What is Sany Excavator Fault Code P944?

Fault Code P944 indicates a malfunction in the Engine Coolant Temperature (ECT) sensor circuit, specifically detecting an abnormal voltage signal or out-of-range reading that falls outside the Engine Control Module's (ECM) expected parameters. This diagnostic trouble code (DTC) is triggered when the ECM receives sensor data that suggests either an implausibly high or low temperature reading, often caused by electrical circuit issues rather than actual engine overheating.

For Sany excavators, the ECT sensor plays a critical role in fuel injection timing, engine protection protocols, and hydraulic system optimization. When this sensor circuit fails, the ECM cannot accurately monitor engine temperature, potentially leading to improper fuel delivery, reduced performance, and increased risk of engine damage. In used machinery, this code frequently appears due to age-related wiring degradation or connector corrosion rather than sensor failure itself.

Common Symptoms

• Check Engine Light or Engine Warning Lamp illuminated on the instrument cluster
• Engine running in limp mode or derate condition, limiting maximum RPM and hydraulic performance
• Difficulty starting in cold conditions or excessive white smoke during warm-up due to improper fuel enrichment
• Erratic temperature gauge readings that fluctuate abnormally or remain stuck at cold position
• Cooling fan running continuously at maximum speed regardless of actual engine temperature

Potential Causes

The most common technical causes for Code P944 on used Sany excavators include:

• Damaged or corroded wiring harness between the ECT sensor and ECM, particularly at known rub points near the engine firewall or along the chassis rail
• Failed Engine Coolant Temperature sensor due to internal element degradation or thermal cycling fatigue
• Corroded or loose connector pins at the sensor plug, causing intermittent high-resistance connections
• ECM internal circuit failure (less common), affecting the 5-volt reference voltage supply to the sensor
• Coolant contamination or air pockets affecting sensor contact with coolant, creating false readings

How to Troubleshoot and Fix Code P944

Step 1: Visual Inspection Begin by locating the ECT sensor (typically threaded into the engine block or thermostat housing). Inspect the wiring harness from sensor to ECM for obvious damage, chafing, or oil contamination. On used excavators, pay special attention to harness routing near moving engine components and areas where vibration causes wire-to-frame contact.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to measure sensor resistance. At room temperature (68°F/20°C), resistance should typically read 2,000-3,000 ohms (consult Sany specifications). Test the harness continuity and check for shorts to ground. Verify the ECM supplies proper 5-volt reference voltage at the disconnected harness connector.

Step 3: Component Replacement and Verification If sensor resistance is out-of-specification or harness shows high resistance/shorts, replace the faulty component. Clean all connector pins with electrical contact cleaner and apply dielectric grease. After repairs, clear codes using Sany diagnostic software or compatible scan tool, then operate the machine through a full heat cycle to confirm the fault does not return.

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Disclaimer: This guide provides general troubleshooting information. Always consult Sany service manuals and qualified diesel technicians for machine-specific procedures. Improper diagnosis can lead to expensive component damage.