What is Komatsu PC210-10 Fault Code DR21KX?

Fault Code DR21KX on the Komatsu PC210-10 excavator indicates a communication error between the Engine Controller (ECM) and the Machine Controller (MCM) via the CAN Bus network. This code specifically signals that the ECM is not receiving proper data packets from the MCM or detecting inconsistent signal timing on the Controller Area Network.

The CAN Bus system is the digital nervous system of modern Komatsu excavators, allowing multiple controllers to share critical operational data. When communication breaks down between the ECM (managing engine performance) and MCM (controlling hydraulics, display, and machine functions), the excavator cannot properly coordinate power delivery with hydraulic demand. This fault is particularly critical on the PC210-10 because the integrated control system relies on constant communication to optimize fuel efficiency and prevent component damage during high-load operations.

Common Symptoms

• Warning lights: The engine malfunction lamp and/or action indicator illuminate on the monitor panel
• Derated performance: Engine power may be automatically reduced to 70-80% capacity as a protective measure
• Intermittent loss of display data: Monitor may show dashes or zeros for engine RPM, coolant temperature, or fuel level
• Erratic hydraulic response: Inconsistent or sluggish boom/bucket movements due to improper power-to-load matching
• Possible starting issues: Machine may experience delayed cranking or require multiple key cycles to start

Potential Causes

On used Komatsu PC210-10 excavators, this fault typically stems from:

• CAN Bus wiring harness damage: Rubbing or chafing at known wear points near the engine mounting area or cab base where harnesses flex during machine operation
• Corroded or moisture-contaminated connectors: The 120-ohm termination resistor connections at either the ECM or MCM often develop corrosion in high-humidity environments
• Failing ECM or MCM: Control modules develop internal faults after 8,000+ operating hours, particularly if exposed to excessive vibration
• Voltage irregularities: Weak batteries (below 12.2V) or failing alternators causing voltage drops during high electrical loads
• Aftermarket component interference: Non-OEM monitors, radios, or telematics devices improperly tapped into the CAN network

How to Troubleshoot and Fix Code DR21KX

Step 1: Visual Inspection and Connection Check Begin by inspecting the CAN Bus harness routing from the ECM (located behind the right-hand service door) to the MCM (under the operator seat). Look specifically for harness damage at the engine-to-frame transition point and where cables pass through the cab mounting bracket. Disconnect and inspect the 9-pin Deutsch connectors at both controllers—clean any visible corrosion with electrical contact cleaner and apply dielectric grease before reconnecting.

Step 2: Electrical Testing with Diagnostic Tools Using a digital multimeter, measure resistance between CAN-H and CAN-L terminals at the ECM connector (typically pins 6 and 14 on Komatsu systems). You should read approximately 60 ohms with the key off—this indicates proper termination resistors. Next, connect Komatsu KOMTRAX or PC diagnostic software to read real-time CAN Bus traffic and identify if one controller is failing to transmit.

Step 3: Voltage Supply Verification Check battery voltage at both the ECM and MCM power supply pins with the key on, engine off—readings should be 12.5-14.5V. Perform a voltage drop test on ground circuits by measuring between controller ground pins and battery negative while cranking (should be under 0.2V). For used excavators, pay special attention to ground strap connections at the engine block and frame, as corrosion here commonly causes intermittent communication faults.

Step 4: Component Isolation and Replacement If wiring and voltage tests pass, disconnect all non-essential devices from the CAN network (aftermarket displays, GPS trackers). Clear the code and operate for one hour. If DR21KX returns, replace the 120-ohm termination resistors (Komatsu part #21W-06-22360) before considering controller replacement, as these inexpensive components fail more frequently than ECMs in high-vibration applications.

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Disclaimer: This guide provides general troubleshooting steps for Komatsu PC210-10 fault code DR21KX. Excavator electrical systems involve complex diagnostics that may require manufacturer-specific tools and training. Always consult a certified Komatsu technician or authorized service center for definitive diagnosis, especially before replacing expensive components like controllers. Improper repairs may void remaining warranties on used equipment.