What is Komatsu PC110-8M0 Fault Code DW91KA?

Komatsu fault code DW91KA indicates a communication error between the engine ECM (Engine Control Module) and the machine's main controller or monitor panel. This fault occurs when the digital data link between these critical control systems fails or experiences signal degradation beyond acceptable parameters.

In the PC110-8M0 excavator, this code specifically points to a CAN bus communication failure affecting the machine's ability to properly coordinate engine performance with hydraulic system demands. This is critical because the ECM must continuously share data with the machine controller to optimize fuel delivery, power output, and operational efficiency. When this communication breaks down, the excavator cannot function at full capacity and may enter protective mode to prevent equipment damage.

Common Symptoms

• Amber or red warning lights illuminated on the instrument cluster, often accompanied by a communication error message on the monitor display
• Engine derate or power limitation, where the machine won't develop full horsepower even under load
• Intermittent loss of instrument panel readings, including RPM, coolant temperature, or fuel level gauges displaying erratic or frozen values
• Hydraulic system sluggishness due to inability of the ECM to communicate optimal engine load to match hydraulic demand
• Automatic shutdown or inability to start in severe cases where the controller cannot verify engine operating parameters

Potential Causes

The DW91KA code on used PC110-8M0 excavators typically stems from:

• Corroded or loose connector pins on the ECM harness or main controller wiring, especially common in machines with 3,000+ operating hours
• Damaged CAN bus wiring caused by harness chafing against the engine block or frame rails—a known wear point behind the fuel filter assembly on this model
• Failed terminating resistor in the CAN network, often located near the ECM mounting bracket
• ECM internal fault or corrupted software, particularly in machines that have experienced previous electrical issues or power surges
• Corroded ground connections at the battery tray or frame grounding points affecting signal integrity

How to Troubleshoot and Fix Code DW91KA

Step 1: Visual Inspection Begin by thoroughly inspecting all wiring harnesses between the ECM (located on the right side of the engine compartment) and the main controller. Look specifically for abraded insulation, corroded connectors, or moisture intrusion in connector boots. On used excavators, pay special attention to harness routing near the swing bearing where repetitive motion causes friction damage.

Step 2: Connector and Ground Verification Disconnect the 24-pin ECM connector and the main controller harness connector. Inspect pins for corrosion, bent contacts, or push-back. Use electrical contact cleaner and ensure pins seat fully when reconnected. Verify all chassis ground points show less than 0.5 ohms resistance to battery negative using a quality digital multimeter.

Step 3: CAN Bus Continuity Testing Using Komatsu diagnostic software (KOMTRAX Plus) or an aftermarket CANbus diagnostic tool, check for proper termination resistance. You should measure approximately 60 ohms between CAN-High and CAN-Low terminals with the system powered down. If resistance is infinite or near-zero, trace wiring for open circuits or shorts to ground.

Step 4: Signal Quality Assessment With the machine powered on (but not started), use the diagnostic software to monitor CAN bus voltage levels. CAN-High should read approximately 2.5-3.5V and CAN-Low around 1.5-2.5V during idle communication. Significant deviation indicates wiring resistance issues or a failing ECM.

Step 5: Component Replacement Strategy For used machines, prioritize replacing connectors and harness sections before condemning the ECM. Replace the CAN terminating resistor (approximately $15-30 part) if resistance values are incorrect. Only after confirming wiring integrity should you consider ECM replacement or reprogramming, which requires authorized Komatsu diagnostic equipment.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific serial number and consider professional diagnostic assistance for complex electrical issues. Improper electrical work can cause additional damage to sensitive electronic components.