What is Komatsu PC200-8E0 Fault Code DXE6KA?

Fault Code DXE6KA on the Komatsu PC200-8E0 excavator indicates an Engine Coolant Temperature (ECT) Sensor Circuit High Voltage condition detected by the Engine Control Module (ECM). This diagnostic trouble code means the ECM is receiving an abnormally high voltage signal from the coolant temperature sensor circuit, typically above 4.8 volts, when normal operating range should be between 0.5-4.5 volts depending on temperature.

This code is critical for the PC200-8E0's SAA6D107E-1 engine because the ECM relies on accurate coolant temperature data to optimize fuel injection timing, regulate engine speed, and prevent overheating damage. When the ECM cannot trust temperature readings, it may trigger derate modes that limit engine power to protect internal components.

Common Symptoms

• Engine warning lamp illuminated on the monitor panel (amber or red depending on severity)
• Engine derate or power reduction mode activated, limiting machine performance to 70-80% of normal output
• Difficult cold starts or rough idle conditions as the ECM defaults to cold-start fuel maps
• Higher than normal exhaust smoke during operation due to improper fuel compensation
• Cooling fan running continuously at high speed regardless of actual engine temperature

Potential Causes

The most common causes of DXE6KA on used PC200-8E0 excavators include:

• Open circuit in the ECT sensor wiring harness, often caused by wire chafing near the engine block mounting brackets (known wear point on this model)
• Failed ECT sensor with internal resistance breakdown, especially on machines with 6,000+ operating hours
• Corroded or loose connector terminals at the sensor plug due to coolant weepage or environmental moisture ingress
• Damaged ECM ground circuit affecting sensor reference voltage (less common but occurs on poorly maintained used units)
• Previous repair attempts using incorrect aftermarket sensors with improper resistance curves

How to Troubleshoot and Fix Code DXE6KA

Step 1: Visual Inspection Locate the ECT sensor on the thermostat housing (driver's side of engine). Inspect the two-wire connector for corrosion, bent pins, or coolant residue. Check the wiring harness from sensor to ECM for visible damage, particularly where it routes over the engine valve cover—a common rub point on used PC200-8E0 machines.

Step 2: Electrical Testing Using a digital multimeter, backprobe the sensor connector with the key ON, engine OFF. Measure voltage at the signal wire (typically green/white): you should see approximately 5 volts. If voltage reads near battery voltage (12V+), the signal wire is open. Next, measure sensor resistance with connector disconnected and engine cold: specification is 2.3-2.7 kΩ at 20°C (68°F). Values outside this range indicate sensor failure.

Step 3: Circuit Continuity Check Disconnect both the ECT sensor and the ECM connector X2 (located under the operator's cab floor). Test continuity between sensor harness pins and corresponding ECM terminals. Infinite resistance indicates an open wire requiring harness repair or replacement.

Step 4: Repair and Verification For used excavators, thoroughly clean all connector terminals with electrical contact cleaner before reassembly. Replace the sensor with a genuine Komatsu part (P/N 6261-81-7310) to ensure proper calibration. After repairs, clear codes using Komatsu diagnostic software (KTMS) or equivalent, and verify code does not return after 30 minutes of operation.

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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 or if you lack proper testing equipment.