What is Doosan Excavator Fault Code E001079-04?

Fault Code E001079-04 indicates a hydraulic oil temperature sensor circuit malfunction with a voltage signal that has remained low or out of range for an extended period. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects abnormal voltage readings from the hydraulic oil temperature sensor, typically below the manufacturer's specified threshold of approximately 0.5 volts for more than 4 seconds.

This fault is critical for Doosan excavators because the hydraulic system relies on accurate temperature monitoring to prevent overheating, maintain optimal viscosity, and protect expensive hydraulic components. When the ECM cannot accurately read hydraulic oil temperature, it may limit machine performance or activate protective derate modes to prevent catastrophic damage to pumps, motors, and cylinders.

Common Symptoms

• Hydraulic oil temperature warning light illuminated continuously on the instrument cluster
• Reduced hydraulic performance or slower cycle times as the ECM enters protective mode
• Fault code displayed on the monitor panel with possible audible alarm
• Intermittent loss of power during operation, especially under heavy loads
• ECM may default to a predetermined temperature value, potentially causing premature component wear

Potential Causes

The most common technical causes for E001079-04 in used Doosan excavators include:

• Failed hydraulic oil temperature sensor due to internal element degradation or moisture intrusion
• Damaged or corroded wiring harness between the sensor and ECM, particularly at connector pins
• Shorted sensor circuit to ground, often caused by harness chafing against frame members near the hydraulic tank
• Corroded connector terminals at the sensor plug or ECM interface due to water contamination
• Open circuit condition from broken wires inside the insulation jacket (common stress points near rotating platforms)
• ECM internal fault affecting the sensor input circuit (less common but possible in high-hour machines)

How to Troubleshoot and Fix Code E001079-04

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor (typically mounted on or near the hydraulic tank). Inspect the sensor connector and wiring harness for obvious damage, corrosion, oil contamination, or loose connections. On used excavators, pay special attention to harness routing where cables may rub against sharp edges or moving components.

Step 2: Electrical Testing Using a digital multimeter (DMM), disconnect the sensor and measure resistance across the sensor terminals. Compare readings against Doosan specifications (typically 200-300 ohms at 20°C, varying with temperature). Next, check for voltage supply at the harness connector with the ignition on—you should see approximately 5 volts reference voltage from the ECM.

Step 3: Circuit Continuity Check Test for continuity and shorts between the sensor wiring and ground. Inspect the entire harness path, especially through the swing joint area where wires experience repeated flexing. Check connector pin tension and clean all terminals with electrical contact cleaner.

Step 4: Component Replacement If the sensor tests faulty, replace it with a genuine Doosan hydraulic oil temperature sensor. If wiring is damaged, repair using proper gauge wire and weatherproof connectors, ensuring adequate strain relief. Clear codes using Doosan diagnostic software and perform a functional test monitoring live temperature data.

For used excavators, always verify that replacement sensors match OEM specifications, as aftermarket sensors may have different resistance curves causing false readings.

---

Disclaimer: This guide provides general troubleshooting information. Always consult the official Doosan service manual for your specific model and serial number. If you're uncomfortable performing electrical diagnostics, contact a certified Doosan technician to prevent further damage or safety hazards.