What is Doosan Excavator Fault Code E001079-02?

Fault Code E001079-02 indicates an Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage condition in Doosan excavators. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects an abnormally low voltage signal from the coolant temperature sensor circuit, typically below 0.2-0.5 volts depending on the specific engine model.

The ECT sensor plays a critical role in engine management by monitoring coolant temperature and sending real-time data to the ECM. This information directly affects fuel injection timing, idle speed control, and engine warm-up procedures. When the ECM receives a voltage signal outside the expected range, it registers this fault to prevent potential engine damage from operating with incorrect temperature data. For used excavators, this code is particularly important as it can indicate aging electrical components or corroded connections that compromise engine efficiency and longevity.

Common Symptoms

• Check Engine Light or Engine Warning Lamp illuminated on the instrument cluster
• Engine running rich with black smoke from the exhaust due to incorrect fuel mixture calculations
• Hard starting conditions, especially in cold weather, as the ECM cannot properly adjust for temperature
• Engine may run at higher than normal idle speed continuously, as the ECM defaults to cold-start parameters
• Potential engine derate mode or reduced power output on some Doosan models as a protective measure

Potential Causes

The most common technical causes for Code E001079-02 in used Doosan excavators include:

• Shorted ECT sensor or internal sensor failure causing resistance values outside specifications (typically 2,000-3,000 ohms at room temperature)
• Damaged wiring harness between the sensor and ECM, particularly at known rub points near the engine block or frame rails
• Corroded or loose connector pins at the sensor or ECM—extremely common in machines with high hours or exposure to moisture
• Broken or frayed ground wire in the sensor circuit, creating an incomplete electrical path
• Failed ECM (rare but possible in high-hour machines), unable to properly read sensor voltage
• Coolant contamination on sensor terminals causing electrical shorts in older equipment

How to Troubleshoot and Fix Code E001079-02

Step 1: Visual Inspection Begin with a thorough physical examination of the ECT sensor located on the engine block (typically near the thermostat housing). Check the electrical connector for corrosion, bent pins, moisture intrusion, or physical damage. On used excavators, pay special attention to the wiring harness routing—look for areas where insulation may have rubbed through against metal surfaces, a common issue after thousands of operating hours.

Step 2: Electrical Testing Using a digital multimeter, disconnect the ECT sensor connector and measure the sensor's resistance. At approximately 68°F (20°C), resistance should read between 2,000-3,000 ohms (consult your specific Doosan service manual for exact specifications). Next, check for continuity between the sensor terminals and ground—there should be no continuity, indicating no short to ground. Measure the supply voltage at the harness connector with the key on, engine off; you should see approximately 5 volts reference voltage from the ECM.

Step 3: Circuit and Harness Verification If the sensor tests within specifications, inspect the entire wiring harness from sensor to ECM. Check for voltage drops, using your multimeter to verify continuity through each wire. For used machines, remove protective loom covering and physically inspect for wire chafing, corrosion, or breaks. Test the ground circuit independently—poor grounds are extremely common in older equipment.

Step 4: Component Replacement and Verification If testing confirms sensor failure, replace the ECT sensor with a genuine Doosan or OEM-equivalent part. Clean the sensor mounting location and apply appropriate thread sealant. After replacement, clear the fault code using Doosan diagnostic software (DX or G1 series software) or a compatible J1939 diagnostic tool. Run the engine through a complete warm-up cycle and verify the code does not return.

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Disclaimer: This guide provides general diagnostic information for Code E001079-02. Always consult the official Doosan service manual for your specific excavator model and serial number. If you're uncomfortable performing electrical diagnostics, contact a certified Doosan technician or qualified heavy equipment mechanic to prevent further damage to electrical systems.