It is important for the coolant temperature sensor to be functional at all times or else it won’t be able to properly determine the temperature of the coolant inside an internal combustion engine. The information about the temperature that’s detected by the sensor is sent to the engine control unit. From there, the engine control unit makes adjustments to the ignition timing and fuel injection based on the data it received from the sensor. If there is a problem with the sensor then it will decrease your fuel mileage and cause your car to overheat; amongst other things. Fortunately, the symptoms of a failing coolant temperature sensor are easy to spot.
Poor fuel economy is a major symptom of a failing coolant temperature sensor. What happens is the failing sensor will send a bad signal to the engine control unit which will then throw off the calculations for the amount of fuel it needs and the timing of the fuel injections. This will result in more fuel being injected than is actually needed. In other words, your car will burn up more fuel than is necessary which means you’ll have to purchase gas more frequently. Another symptom you may experience is black smoke coming out of your car’s exhaust pipe. This occurs when the bad signal causes the computer to excessively mix the fuel with the air. As a result, the fuel is unable to get burned when it reaches the combustion chamber. Instead, it burns up as it passes into the exhaust pipes, which causes black smoke to come out. The black smoke will continue to come out until you replace the sensor.
Like previously mentioned, your engine can overheat if your coolant temperature sensor malfunctions. This malfunction will send a signal which tells the engine control unit to heat up rather than cool off. When this happens, they’ll be ignition misfires and engine overheating. You may even see the “Check Engine” light turn on from your dashboard area. Newer cars are programmed to turn this light on when a problem with the sensor’s signal is detected. Of course, you should always be cautious when you see any kind of engine light turn on. In any case, bring your vehicle to the nearest auto mechanic and have them inspect your engine right away. They’ll most likely tell you that you have a problem with your coolant temperature sensor, assuming there’s nothing else wrong with your vehicle’s engine.