Komatsu PC160LC-7 Fault Code DW43KA: Complete Diagnostic Guide

What is Komatsu PC160LC-7 Fault Code DW43KA?

Fault Code DW43KA indicates a malfunction in the engine speed sensor circuit or an abnormal signal being received by the Engine Control Module (ECM). This code specifically relates to the engine's crankshaft position sensor system, which is critical for proper fuel injection timing and engine control.

The engine speed sensor on the PC160LC-7's SAA4D102E-2 engine provides real-time crankshaft position data to the ECM. When this signal is lost, intermittent, or falls outside acceptable parameters, the ECM triggers DW43KA and stores it in diagnostic memory. This fault is critical because the ECM relies on precise engine speed data to control fuel delivery, throttle response, and monitor overall engine performance. Without accurate speed sensing, the machine may experience severe performance degradation or fail to start entirely.

Common Symptoms

When DW43KA is active on your Komatsu PC160LC-7, you may experience:

• Engine cranks but fails to start or starts then immediately stalls
• Check engine warning light illuminated on the monitor panel
• Erratic engine RPM fluctuations during operation or at idle
• Loss of engine power or sudden derating to protect the engine
• Difficulty maintaining consistent hydraulic performance due to unstable engine speed

Potential Causes

The following issues commonly trigger DW43KA on used PC160LC-7 excavators:

• Faulty or worn engine speed sensor – common failure point on machines with 5,000+ operating hours
• Damaged sensor wiring harness – particularly where the harness runs near the engine block (known rub point on this model)
• Corroded or loose electrical connectors at the sensor or ECM terminals
• Damaged sensor reluctor ring on the crankshaft (less common but possible after major engine work)
• ECM internal faults – rare but can occur in high-hour machines or after electrical surges
• Poor ground connections affecting the sensor circuit integrity

How to Troubleshoot and Fix Code DW43KA

Step 1: Visual Inspection Begin by locating the engine speed sensor on the flywheel housing (driver's side of the engine). Inspect the wiring harness from the sensor to the ECM for visible damage, chafing, or breaks. On used excavators, check specifically where the harness contacts the engine block or frame rails—these are common wear points.

Step 2: Connector and Resistance Testing Disconnect the sensor connector and inspect for corrosion, moisture, or bent pins. Using a digital multimeter, measure the sensor's resistance across its terminals (typically 190-250 ohms for this model). Compare readings against Komatsu specifications in the service manual.

Step 3: Signal Voltage Check With the sensor reconnected, use a multimeter or oscilloscope to measure AC voltage while cranking the engine. You should see a fluctuating AC signal (typically 0.5-5V AC). No signal indicates a failed sensor or broken circuit.

Step 4: Air Gap Verification Check the air gap between the sensor tip and reluctor ring using a feeler gauge (specification: 0.5-1.5mm). Improper gap can cause weak or intermittent signals, especially in used machines where mounting brackets may have loosened.

Step 5: ECM and Ground Testing If the sensor tests good, verify continuity through the entire harness to the ECM. Test the ground circuit for resistance (should be less than 1 ohm). For used excavators with electrical history, check ECM pin connections for corrosion or backout.

Step 6: Component Replacement Replace the engine speed sensor if testing confirms failure. Use genuine Komatsu parts (Part #7861-93-1650 or equivalent) to ensure proper performance. Clear codes using Komatsu diagnostic software (KOMTRAX) and perform a test run.

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Disclaimer: This guide provides general diagnostic information for Komatsu PC160LC-7 excavators. Always consult the official Komatsu service manual and consider professional diagnosis for complex electrical issues. Working on heavy equipment electrical systems requires proper training and safety precautions.