How to Determine if the Coolant Temperature Sensor is Faulty?
2 Answers
If the diagnostic tool displays a fault code for the coolant temperature sensor, it indicates that the sensor is faulty. However, it is important to note that the inspection should be performed when the engine is cold. Use a multimeter to test the sensor, and then heat the coolant temperature sensor with a hair dryer. If the resistance value does not change, it means the coolant temperature sensor is already damaged.
Last time my car's temperature gauge was fluctuating, so I went straight to my friend's repair shop for a check. The experienced mechanic told me to start the engine cold first and observe if the temperature gauge showed normal low temperature; after the car warmed up, the needle should stabilize in the middle range. If it always showed low temperature or suddenly spiked to the red line, it was most likely a sensor issue. He used a diagnostic tool to detect fault code P0118, and the data stream showed erratic temperature readings, while the actual radiator temperature felt normal. Later, he removed the sensor and tested its resistance in warm water, finding that the resistance didn't change with temperature, confirming it was faulty. The mechanic said a faulty sensor could also cause a spike in fuel consumption because the engine control unit would mistakenly increase fuel injection.
