What is Sany Excavator Fault Code P151?

Fault Code P151 on Sany excavators indicates a malfunction in the Engine Coolant Temperature (ECT) Sensor Circuit, specifically detecting a voltage signal that is higher than the normal operating range. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) receives an abnormally high voltage reading from the coolant temperature sensor, typically above 4.8-4.9 volts, suggesting an open circuit or sensor failure.

The ECT sensor plays a critical role in engine management by monitoring coolant temperature and sending real-time data to the ECM. This information directly affects fuel injection timing, idle speed control, and engine protection systems. When P151 activates, the ECM cannot accurately determine engine operating temperature, potentially causing the system to default to failsafe mode, which can significantly impact machine performance and fuel efficiency on used Sany excavators.

Common Symptoms

• Check Engine Light or malfunction indicator lamp illuminated on the instrument cluster
• Engine runs rough during cold starts or fails to reach optimal operating temperature
• Excessive fuel consumption due to ECM defaulting to cold-start enrichment mode
• Engine cooling fan running continuously at high speed regardless of actual temperature
• Reduced engine power or derate mode activation to prevent potential overheating damage

Potential Causes

The most common technical reasons for P151 on used Sany excavators include:

• ECT sensor internal failure or deterioration due to age and thermal cycling exposure
• Open circuit in the sensor wiring harness, often caused by wire chafing near the engine block or frame rails
• Corroded or loose electrical connectors at the sensor or ECM connection points
• Damaged sensor ground wire or poor ground connection to the engine block
• ECM internal fault (less common) affecting the sensor input circuit
• Previous repair attempts using incorrect sensor specifications or aftermarket components

How to Troubleshoot and Fix Code P151

Step 1: Visual Inspection Begin by locating the ECT sensor (typically installed in the engine coolant passage near the thermostat housing). Inspect the sensor connector for corrosion, moisture intrusion, or damaged pins. On used excavators, pay special attention to harness wear points where wires contact the engine or frame—this is a common failure point after years of vibration.

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 Sany service manual for exact specifications). Test the wiring harness for continuity between the sensor connector and ECM. Check for proper 5-volt reference voltage at the sensor connector with the key on, engine off.

Step 3: Component Replacement and Verification If the sensor tests out of specification or the harness shows open circuits, replace the faulty component with OEM or equivalent quality parts. Before installing a new sensor, clean the mounting threads and apply appropriate thread sealant. After repairs, clear the fault code using Sany diagnostic software or a compatible scan tool, then operate the machine through a complete warm-up cycle to verify the repair.

Disclaimer: This guide provides general troubleshooting information for educational purposes. Always consult your Sany service manual and consider professional diagnostic assistance for complex electrical issues, especially on used equipment with unknown maintenance history.