What is Komatsu PC210LC-10 Fault Code DW91KA?

Fault Code DW91KA indicates a communication error or abnormal signal from the hydraulic pump control system on the Komatsu PC210LC-10 excavator. Specifically, this code relates to a malfunction in the data transmission between the Engine Control Module (ECM) and the Pump Control Unit (PCU), which manages main hydraulic pump output and pressure regulation.

This code is critical for the PC210LC-10 because the hydraulic pump control directly affects excavator performance, cycle times, and fuel efficiency. When the ECM cannot properly communicate with the PCU, the machine may enter a derated mode to protect the hydraulic system from over-pressurization or erratic operation. In used excavators with higher operating hours, electrical connection degradation is a common trigger for this fault.

Common Symptoms

When fault code DW91KA is active on your Komatsu PC210LC-10, operators typically experience:

• Amber or red warning light illuminated on the monitor panel with code display
• Reduced hydraulic power or sluggish boom/arm/bucket movements
• Erratic engine RPM fluctuation during hydraulic operations
• Automatic power derate limiting engine output to protect the system
• Intermittent fault activation that clears and reappears, especially in cold weather or after machine warm-up

Potential Causes

The most common technical causes for DW91KA on used PC210LC-10 excavators include:

• Corroded or loose connector pins on the PCU harness (especially the 38-pin connector near the main pump)
• Damaged CAN bus wiring between the ECM and PCU, particularly where harnesses route over the turntable bearing
• Failed Pump Control Unit due to internal circuit board degradation or moisture intrusion
• ECM software version mismatch or corrupted calibration files after previous repairs
• Voltage supply issues to the PCU from damaged power supply wiring or weak alternator output
• Mechanical wear on the pump regulator causing feedback sensor signal drift

How to Troubleshoot and Fix Code DW91KA

Step 1: Visual Inspection of Harnesses and Connectors Begin by inspecting the pump control harness routing from the ECM (located behind the operator cab) to the PCU (mounted on the main hydraulic pumps). On used machines, check for harness chafing points where wires cross the swing bearing or contact metal edges. Disconnect and inspect the 38-pin PCU connector for corrosion, bent pins, or moisture. Clean connectors with electrical contact cleaner and apply dielectric grease.

Step 2: Test Communication Circuit Continuity Using a digital multimeter, check continuity on the CAN-H and CAN-L communication lines between ECM pins and PCU connector terminals (refer to Komatsu wiring diagram for your specific serial number). Resistance should measure 55-65 ohms between CAN-H and CAN-L with connectors disconnected. Check for shorts to ground on both lines—readings should show open circuit (OL).

Step 3: Verify Power Supply and Ground Circuits Measure battery voltage (12-14V) at the PCU power supply pin with ignition on. Check ground circuit resistance—should be less than 0.5 ohms to chassis ground. In used excavators, ground connection corrosion is extremely common and often overlooked.

Step 4: Diagnostic Software Analysis Connect Komatsu KOMTRAX Plus or compatible diagnostic software to the service port. Monitor live data from the PCU during operation to identify intermittent signal dropouts. Check for additional stored codes that may indicate ECM or sensor issues. Update ECM software to the latest version if outdated calibrations are detected.

Step 5: Component Replacement Verification If all circuits test normal but the fault persists, the PCU itself may have failed internally. Before replacing the $1,200-1,800 PCU, verify the main pump mechanical regulator operates smoothly without binding—mechanical issues can cause electrical faults to register. After any component replacement, perform a system calibration using diagnostic software and clear all fault codes.

---

Disclaimer: This guide provides general troubleshooting information for experienced diesel mechanics. Always consult the official Komatsu PC210LC-10 service manual for your machine's specific serial number range. If you're uncomfortable with electrical diagnostics or lack proper tools, contact a certified Komatsu technician to prevent costly misdiagnosis or equipment damage.