Komatsu PC70-8 Fault Code DW43KA: Complete Diagnostic Guide

What is Komatsu PC70-8 Fault Code DW43KA?

Fault Code DW43KA indicates a communication error or abnormal signal between the engine controller (ECM) and the hydraulic system controller on the Komatsu PC70-8 excavator. This code specifically relates to the CAN bus communication network that allows the engine and hydraulic systems to coordinate operations efficiently.

This fault affects the integrated control system that manages engine output relative to hydraulic demand. The PC70-8 relies on continuous data exchange between controllers to optimize fuel efficiency and prevent overloading. When communication breaks down, the machine cannot properly regulate power distribution, potentially leading to reduced performance or protective shutdowns. For used excavators, this code often signals deteriorating electrical connections or controller aging that requires immediate attention to prevent costly downtime.

Common Symptoms

When DW43KA is active, operators typically experience:

• Warning light illumination on the instrument panel, often accompanied by a diagnostic trouble code display
• Reduced engine power or hydraulic response, as the system enters a protective derate mode
• Intermittent loss of auxiliary functions such as swing speed control or attachment hydraulics
• Erratic engine RPM behavior when operating under load, particularly during combined movements
• Complete machine shutdown in severe cases where communication is entirely lost

Potential Causes

The most common technical reasons for DW43KA on used PC70-8 excavators include:

• Corroded or loose CAN bus connectors at the ECM or hydraulic controller, especially in machines exposed to moisture
• Damaged wiring harness along known rub points near the engine mount or swing bearing area
• Failed termination resistors in the CAN network causing signal reflection and data corruption
• ECM or hydraulic controller internal failure, more common in high-hour machines (5,000+ hours)
• Voltage supply issues from aging batteries or failing alternators affecting controller stability
• Software version mismatches after component replacement without proper reprogramming

How to Troubleshoot and Fix Code DW43KA

Step 1: Visual Inspection Begin by thoroughly inspecting all wiring harnesses between the engine ECM (located near the battery box) and the hydraulic controller. Check for chafing, cuts, or corrosion at connector pins. On used excavators, pay special attention to harness routing near moving components where vibration causes wear.

Step 2: Electrical Testing Using a digital multimeter, verify CAN-High and CAN-Low voltage at both controllers. You should measure approximately 2.5V on each line with the key on, engine off. Check for 120-ohm resistance across CAN-High and CAN-Low terminals when measuring termination resistors. Voltage outside the 2.0-3.0V range indicates wiring faults or controller issues.

Step 3: Connector Service Disconnect and clean all CAN bus connectors with electrical contact cleaner. Inspect for bent pins or moisture intrusion. Apply dielectric grease to prevent future corrosion—critical for used machines operating in harsh environments.

Step 4: Diagnostic Software Analysis Connect Komatsu KOMTRAX or compatible diagnostic software to read live data streams. Monitor communication status between controllers during operation. Intermittent dropouts point to harness issues, while complete absence suggests controller failure.

Step 5: Component Replacement If testing confirms controller failure, replacement requires software configuration matching your machine's specifications. For used excavators, consider sourcing remanufactured controllers to reduce costs while ensuring proper programming.

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Disclaimer: This guide provides general diagnostic information. Complex electrical issues should be evaluated by certified Komatsu technicians with proper diagnostic equipment. Always consult your service manual and follow safety protocols when working on heavy equipment.