What is Komatsu PC110-8M0 Fault Code DW43KB?

Fault Code DW43KB on the Komatsu PC110-8M0 excavator indicates a communication error between the Engine Control Module (ECM) and the Monitor Control Module (MCM). This diagnostic trouble code (DTC) specifically points to an interruption or degradation in the CAN bus (Controller Area Network) data transmission between these two critical control units.

The PC110-8M0 relies on continuous digital communication between the ECM and MCM to coordinate engine performance, display operational data, and manage warning systems. When this communication link fails or experiences signal interference, the system defaults to storing code DW43KB. This is particularly critical because the MCM cannot accurately display engine parameters, fault warnings, or operational alerts without proper ECM communication, potentially masking other developing issues and compromising machine safety.

Common Symptoms

When DW43KB is active on your Komatsu PC110-8M0, operators typically experience:

• Monitor panel errors or blank displays – The LCD screen may show incorrect data, freeze, or fail to display engine parameters entirely
• Multiple simultaneous warning lights – The machine may illuminate several unrelated warning indicators due to communication failure
• Intermittent gauge readings – Fuel level, temperature, and pressure gauges may fluctuate erratically or read zero
• Engine derate mode – In some cases, the ECM may limit engine power as a protective measure when monitor communication is lost
• Stored multiple fault codes – Secondary codes may appear as modules fail to confirm proper system operation

Potential Causes

For used Komatsu PC110-8M0 excavators, DW43KB commonly stems from:

• CAN bus wiring harness damage – Particularly at the harness routing behind the operator's seat and along the right-side frame rail where vibration and rubbing are common
• Corroded or moisture-contaminated connectors – The 24-pin ECM connector and 16-pin MCM connector are vulnerable to moisture intrusion in older machines
• Damaged termination resistors – The CAN network requires proper 120-ohm termination resistors at each end; corrosion or physical damage causes signal reflection
• Failed ECM or MCM module – Less common, but internal circuit board failures occur in high-hour machines
• Aftermarket accessory interference – Improperly installed radio systems, GPS trackers, or auxiliary lighting can create electrical noise on the CAN bus

How to Troubleshoot and Fix Code DW43KB

Step 1: Visual Inspection of Harness and Connectors

Begin by inspecting the main wiring harness between the ECM (located under the right-side service panel) and the MCM (behind the monitor panel). Look specifically for harness wear points where cables contact the frame, evidence of previous repairs with electrical tape, or areas where rodents may have damaged insulation. On used excavators, check connector pins for green corrosion, bent terminals, or moisture inside connector boots.

Step 2: Measure CAN Bus Resistance

Using a quality digital multimeter, disconnect power and measure resistance across the CAN-High and CAN-Low terminals at the ECM connector. You should read approximately 60 ohms (two 120-ohm resistors in parallel). If you measure open circuit (infinite resistance), a termination resistor has failed or there's a break in the CAN wiring. If resistance is significantly lower, there may be a short circuit.

Step 3: Check for Voltage and Signal Integrity

With the key on and engine off, measure voltage between CAN-High and CAN-Low terminals—you should see approximately 2.5V DC. During cranking or operation, use a digital oscilloscope or Komatsu KOMTRAX diagnostic software to observe signal quality. Look for clean square waves with proper amplitude (typically 2-3V differential). Excessive noise, signal distortion, or voltage spikes indicate electrical interference or failing modules.

Step 4: Isolate and Test Individual Modules

If wiring checks pass, systematically disconnect non-essential CAN bus devices (auxiliary controllers, aftermarket accessories) to identify interference sources. For used machines with multiple previous owners, unauthorized electrical modifications are common culprits. Test the ECM and MCM independently using Komatsu diagnostic software to verify internal functionality before condemning either component.

Important for Used Equipment: Before replacing expensive modules, thoroughly clean all connector terminals with electrical contact cleaner, apply dielectric grease, and ensure proper harness routing with new zip ties and protective loom. Many DW43KB codes on older PC110-8M0 machines resolve with connector maintenance alone.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific machine serial number and seek assistance from certified Komatsu technicians for complex electrical diagnostics or ECM/MCM replacement procedures.