What is Komatsu PC220-8M0 Fault Code DW91KA?

Fault Code DW91KA on the Komatsu PC220-8M0 indicates a communication error between the machine's main controller (KOMTRAX telematics system) and the engine ECM (Engine Control Module), or a data transmission failure within the CAN bus network. This diagnostic trouble code specifically signals that the onboard monitoring system has detected an intermittent or complete loss of communication with critical control modules.

This fault is particularly important for the PC220-8M0 because this model relies on integrated communication between the engine ECM, hydraulic controller, and KOMTRAX system to optimize fuel efficiency and performance. When communication breaks down, the machine may enter a protective derate mode or display erratic behavior, directly impacting productivity and potentially causing expensive downtime on used equipment where wiring harnesses may have deteriorated.

Common Symptoms

• Warning light illumination on the instrument cluster, often accompanied by a displayed fault code on the monitor panel
• Reduced engine power or derate mode activation, limiting machine performance to protect components
• Intermittent loss of dashboard display information, including fuel readings, hydraulic temperature, or operational hours
• KOMTRAX data upload failures, preventing remote monitoring and fleet management capabilities
• Erratic hydraulic response or unresponsive auxiliary functions due to incomplete control signals

Potential Causes

The most common technical causes for DW91KA on used Komatsu PC220-8M0 excavators include:

• Damaged or corroded CAN bus wiring harness, especially at known rub points near the engine compartment and swing bearing
• Failed or intermittent main controller connections where vibration has loosened harness plugs over operational hours
• Corroded connector pins at the ECM or KOMTRAX control unit, typical in machines exposed to moisture or harsh environments
• Faulty KOMTRAX communication module requiring replacement or software update
• ECM software corruption or outdated firmware lacking compatibility updates
• Physical damage to shielded CAN bus cables from rodents, maintenance work, or component replacement

How to Troubleshoot and Fix Code DW91KA

Step 1: Visual Inspection of Wiring Harness Begin by thoroughly inspecting all CAN bus wiring from the engine ECM to the main controller. On used excavators, pay particular attention to harness routing near the turbo assembly and hydraulic pump drive area where heat and vibration cause insulation breakdown. Look for abraded wires, exposed copper, or oil-soaked connectors.

Step 2: Check Connector Integrity Disconnect and inspect the main ECM connector and KOMTRAX module connectors. Clean pins with electrical contact cleaner and check for bent pins, corrosion, or moisture intrusion. Use a digital multimeter to verify continuity between corresponding pins at each end of suspect harness sections (should read less than 5 ohms resistance).

Step 3: Test CAN Bus Communication Using Komatsu diagnostic software (KTCS or compatible tool), connect to the machine's diagnostic port and monitor real-time CAN bus traffic. Verify that data packets are transmitting between modules. Check for voltage levels on CAN High and CAN Low wires—should read approximately 2.5V at rest, with differential signaling between 1.5-3.5V during communication.

Step 4: Verify Termination Resistors Measure termination resistance across CAN High and CAN Low terminals with all modules connected—should read approximately 60 ohms (two 120-ohm resistors in parallel). Incorrect resistance indicates a failed termination resistor or open circuit.

Step 5: Update Software and Reset If wiring checks pass, connect to the machine using authorized Komatsu diagnostic equipment and verify that ECM firmware and KOMTRAX software are current. Perform a system reset and clear fault codes after addressing any physical issues found during inspection.

For used excavators, always replace suspect harness sections rather than attempting field repairs, as temporary fixes often fail under operational vibration and temperature cycling. Check service bulletins for this model year, as Komatsu may have issued updates addressing communication issues.

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Disclaimer: This guide provides general troubleshooting information for diagnostic purposes. Always consult the official Komatsu service manual for your specific machine serial number and consider engaging a certified Komatsu technician for complex electrical diagnostics, especially on machines still under warranty or service agreements.