What is Doosan Excavator Fault Code E002791-03?

Doosan fault code E002791-03 indicates a high voltage condition detected on the Engine Coolant Temperature (ECT) sensor circuit, signaling that the signal voltage has exceeded the acceptable upper threshold as defined by the Engine Control Module (ECM).

This code is part of Doosan's SAE J1939-based diagnostic framework, where the "-03" suffix specifically identifies a voltage above normal condition. The ECT sensor provides critical real-time data to the ECM for fuel injection timing, cooling fan control, and engine protection strategies. When this signal is compromised, the engine cannot accurately regulate thermal management — making this fault a priority concern.

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Common Symptoms

When E002791-03 is active on a Doosan excavator, operators typically experience:

• Illuminated warning lamp or fault indicator on the instrument cluster
• Engine derate mode activating, reducing power output to protect the drivetrain
• Inaccurate or pegged coolant temperature gauge readings (often stuck high or at maximum)
• Cooling fan running continuously at full speed as a failsafe response
• Potential automatic engine shutdown if the ECM interprets the signal as a true overheat condition

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Potential Causes

The following are the most likely root causes, especially relevant on used or high-hour machines:

• Open circuit in the ECT sensor signal wire — breaks the reference voltage loop, sending a false high-voltage signal
• Corroded or contaminated sensor connector — common on older Doosan DX and DL series machines exposed to mud and moisture
• Failed ECT sensor — internal resistance failure causing signal to rail high
• Chafed or damaged wiring harness — particularly near the engine block where heat and vibration cause insulation wear
• ECM power or ground fault — rare but possible on machines with prior electrical repairs

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How to Troubleshoot and Fix Code E002791-03

Step 1 — Retrieve and Document the Code Connect Doosan Diagnostic Software (DIAG-II or DoosanDMS) to the machine's diagnostic port. Confirm E002791-03 is active or stored, and check freeze frame data for operating conditions at fault activation.

Step 2 — Inspect the ECT Sensor and Connector Physically locate the ECT sensor on the engine block or coolant outlet. On used excavators, prioritize inspecting for connector corrosion, bent pins, moisture intrusion, and harness chafing before assuming sensor failure. Clean connectors with electrical contact cleaner.

Step 3 — Perform Voltage and Resistance Checks Using a digital multimeter, measure the sensor signal voltage at the connector with the key ON, engine OFF. A healthy ECT circuit typically reads 0.5V–4.5V. A reading near 5V or above confirms an open circuit or failed sensor. Measure sensor resistance across its terminals; compare against the manufacturer's temperature-resistance chart.

Step 4 — Repair or Replace Repair any damaged harness sections, replace corroded connectors, or install a new OEM-spec ECT sensor. Clear codes and perform a full operational test to confirm resolution.

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Disclaimer: This guide is intended for qualified heavy equipment mechanics and experienced operators. Always consult a certified Doosan technician or refer to the official Doosan service manual before performing repairs. Improper diagnosis or repair may void warranties or cause further machine damage.