What is Komatsu PC200-10 Fault Code DW91KB?

Fault Code DW91KB on the Komatsu PC200-10 excavator indicates a communication error or malfunction in the machine monitoring system's data network, specifically related to the Controller Area Network (CAN) bus communication between the engine control module (ECM) and the monitor panel. This code typically signals that the ECM is unable to properly transmit or receive operational data from one or more control units within the machine's integrated monitoring system.

This fault is critical because the PC200-10 relies on continuous CAN bus communication to coordinate engine performance, hydraulic functions, and operator alerts. When communication breaks down, the machine may enter derate mode or display inaccurate operational data, compromising both productivity and diagnostic capabilities. The Komatsu KOMTRAX system also depends on this network to transmit machine health data remotely.

Common Symptoms

When DW91KB is active on your PC200-10, operators typically experience:

• Monitor panel displays blank, frozen, or shows intermittent flickering of critical gauges (fuel level, coolant temperature, hydraulic oil temperature)
• Warning lights illuminate inconsistently or fail to activate when actual system faults exist
• Engine derate mode activation where power output is automatically reduced to protect the engine
• Loss of diagnostic capability through the monitor panel, preventing real-time troubleshooting
• KOMTRAX connectivity issues with incomplete or missing transmission data to remote monitoring platforms

Potential Causes

For used PC200-10 excavators, DW91KB typically stems from these technical issues:

• CAN bus wiring harness damage at known rub points near the engine bay bulkhead or along the right-hand side frame rail where harnesses contact structural components
• Corroded or moisture-contaminated connectors at the ECM (located under the operator cab) or monitor panel connections, especially in machines operating in wet or coastal environments
• Failed termination resistor on the CAN network (120-ohm resistors at network endpoints)
• ECM internal communication module failure due to voltage spikes or age-related component degradation
• Monitor panel circuit board failure, particularly in machines with 5,000+ operating hours where solder joints deteriorate

How to Troubleshoot and Fix Code DW91KB

Step 1: Visual Harness Inspection Begin with a thorough physical inspection of the CAN bus wiring harness from the ECM to the monitor panel. On used PC200-10s, check the harness routing behind the right-hand console and where it passes through the bulkhead. Look for abraded insulation, pinched wires, or signs of rodent damage. Inspect all connector pins for corrosion, bent terminals, or moisture infiltration.

Step 2: Electrical Continuity Testing Using a digital multimeter, disconnect battery power and measure resistance between CAN-High and CAN-Low terminals at both the ECM and monitor panel connectors. You should read approximately 60 ohms with the network intact (two 120-ohm terminating resistors in parallel). No continuity or infinite resistance indicates an open circuit in the harness. Check for shorts to ground on both CAN lines—resistance should exceed 10k ohms.

Step 3: Verify Termination Resistors Access the CAN bus termination points (typically at the ECM and the cab junction box). Disconnect one terminator and measure its resistance—it should read exactly 120 ohms. Failed resistors are common in used excavators subjected to electrical surges or improper jump-starting procedures.

Step 4: Diagnostic Software Analysis Connect Komatsu KDPF diagnostic software (Komatsu Diagnostic Program for Field) via the 9-pin diagnostic port beneath the monitor panel. Navigate to the network diagnostic screen to identify which specific control unit is dropping communication. The software will timestamp communication losses, helping identify intermittent connection issues that visual inspection might miss.

Step 5: ECM and Monitor Panel Testing If harness and resistors test properly, suspect the ECM communication module or monitor panel controller. For used excavators, swap the monitor panel with a known-good unit first (less expensive than ECM replacement). If the fault persists, the ECM's internal CAN transceiver may have failed. Before replacing the ECM (approximately $2,500-3,500 for genuine Komatsu units), verify supply voltage at the ECM—should be stable 24VDC with ignition on.

Critical Note for Used Equipment: Always clean and apply dielectric grease to all connectors during reassembly. Connector corrosion accounts for 60% of CAN communication faults in machines over 3 years old. Check for previous repair attempts that may have introduced wire splices or aftermarket connectors—these are common failure points.

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Disclaimer: This guide provides general troubleshooting information for the Komatsu PC200-10. Always consult the official Komatsu service manual for your machine's specific serial number range and software version. Complex electrical diagnostics should be performed by certified Komatsu technicians with proper diagnostic equipment. Improper repairs to the CAN network may cause additional control system damage.