the harness runs along the frame rail near the fuel tank—a known rub point on this model.

Failed DEF dosing control unit itself ranks as the second most frequent culprit, especially in machines with over 5,000 hours. The CAN bus termination resistor failure within either the ECM or dosing module can also interrupt communication.

Additional causes include water intrusion into connectors (common in machines stored outdoors), damaged CAN bus wiring between the ECM and DEF system, and occasionally, ECM software corruption requiring reflashing.

How to Troubleshoot and Fix Code DXE6KB

Step 1: Visual Inspection Begin by thoroughly inspecting the DEF dosing unit wiring harness from the ECM to the dosing control module. Check for chafed wires, corroded connectors, or loose pins at both the dosing unit (located near the DEF tank) and ECM connections. Pay special attention to harness routing along the right-side frame rail where contact with brackets frequently causes wear in used machines.

Step 2: Check CAN Bus Communication Using Komatsu KOMTRAX diagnostic software or a compatible CAN bus scanner, verify communication integrity. Measure CAN High and CAN Low voltage at the DEF dosing module connector—you should see approximately 2.5V on each line with ignition on. Check termination resistance between CAN High and CAN Low pins; it should read approximately 60 ohms with the system powered off.

Step 3: Component Testing Disconnect the DEF dosing control unit connector and inspect for corrosion or moisture. Test the module's power supply: verify 12V battery voltage at the power pin and proper ground continuity (less than 0.5 ohms resistance). If wiring checks good, the dosing control unit likely requires replacement—a common failure point after 6,000+ hours.

Step 4: Verify Repair After addressing identified issues, clear the fault code using diagnostic software and operate the machine through multiple regeneration cycles to confirm proper SCR system communication. Monitor for code recurrence over several hours of operation.

For used excavators, always clean connector terminals with electrical contact cleaner and apply dielectric grease before reconnection to prevent future corrosion issues.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu PC220-10 service manual and consider professional technician assistance for complex electrical diagnostics or if you're uncomfortable working with emissions control systems.