What is Sany Excavator Fault Code P354?

Fault Code P354 indicates a malfunction in the Engine Coolant Temperature (ECT) Sensor Circuit, specifically detecting an intermittent or erratic signal from the sensor to the Engine Control Module (ECM). This diagnostic trouble code is triggered when the ECM receives inconsistent voltage readings that fall outside the expected parameters for normal engine operating temperatures, typically fluctuating beyond acceptable thresholds within a short timeframe.

The ECT sensor plays a critical role in Sany excavators by monitoring engine coolant temperature and transmitting this data to the ECM. This information directly influences fuel injection timing, idle speed control, and emission system operation. In used excavators, this code is particularly problematic because it can cause the ECM to operate in default mode, using substitute values that compromise fuel efficiency and engine protection systems. Ignoring P354 can lead to improper engine warm-up cycles, increased fuel consumption, and potential overheating damage on older machines with already-stressed cooling systems.

Common Symptoms

• Check Engine Light or warning lamp illuminated on the instrument cluster, sometimes accompanied by coolant temperature gauge erratic behavior
• Hard starting or extended cranking time, especially during cold starts when the ECM cannot determine proper fuel enrichment
• Rough idle or engine surging at low RPM as the ECM struggles to compensate for unreliable temperature data
• Reduced engine performance or unexpected power derate mode activation during operation
• Increased black smoke from exhaust due to improper fuel-to-air mixture calculations based on faulty temperature readings

Potential Causes

• Corroded or loose connector terminals at the ECT sensor—extremely common in used excavators exposed to moisture, dirt, and vibration over years of operation
• Damaged wiring harness between the sensor and ECM, particularly at known rub points near the engine block or frame rails where insulation wears through
• Failed ECT sensor with internal resistance degradation causing intermittent signal dropout
• Poor ground connection at the sensor mounting point due to rust, gasket deterioration, or thread corrosion
• ECM software glitches or internal ECM circuit board issues (less common but possible in high-hour machines)
• Coolant contamination causing sensor element fouling or mineral deposit buildup on the sensor tip

How to Troubleshoot and Fix Code P354

Step 1: Visual Inspection and Connector Check Begin by locating the ECT sensor (typically threaded into the engine block or thermostat housing). Disconnect the sensor connector and carefully inspect both the sensor pins and harness terminals for corrosion, bent pins, or moisture intrusion. On used excavators, clean terminals with electrical contact cleaner and apply dielectric grease. Check the sensor mounting threads for coolant leaks that could indicate gasket failure.

Step 2: Electrical Testing with Multimeter Using a digital multimeter, measure the resistance across the ECT sensor terminals with the sensor removed from the engine. Compare readings at different temperatures against Sany's specification chart (typically 2,000-3,000 ohms at 68°F/20°C). Test the wiring harness continuity from the sensor connector back to the ECM—resistance should be less than 5 ohms. Check for voltage supply from the ECM (usually 5V reference voltage) with the key on and engine off.

Step 3: Harness Inspection for Wear Points Trace the entire sensor harness route, paying special attention to areas where the wiring passes near hot engine components, sharp metal edges, or moving parts. In used machines, insulation breakdown at these friction points creates intermittent shorts to ground. Repair any damaged sections with heat-shrink tubing and secure with proper standoffs to prevent future chafing.

Step 4: Component Replacement and Verification If testing reveals sensor failure, replace the ECT sensor with an OEM or quality aftermarket part, ensuring proper torque specifications (typically 8-12 ft-lbs) and using new sealing washers. After replacement, clear the fault code using Sany diagnostic software or a compatible scan tool, then perform a cold-start test cycle to verify the code does not return. Monitor live data to confirm smooth temperature signal transitions during warm-up.

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Disclaimer: This guide provides general troubleshooting information for Sany excavator fault code P354. Always consult the manufacturer's service manual for your specific model and serial number. If you lack proper diagnostic tools or experience with electrical systems, seek assistance from a certified heavy equipment technician to avoid misdiagnosis or further damage to used machinery components.