What is Sany Excavator Fault Code P444?

Fault Code P444 indicates a malfunction in the engine coolant temperature sensor circuit, specifically detecting an intermittent or erratic signal from the coolant temperature sensor to the Engine Control Module (ECM). This code triggers when the ECM receives inconsistent voltage readings that fall outside the normal operating range or fluctuate unexpectedly during engine operation.

The coolant temperature sensor is critical for Sany excavators because it directly influences fuel injection timing, idle speed control, and engine protection protocols. When this sensor provides unreliable data, the ECM cannot accurately manage engine performance, potentially leading to fuel inefficiency, hard starting conditions, or activation of engine protection modes that limit machine productivity.

Common Symptoms

Operators may experience the following issues when Code P444 is active:

• Check Engine Light illuminated on the instrument panel, sometimes intermittently flickering
• Rough idling or inconsistent engine RPM, particularly during cold starts or warm-up periods
• Reduced engine power or derate mode activation as the ECM enters fail-safe operation
• Erratic temperature gauge readings that don't correspond to actual engine operating conditions
• Difficulty starting when the engine is cold, or extended cranking times

Potential Causes

Several factors commonly trigger P444 in used Sany excavators:

• Corroded or loose electrical connections at the coolant temperature sensor connector, especially common in machines with high operating hours
• Damaged wiring harness near the sensor location where cables may rub against engine components or frame edges
• Failing coolant temperature sensor due to internal resistance degradation or contamination from coolant leaks
• ECM grounding issues causing voltage fluctuations across multiple sensor circuits
• Coolant contamination affecting sensor accuracy, particularly in machines with deferred maintenance histories

How to Troubleshoot and Fix Code P444

Step 1: Visual Inspection Inspect the coolant temperature sensor and its wiring harness for obvious damage, corrosion, or coolant leaks. On used excavators, pay special attention to connector pins for green corrosion and harness routing where vibration may have caused wire chafing.

Step 2: Electrical Testing Using a digital multimeter, check the sensor's resistance at various temperatures. A functioning sensor typically shows approximately 2,500 ohms at 20°C (68°F). Verify supply voltage (typically 5V reference) and ground continuity at the sensor connector with the harness disconnected.

Step 3: Signal Monitoring Connect Sany diagnostic software or a compatible scan tool to monitor live coolant temperature data. Observe for erratic voltage spikes or dropouts while gently wiggling the harness—this reveals intermittent connection problems common in older machines.

Step 4: Component Replacement If testing confirms sensor failure, replace with an OEM or quality aftermarket sensor. Clean connector terminals with electrical contact cleaner and apply dielectric grease to prevent future corrosion. Clear codes and perform a test cycle.

Disclaimer: This guide provides general troubleshooting information. Always consult your Sany service manual and consider professional diagnostic assistance for complex electrical issues or if you're unfamiliar with excavator electrical systems.