What are the common faults of the coolant temperature sensor?
3 Answers
The common faults of the coolant temperature sensor are short circuit, open circuit, or its output signal voltage does not match the standard. More information about the coolant temperature sensor is as follows: Since the accuracy of the coolant temperature sensor has a significant impact on the fuel injection volume, when the air-fuel mixture is too rich or too lean, the coolant temperature sensor should be inspected and removed. The method is: 1. Disconnect the wiring harness plug of the coolant temperature sensor and remove the sensor. 2. Place the coolant temperature sensor in a beaker of water, heat the water in the beaker, and measure the resistance between the two terminals of the sensor at different temperatures. 3. Compare the measured resistance value with the standard. If it does not meet the standard, replace the coolant temperature sensor.
An old car enthusiast recently asked me about the coolant temperature sensor, and I told him it can be a real headache when this thing fails. The most common issue is the sensor itself malfunctioning—either due to internal short circuits, broken wires, or aging components, causing the dashboard temperature gauge needle to jump erratically. Then there are wiring problems; those connecting wires are exposed to the high-temperature engine bay, and over time, the connectors oxidize or the wires wear out, leading to poor contact. Even worse is when coolant leaks corrode the sensor socket, or the fan spins wildly without stopping—definitely a sign of distorted signals. Last month, I encountered a case where the owner complained about a sudden spike in fuel consumption, and upon inspection, we found the sensor was completely coated with scale, falsely reporting low temperatures and causing the engine to continuously inject excess fuel. My advice is to check for loose connectors if you notice abnormal coolant temperature readings and replace the sensor entirely if necessary.
The mechanic at the repair shop taught me how to identify a faulty coolant temperature sensor, and there are three key symptoms to watch for. The first is inaccurate temperature readings on the dashboard, where the needle stays stuck at the lowest point or falsely indicates overheating. The second type of fault directly triggers a chain reaction: a sensor falsely reporting low temperature can cause the ECU to over-supply fuel, leading to cold start difficulties and black smoke from the exhaust pipe. Signal disruptions can also interfere with the cooling system, preventing the fan from turning on when it should, which may cause the radiator to overheat. The third type of hazard lurks in places you can't see, such as aging wiring with poor connections that can easily short-circuit on rainy days. Once, while driving on the highway, I noticed the temperature gauge suddenly malfunctioned. After pulling over, I found the sensor connector filled with green oxidation. Remember to regularly clean the wiring harness connectors in the engine bay—this simple method can prevent a lot of trouble.
