What is Komatsu PC240LC-10 Fault Code DW91KB?

Fault Code DW91KB indicates a communication error or abnormal signal detected in the hydraulic system's pressure sensor circuit, specifically related to the pump control pressure monitoring system. This code is generated when the Engine Control Module (ECM) or Pump Control Unit detects an out-of-range voltage, intermittent signal, or complete loss of communication from the main hydraulic pump pressure sensor.

In the Komatsu PC240LC-10, this sensor is critical for monitoring system pressure to optimize fuel efficiency and hydraulic performance. When DW91KB triggers, the machine may enter a protective derate mode to prevent damage to hydraulic components, directly impacting productivity and operational costs on used equipment where sensor degradation is common.

Common Symptoms

• Dashboard warning light illuminated (typically amber hydraulic system indicator)
• Reduced hydraulic power or sluggish boom/arm/bucket response during operation
• Engine derate with RPM limited to approximately 1,500-1,800 range
• Intermittent code appearance that clears and returns, especially during cold starts
• Erratic pressure readings displayed on the monitor panel (if equipped with advanced display)

Potential Causes

The most common technical failures causing DW91KB on used PC240LC-10 excavators include:

• Pressure sensor failure due to internal diaphragm wear or contamination from hydraulic fluid breakdown
• Wiring harness damage at known rub points near the pump assembly where vibration causes insulation wear
• Corroded or loose connector pins at the sensor plug (C-314 connector), particularly on machines operating in wet or coastal environments
• ECM software glitches requiring calibration updates (known issue on 2014-2016 production models)
• Hydraulic fluid contamination causing sensor port blockage or membrane coating
• Voltage supply issues from the 5V reference circuit in the controller

How to Troubleshoot and Fix Code DW91KB

Step 1: Visual Inspection Begin by inspecting the pressure sensor located on the main hydraulic pump housing. Check the wiring harness for abrasion, particularly where it routes near the pump drive shaft. On used excavators, this is a critical wear point. Examine the connector (C-314) for corrosion, bent pins, or hydraulic oil contamination.

Step 2: Electrical Testing Using a digital multimeter, check the sensor's 5V reference voltage at the connector with the ignition on. Measure sensor output voltage (should range 0.5-4.5V depending on pressure). Check ground continuity and resistance (sensor resistance typically 200-500 ohms when disconnected). Use Komatsu KOMTRAX diagnostic software to monitor live sensor data.

Step 3: Component Replacement or Repair If voltage readings are correct but the code persists, replace the pressure sensor (Komatsu part #7861-93-1650). For harness damage common in used machines, repair wiring using heat-shrink connectors and reroute away from friction points. Clean corroded connectors with electrical contact cleaner before reassembly. After repairs, clear codes and perform a pressure calibration using diagnostic software.

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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 consider professional diagnostic services for complex electrical issues.