What is Doosan DX150LC-9C Fault Code E000736-05?

Fault Code E000736-05 indicates a malfunction in the engine coolant temperature sensor circuit, specifically detecting an abnormal voltage signal (typically out-of-range high) from the ECT (Engine Coolant Temperature) sensor to the ECM (Engine Control Module). This code is part of Doosan's standardized diagnostic system for their DL06 engine platform used in the DX150LC-9C 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 controls fuel injection timing, idle speed, and cooling fan operation. When the ECM detects voltage readings outside the expected range (usually 0.5-4.5V), it triggers E000736-05 to prevent engine damage from incorrect temperature assumptions. For used excavators, this code is particularly important as prolonged operation with faulty temperature readings can cause overheating, excessive fuel consumption, or premature engine wear.

Common Symptoms

• Check Engine light or malfunction warning lamp illuminated on the instrument cluster
• Engine running in cold start mode continuously, resulting in rough idle and black smoke from exhaust
• Cooling fan running constantly at maximum speed, even when engine is cold
• Difficulty starting in cold weather conditions or extended cranking time
• Noticeable increase in fuel consumption and reduced engine performance under load

Potential Causes

The most common technical causes for E000736-05 on used DX150LC-9C excavators include:

• Failed ECT sensor due to internal resistance breakdown (common after 5,000+ operating hours)
• Corroded or loose connector at the sensor harness connection point near the thermostat housing
• Damaged wiring harness between sensor and ECM, often caused by rubbing against engine block or heat shield deterioration
• Coolant contamination on sensor tip causing false readings (especially in machines with poor maintenance history)
• ECM internal circuit failure (rare, but possible in high-hour used machines)
• Improper sensor installation after previous repair, including overtightened threads or missing sealing washer

How to Troubleshoot and Fix Code E000736-05

Step 1: Visual Inspection Begin with the engine cool. Locate the ECT sensor on the engine block near the thermostat housing (driver's side). Inspect the two-pin connector for corrosion, moisture, or pushed-back pins. Check the wiring harness for visible damage, particularly where it passes near moving components or hot exhaust manifold. On used excavators, pay special attention to harness chafing points where zip ties may have deteriorated.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to measure resistance across the sensor terminals. At 20°C (68°F), resistance should read approximately 2,400-2,700 ohms. Compare readings to Doosan's temperature-resistance chart. Next, check harness continuity from the connector back to the ECM pins (typically E2-34 and E2-35). Resistance should be less than 5 ohms with no shorts to ground.

Step 3: Voltage Signal Verification With ignition ON (engine off), backprobe the sensor connector and measure voltage between signal wire and ground. You should see approximately 5V reference voltage from the ECM. If voltage is absent or incorrect, suspect ECM issues or harness damage. If voltage is correct but code persists, replace the ECT sensor using OEM or equivalent quality parts with proper thread sealant (not Teflon tape).

Step 4: Post-Repair Verification After repairs, clear codes using Doosan diagnostic software (EPOS, G-Scan) or compatible scan tool. Run the engine through a full heat cycle (cold start to operating temperature) and monitor live data. Verify coolant temperature readings match actual conditions and that cooling fan cycles properly.

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