What is Doosan DX215-9C Fault Code E001207-01 (P0668)?

Fault Code E001207-01 (P0668) indicates an Engine Coolant Temperature (ECT) sensor circuit malfunction or an abnormal voltage signal being sent to the Engine Control Module (ECM). This diagnostic trouble code specifically relates to the primary coolant temperature sensor's electrical circuit, which monitors engine operating temperature and communicates critical thermal data to the machine's electronic control system.

In the Doosan DX215-9C excavator, this code directly affects the ECM's ability to properly manage fuel injection timing, idle speed control, and engine protection protocols. The coolant temperature sensor plays a vital role in cold-start enrichment, optimal combustion efficiency, and preventing engine overheating damage. When this circuit fails, the ECM operates in a default "limp mode" using predetermined temperature values, which significantly reduces machine performance and fuel efficiency.

Common Symptoms

When Code E001207-01 is active on your DX215-9C, operators typically experience:

• Check Engine Light illuminated on the instrument cluster with reduced engine power
• Difficulty starting the engine when cold, or excessive cranking time
• Engine running rough at idle or stalling during warm-up phase
• Cooling fan running continuously at high speed regardless of actual engine temperature
• Abnormal fuel consumption and black smoke from exhaust during operation

Potential Causes

The most common technical reasons for this fault code on used Doosan excavators include:

• ECT sensor internal resistance failure due to age and thermal cycling (extremely common after 5,000+ hours)
• Corroded or damaged connector pins at the sensor harness connection point
• Chafed or broken wiring in the engine harness, particularly where it routes near the exhaust manifold or engine block
• ECM internal circuit board damage from moisture intrusion or voltage spikes
• Faulty ground connection between the sensor circuit and chassis ground
• Contaminated coolant causing sensor element degradation or coating buildup

How to Troubleshoot and Fix Code E001207-01 (P0668)

Step 1: Visual Inspection Begin by inspecting the ECT sensor located on the engine block near the thermostat housing. Check the connector for corrosion, bent pins, or coolant contamination. On used excavators, this connector frequently suffers from environmental exposure and vibration damage. Clean connections with electrical contact cleaner and inspect for proper seal integrity.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. At 68°F (20°C), resistance should read approximately 2,000-3,000 ohms (consult your service manual for exact specifications). Next, check the harness side for continuity to the ECM and verify proper ground circuit resistance (should be less than 5 ohms).

Step 3: Voltage Signal Check With the sensor connected and ignition on (engine off), backprobe the signal wire at the connector. You should read approximately 4.5-5.0 volts (reference voltage from ECM). If voltage is absent or incorrect, trace the wiring for damage or test ECM output capability using Doosan diagnostic software.

Step 4: Component Replacement If sensor resistance is out of specification or harness damage is found, replace the faulty component. For used machines, always replace the connector pigtail simultaneously to prevent recurring issues from corroded terminals. After replacement, clear codes using Doosan DoosanCONNECT diagnostic software and verify proper operation through a complete heat cycle.

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Disclaimer: This guide provides general diagnostic information. Always consult your Doosan service manual and consider professional assistance for complex electrical diagnostics, especially when dealing with ECM-related issues on used heavy equipment.