What is Doosan Excavator Fault Code E000652-05?

Fault Code E000652-05 indicates a malfunction in the engine cooling system, specifically a "Coolant Temperature Sensor Circuit High Voltage" condition. This code triggers when the Engine Control Module (ECM) detects an abnormally high voltage signal from the coolant temperature sensor (CTS), typically exceeding 4.5-4.8 volts when normal operation should read between 0.5-4.5 volts depending on temperature.

In Doosan excavators, the coolant temperature sensor plays a critical role in engine management by monitoring coolant temperature and relaying data to the ECM. The ECM uses this information to adjust fuel injection timing, idle speed, and cooling fan operation. When this sensor circuit reads excessively high voltage—often indicating an open circuit or sensor failure—the ECM cannot properly manage engine temperature, potentially leading to overheating, poor fuel economy, and reduced engine protection.

Common Symptoms

When fault code E000652-05 is active, operators typically experience:

• Check Engine Light or warning lamp illuminated on the instrument cluster
• Engine running in derate mode or limp mode with reduced power output to prevent damage
• Cooling fan running continuously at maximum speed regardless of actual engine temperature
• Difficulty starting or rough idle, especially in cold conditions
• Inaccurate coolant temperature gauge readings (often showing maximum temperature immediately)

Potential Causes

The most common technical reasons for E000652-05 in used Doosan excavators include:

• Open circuit in the coolant temperature sensor wiring harness, often caused by wire breaks or connector damage
• Failed coolant temperature sensor with internal open circuit (common in machines with 5,000+ operating hours)
• Corroded or loose electrical connectors at the sensor or ECM, particularly on machines exposed to harsh environments
• Damaged sensor wiring due to rubbing against engine components, exhaust manifolds, or frame edges—a known issue near the thermostat housing area
• ECM internal fault (rare, but possible in older units with moisture intrusion)
• Improper repairs or aftermarket sensor installation with incorrect specifications

How to Troubleshoot and Fix Code E000652-05

Step 1: Visual Inspection Begin by locating the coolant temperature sensor (typically mounted on the thermostat housing or cylinder head). Inspect the sensor connector and wiring harness for obvious damage, corrosion, loose pins, or oil contamination. On used excavators, pay special attention to harness routing near hot engine surfaces where insulation may have melted or chafed through.

Step 2: Electrical Testing Disconnect the coolant temperature sensor connector. Using a digital multimeter, measure resistance across the sensor terminals. A functioning sensor should show resistance varying with temperature (approximately 2,000-3,000 ohms at 68°F/20°C). An open circuit (infinite resistance) confirms sensor failure. Also check for continuity in the wiring harness from sensor to ECM—any break indicates wiring repair is needed.

Step 3: Voltage Circuit Check With the ignition on and sensor disconnected, measure voltage at the harness connector. You should see approximately 5 volts reference voltage from the ECM. If voltage is absent, check for harness damage or ECM issues. If present, reconnect sensor and measure signal voltage—readings consistently above 4.5 volts confirm the high voltage condition.

Step 4: Repair or Replace Replace the coolant temperature sensor if testing confirms failure (common fix for used machines). If sensor tests good, repair damaged wiring, clean corroded connectors with electrical contact cleaner, and ensure proper harness routing away from heat sources. After repairs, clear the fault code using Doosan diagnostic software (DMS-5 or G-Scan) and verify coolant temperature readings match actual engine temperature during warm-up.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Doosan service manual for your specific model and consider professional diagnostic assistance for complex electrical issues or if you're unfamiliar with high-voltage systems.