Komatsu PC750LC-7 Fault Code DW43KA: Complete Diagnostic Guide

What is Komatsu PC750LC-7 Fault Code DW43KA?

Fault Code DW43KA indicates a communication error or abnormal signal between the machine's Engine Control Module (ECM) and the Hydraulic Control System, specifically related to the pump control circuit or pressure sensor feedback loop. This code is part of Komatsu's proprietary diagnostic system used in the Dash-7 series excavators.

The PC750LC-7 relies on precise coordination between engine output and hydraulic demand through continuous CAN bus communication. When the ECM cannot properly receive or interpret signals from the hydraulic pressure sensors or pump control solenoids, it triggers DW43KA to prevent potential system damage. This is critical because improper pump control can lead to overheating, reduced digging force, or catastrophic hydraulic failure in this 165,000-pound machine.

Common Symptoms

When DW43KA is active, operators typically experience:

• Reduced hydraulic response or sluggish boom/arm movements, particularly under load
• Engine derate mode where RPM is limited to protect the drivetrain
• Warning lamp illumination on the monitor panel with accompanying fault code display
• Intermittent loss of auxiliary hydraulic functions (breaker circuits, thumb controls)
• Unusual engine hunting or RPM fluctuation during hydraulic operations

Potential Causes

The most common technical causes for DW43KA in used PC750LC-7 excavators include:

• Corroded or damaged wiring harness connections between the ECM and main hydraulic pump (known wear point near the swing bearing)
• Failed hydraulic pressure sensor (typically the main pump pressure transducer)
• Faulty pump control solenoid valve with internal coil degradation
• CAN bus communication failure due to damaged shielding or poor ground connections
• ECM software corruption or outdated firmware version
• Contaminated hydraulic oil affecting sensor accuracy and solenoid operation

How to Troubleshoot and Fix Code DW43KA

Step 1: Initial Inspection Connect Komatsu KOMTRAX or compatible diagnostic software to read live data parameters. Check hydraulic pressure sensor readings at idle and under load. Physically inspect the main wiring harness routing from the ECM (located behind the operator cab) to the hydraulic pump area for chafing, oil contamination, or connector corrosion—a common issue in used machines with 8,000+ hours.

Step 2: Electrical Testing Using a digital multimeter, test the hydraulic pressure sensor output (typically 0.5-4.5V range). Check pump control solenoid resistance (should be 10-15 ohms). Verify CAN bus voltage at the ECM connector (2.5V nominal on both CAN-H and CAN-L lines). For used excavators, pay special attention to ground integrity—clean and retorque all chassis ground points.

Step 3: Component Replacement If sensors test out of specification, replace the main pump pressure transducer first (Komatsu part 7861-93-1650). If electrical values are correct but the code persists, the pump control solenoid valve may require replacement. Before installing new parts on used equipment, thoroughly clean all connector pins with electrical contact cleaner and apply dielectric grease.

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.