What is Komatsu PC220-8 Fault Code DW91KB?

Fault Code DW91KB indicates a communication error between the machine's Engine Control Module (ECM) and the Hydraulic Pump Control System. This diagnostic trouble code specifically signals an interrupted or degraded data transmission on the CAN bus network that coordinates engine performance with hydraulic demand on the Komatsu PC220-8 excavator.

This code is critical because the PC220-8 relies on integrated communication between the SAA6D107E-1 engine controller and the hydraulic pump controller to optimize fuel efficiency and hydraulic power delivery. When this communication fails, the machine cannot properly match engine output to hydraulic load requirements, resulting in compromised performance and potential component protection modes.

Common Symptoms

• Reduced hydraulic power during combined operations (swing + boom movement simultaneously)
• Illuminated warning lamp on the monitor panel with corresponding error message
• Engine derating or automatic limitation to lower RPM ranges during high-demand tasks
• Erratic hydraulic response where attachment speed doesn't match joystick input consistently
• Intermittent loss of auto-idle or economy mode functionality

Potential Causes

The DW91KB code typically stems from issues common in used excavators with significant operating hours:

• CAN bus wiring harness damage at known rub points near the engine mounting brackets or along the right-side main frame rail
• Corroded or moisture-contaminated connectors at the ECM (located behind the cab) or hydraulic pump controller (mounted on pump housing)
• Failed terminating resistor on the CAN communication network
• ECM or pump controller internal failure due to voltage spikes or age-related component degradation
• Aftermarket electrical accessories improperly spliced into the machine's electrical system causing signal interference

How to Troubleshoot and Fix Code DW91KB

Step 1: Visual Harness Inspection Begin by inspecting the CAN bus harness running from the ECM to the hydraulic pump controller. On used PC220-8 models, check for harness wear where cables contact the engine block near the fuel filter assembly. Look for abraded insulation, pinched wires, or oil contamination on connectors.

Step 2: Connector and Pin Testing Disconnect both ECM and pump controller connectors. Use electrical contact cleaner to remove corrosion, and inspect pins for damage. With a digital multimeter, verify CAN-High and CAN-Low circuit continuity (typically 120-ohm resistance between terminals when network is powered down).

Step 3: Diagnostic Software Analysis Connect Komatsu KOMTRAX or compatible diagnostic software to read real-time communication data. Monitor CAN bus voltage levels (should fluctuate between 2.5-3.5V). If communication is absent, check the 120-ohm terminating resistors at network endpoints—failed resistors are common in machines over 8,000 hours.

Step 4: Component Replacement If wiring and connections test correctly, the issue likely resides in the pump controller module (more common) or ECM. On used excavators, always verify software versions match between controllers, as mismatched firmware can trigger communication faults.

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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 diagnostics for persistent issues.