What is Sany Excavator Fault Code P154?

Fault Code P154 on Sany excavators indicates a malfunction in the Engine Coolant Temperature (ECT) Sensor Circuit, specifically detecting an abnormally high voltage signal or open circuit condition. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) receives a voltage reading from the ECT sensor that exceeds the normal operating range (typically above 4.5-4.8 volts), suggesting either a faulty sensor, damaged wiring, or poor electrical connections.

The ECT sensor plays a critical role in Sany excavator performance by monitoring engine temperature and providing data to the ECM for fuel injection timing, idle speed control, and cooling fan operation. When P154 is active, the ECM may default to a substitute temperature value, potentially causing inefficient combustion, increased emissions, and reduced engine protection against overheating—especially problematic in used machines with accumulated wear.

Common Symptoms

• Check Engine Light or Warning Lamp illuminated on the instrument cluster
• Hard starting, particularly in cold weather conditions, due to improper fuel enrichment
• Rough idle or irregular engine RPM fluctuations when the machine is at operating temperature
• Cooling fan running continuously at maximum speed, even when the engine is cold
• Reduced engine power or derate mode activation to protect against potential overheating damage

Potential Causes

The most common technical reasons for P154 in used Sany excavators include:

• Failed ECT sensor due to internal resistance breakdown or contamination from coolant degradation
• Open circuit in wiring harness—particularly at known rub points near the engine block or along the main harness routing behind the hydraulic pump
• Corroded or loose connector pins at the ECT sensor plug, common in machines exposed to harsh environments
• Damaged sensor ground circuit causing voltage reference problems
• ECM internal fault (rare, but possible in higher-hour used machines)
• Aftermarket coolant causing sensor element corrosion or coating buildup

How to Troubleshoot and Fix Code P154

Step 1: Visual Inspection Begin by locating the ECT sensor (typically mounted on the engine block or cylinder head). Inspect the electrical connector for corrosion, moisture intrusion, bent pins, or physical damage. On used excavators, check for harness chafing against engine components or frame rails—a common failure point.

Step 2: Electrical Testing Disconnect the ECT sensor connector. Using a digital multimeter, measure the resistance across the sensor terminals. A functional sensor typically reads 2,000-3,000 ohms at room temperature (refer to Sany specifications). If the reading shows infinite resistance (open circuit) or zero ohms (short circuit), replace the sensor.

Step 3: Wiring Harness Verification With the sensor disconnected, check continuity from the sensor connector back to the ECM pins using wiring diagrams. Verify the ground circuit has less than 1 ohm resistance. Inspect for voltage leakage by measuring voltage at the disconnected sensor harness—should read near 5 volts (reference voltage from ECM).

Step 4: Sensor Replacement and Verification Install a genuine or OEM-equivalent ECT sensor using proper torque specifications and apply dielectric grease to connector terminals. Clear the fault code using Sany diagnostic software or a compatible scan tool, then monitor for code recurrence during a complete heat cycle.

Disclaimer: This guide provides general troubleshooting information. Always consult Sany service manuals and qualified diesel technicians for machine-specific procedures, especially when working with used equipment that may have undocumented modifications or repairs.