What is Doosan DX215-9C Fault Code E520710-12 (P108D)?

Fault Code E520710-12 (P108D) on the Doosan DX215-9C excavator indicates a malfunction in the Engine Coolant Temperature (ECT) sensor circuit, specifically detecting an intermittent or erratic voltage signal from the sensor to the Electronic Control Module (ECM). This code typically registers when the ECM detects irregular voltage patterns that fall outside the expected range during engine operation, but not consistently enough to trigger a complete circuit failure code.

This fault is critical for the DX215-9C because the ECT sensor provides essential data that the ECM uses to regulate fuel injection timing, engine protection systems, and cooling fan operation. When this sensor provides unreliable data, the engine may run inefficiently or activate protective derate modes to prevent overheating damage. For used excavators, this code often signals deteriorating electrical connections or sensor degradation from years of thermal cycling and vibration exposure.

Common Symptoms

• Intermittent check engine light or warning lamp that may illuminate and extinguish during operation
• Engine runs rough during cold starts but improves as it warms up, or vice versa
• Cooling fan operates erratically, running at high speed unnecessarily or not engaging when needed
• Reduced engine power or derate mode activation during heavy workloads as the ECM enters failsafe protection
• Inaccurate temperature gauge readings on the instrument cluster, showing fluctuating or frozen temperature displays

Potential Causes

• Corroded or loose connector pins at the ECT sensor harness connection—extremely common on used machines exposed to moisture and dirt
• Damaged wiring harness between the sensor and ECM, particularly at rub points near the engine block or frame rails where vibration causes insulation wear
• Failing ECT sensor with internal resistance breakdown due to thermal stress over thousands of operating hours
• Poor ground connection at the sensor mounting point or ECM ground strap, causing voltage instability
• ECM software glitch or moisture intrusion into the controller itself (less common but possible on older machines)

How to Troubleshoot and Fix Code E520710-12 (P108D)

Step 1: Visual Inspection Begin by locating the ECT sensor on the engine block (typically near the thermostat housing on DX215-9C models). Inspect the wiring harness and connector for obvious damage, corrosion, bent pins, or oil contamination. On used excavators, check for harness chafing against the engine or frame—this is a frequent failure point. Clean all connector contacts with electrical contact cleaner and apply dielectric grease.

Step 2: Test Sensor Resistance Disconnect the ECT sensor connector and use a digital multimeter to measure resistance across the sensor terminals. Compare readings against Doosan specifications (typically 2,000-3,000 ohms at room temperature, decreasing as temperature rises). If readings are erratic or out of range, replace the sensor. For used machines, even marginal readings suggest replacement is prudent.

Step 3: Check Circuit Voltage and Continuity With the sensor disconnected and ignition on (engine off), measure reference voltage at the harness connector—should read approximately 5 volts. Test continuity from the sensor connector back to the ECM pins using wiring diagrams. Repair any open circuits or shorts to ground. Pay special attention to ground integrity at both the sensor mounting point and ECM chassis ground.

Step 4: Monitor with Diagnostic Software Connect Doosan DMS (Diagnostic Master Software) or compatible diagnostic tool to monitor live ECT sensor data. Observe voltage fluctuations while gently wiggling the harness—sudden changes confirm intermittent connection issues. Clear codes after repairs and perform a full operational test under load.

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Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Doosan service manual for your specific machine serial number and safety procedures. If uncertain, contact a certified Doosan technician to avoid misdiagnosis or equipment damage.