What is Sany Excavator Fault Code P153?

Fault Code P153 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) triggers when the Engine Control Module (ECM) receives a voltage reading outside the expected range from the coolant temperature sensor, typically above 4.8-4.9 volts when normal operating range should be 0.5-4.5 volts.

For Sany excavators, this code is critical because the ECM relies on accurate coolant temperature data to manage fuel injection timing, idle speed control, and engine protection protocols. When P153 is active, the ECM defaults to a predetermined temperature value, which can compromise engine efficiency and potentially cause overheating or poor cold-start performance on used machines with existing wear.

Common Symptoms

• Check Engine Light or Engine Warning Lamp illuminated on the instrument cluster
• Engine running in limp mode or experiencing power derate, especially noticeable during high-load digging operations
• Hard starting when the engine is cold, or excessively long cranking times
• Cooling fan running continuously at maximum speed regardless of actual engine temperature
• Rough idle or irregular engine RPM fluctuations, particularly during warm-up cycles

Potential Causes

The most common technical causes for P153 on used Sany excavators include:

• Open circuit in the ECT sensor wiring harness, often caused by wire chafing near the engine block mounting points or valve cover
• Failed coolant temperature sensor due to internal element degradation (common after 5,000+ operating hours)
• Corroded or loose connector pins at the ECT sensor plug, especially on machines exposed to harsh environmental conditions
• Damaged ECM wiring or poor ground connections affecting sensor signal return path
• ECM internal fault (rare, but possible on high-hour used equipment with electrical system history)

How to Troubleshoot and Fix Code P153

Step 1: Visual Inspection Begin by locating the ECT sensor (typically mounted on the engine block or cylinder head near the thermostat housing). Inspect the wiring harness for obvious damage, abrasion points where wires contact metal surfaces, or evidence of rodent damage. On used excavators, pay special attention to harness routing near moving engine components and check all connector terminals for corrosion, moisture intrusion, or bent pins.

Step 2: Electrical Testing Disconnect the ECT sensor connector and use a digital multimeter (DMM) to measure resistance across the sensor terminals. At room temperature (68°F/20°C), resistance should typically read 2,000-3,000 ohms; consult your Sany service manual for exact specifications. Next, check for continuity between the sensor signal wire and ECM pin (refer to wiring diagrams). Measure voltage at the disconnected harness connector with ignition on—you should see approximately 5 volts reference voltage from the ECM.

Step 3: Component Replacement and Verification If sensor resistance is out of specification or the wiring shows an open circuit, replace the faulty component. For used excavators, always apply dielectric grease to connector pins during reassembly to prevent future corrosion. After repairs, clear the fault code using Sany diagnostic software or a compatible OBD-II scanner, then monitor coolant temperature readings during a complete warm-up cycle to verify proper sensor operation and confirm the code does not return.

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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 high-voltage systems on construction equipment.