What is Doosan Excavator Fault Code E000172-02?

Fault Code E000172-02 indicates a Circuit Voltage Below Normal condition in the Engine Coolant Temperature (ECT) Sensor circuit. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormally low voltage signal from the coolant temperature sensor, typically below 0.2-0.5 volts, which the system interprets as an open circuit or sensor malfunction.

The ECT sensor is critical for Doosan excavators because it directly influences fuel injection timing, engine warm-up protocols, and protective shutdown sequences. When this sensor circuit fails, the ECM cannot accurately monitor engine temperature, potentially leading to inefficient combustion, increased emissions, or inadequate engine protection during overheat conditions. For used excavators, this code often signals age-related deterioration in wiring harnesses or sensor degradation from years of thermal cycling.

Common Symptoms

• Check Engine Light or Engine Warning Lamp illuminated on the instrument cluster
• Engine may run in limp mode with reduced power output and RPM limitations
• Difficult cold starts or extended cranking time, especially in cooler weather
• Cooling fan may run continuously at high speed regardless of actual engine temperature
• Inaccurate temperature gauge readings, often showing extremely cold temperatures even when engine is warm

Potential Causes

The most common technical reasons for Code E000172-02 in used Doosan excavators include:

• Open circuit in the ECT sensor wiring harness due to wire breaks, particularly near flex points around the engine block
• Corroded or loose connector terminals at the ECT sensor plug—common in machines with high operating hours in wet or corrosive environments
• Failed coolant temperature sensor itself, often caused by internal element failure or coolant contamination
• Damaged sensor ground circuit or poor ground connection at the ECM
• Chafed wiring where harnesses contact engine components or frame rails (known issue on older Doosan models)
• ECM internal circuit failure (less common, but possible in high-hour machines)

How to Troubleshoot and Fix Code E000172-02

Step 1: Visual Inspection Begin with a thorough inspection of the ECT sensor and its wiring harness. The sensor is typically located on the engine block near the thermostat housing. Check for obvious damage, coolant leaks around the sensor, or corroded connector pins. On used excavators, pay special attention to harness routing where wires may have rubbed against hot or moving components over thousands of operating hours.

Step 2: Electrical Testing Disconnect the ECT sensor connector and use a digital multimeter to check sensor resistance. At room temperature (68°F/20°C), resistance should typically read 2,000-3,000 ohms (consult your specific Doosan service manual for exact specifications). Next, check for continuity between the sensor signal wire and the ECM connector—any infinite resistance indicates an open circuit requiring harness repair.

Step 3: Voltage and Ground Verification With the ignition on and sensor disconnected, measure reference voltage at the sensor connector from the ECM—should read approximately 5 volts. Check the ground circuit for less than 0.1 ohms resistance to chassis ground. If voltage or ground is absent, trace wiring back to the ECM for breaks or poor connections.

Step 4: Component Replacement and Verification If sensor and wiring test faulty, replace the ECT sensor using OEM or quality aftermarket parts. Before installation, apply dielectric grease to connector terminals to prevent future corrosion. Clear the fault code using Doosan diagnostic software (DX-DATA or equivalent scan tool) and perform a functional test by monitoring live coolant temperature data during engine warm-up.

Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Doosan service manual for your specific model. If you're uncertain about electrical diagnostics or repairs, seek assistance from a certified Doosan technician to avoid further damage to the machine's electrical system.