What is Komatsu PC200-10 Fault Code DW91KA?

Fault Code DW91KA indicates a communication error or data inconsistency between the Engine Control Module (ECM) and the Hydraulic Control Unit (HCU) on the Komatsu PC200-10 excavator. This diagnostic trouble code specifically points to a malfunction in the CAN bus network that allows these critical control systems to exchange operational data.

The PC200-10 relies on seamless communication between the ECM and HCU to optimize fuel injection timing, hydraulic pump output, and engine load management. When code DW91KA appears, the machine's intelligent Machine Control system cannot properly coordinate engine power delivery with hydraulic demand. This is particularly critical on the PC200-10 because its KOMTRAX Plus system depends on this data link for monitoring performance, fuel efficiency, and emission controls. In used excavators, this communication fault often stems from degraded wiring harnesses or corrosion in connector pins—common issues after 5,000+ operating hours.

Common Symptoms

• Amber warning light illuminated on the monitor panel with reduced engine power output (derate mode)
• Sluggish hydraulic response during combined operations (swing and boom movement simultaneously)
• Intermittent engine surging or irregular idle, especially when hydraulic functions are engaged
• Error messages on the LCD display indicating "Controller Communication Error" or similar warnings
• Reduced fuel efficiency and black smoke during acceleration due to improper fuel-air mixture coordination

Potential Causes

The most frequent causes of DW91KA in used PC200-10 excavators include:

• Corroded or loose connectors at the ECM (located under the operator's cab) or HCU (mounted near the hydraulic pump)
• Damaged CAN bus wiring harness where it passes through the boom pivot point or along the chassis frame rails—a known rub point on this model
• Faulty termination resistors within the CAN network (120-ohm resistors should be present at network endpoints)
• ECM or HCU internal failure, though this is less common than harness issues in machines with 8,000+ hours
• Voltage irregularities from a weak alternator or poor battery connections affecting controller power supply
• Aftermarket component interference if non-OEM sensors or controllers were installed during previous repairs

How to Troubleshoot and Fix Code DW91KA

Step 1: Visual Inspection of Harness and Connectors Begin by inspecting the CAN bus wiring harness from the ECM to the HCU. On used PC200-10s, check specifically where the harness routes near the engine mounting brackets and hydraulic tank—these are high-friction areas. Look for abraded insulation, pinched wires, or evidence of rodent damage. Disconnect the multi-pin connectors at both the ECM (typically a 32-pin connector) and HCU (24-pin connector). Examine pins for green corrosion, bent contacts, or moisture intrusion. Clean connections with electrical contact cleaner and apply dielectric grease before reassembly.

Step 2: Test CAN Bus Integrity Using a digital multimeter, measure resistance between the CAN-High and CAN-Low terminals at the ECM connector (refer to the Komatsu service manual for exact pin locations—typically pins 23 and 24). You should read approximately 60 ohms with the system powered off, indicating proper termination resistors are in place. If you read infinite resistance, a termination resistor has failed or there's an open circuit in the network. If resistance is below 40 ohms, check for shorted wires.

Step 3: Voltage Supply Verification With the key in the "ON" position (engine off), verify that both the ECM and HCU are receiving proper supply voltage. Check for 24V DC at the power supply pins (consult wiring diagrams). Low voltage (below 22V) indicates charging system problems or excessive voltage drop through corroded main power cables—common in used machines with original batteries and cables.

Step 4: Advanced Diagnostics with Komatsu Software Connect Komatsu Diagnostic Explorer (KDPF) or equivalent dealer-level software to the diagnostic port under the cab. Monitor live data streams during code activation. Check the communication status between controllers—the software will show "No Communication" or "Intermittent" if the network is unstable. Perform a CAN bus oscilloscope test if available, looking for proper signal voltage (2.5V nominal with 1V differential between High and Low lines).

Step 5: Component Replacement Protocol For used excavators, never replace controllers first—95% of DW91KA codes are harness-related. If all wiring tests pass, replace termination resistors (inexpensive components, approximately $15 each). Only after confirming harness integrity and proper terminations should you consider ECM or HCU replacement. When installing new harnesses, secure them away from heat sources and moving components using proper cable ties and protective loom.

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Disclaimer: This guide provides general diagnostic information for experienced technicians. Always consult the official Komatsu PC200-10 service manual for model-specific procedures, torque specifications, and safety precautions. If you're unfamiliar with CAN bus diagnostics or high-voltage electrical systems, seek assistance from a certified Komatsu technician to avoid equipment damage or personal injury.