To replace the coolant temperature sensor in a Toyota Yaris, drain the coolant from the system, check the condition of the coolant, flush it if necessary, and then remove the old sensor before installing the new one. When the new sensor is in, fill the system with coolant.
When draining the coolant from the cooling system to begin the repair, the tank does not have to be empty. Instead, as long as the coolant level is below the sensor, that is enough. With the coolant out of the tank, check the condition of the substance. If it is more than three to five years old, depending on the type of coolant, replace it. Also, replace the coolant and flush the system if there are any signs of debris or contamination.
Remove the old sensor, and before putting the new sensor in, coat it with a sealer to prevent any leaks; then, tighten the sensor into place. When the new sensor is in place, begin refilling the cooling system. Make sure that the system does not contain any air before closing it. If there is air in the system, it can cause the engine to overheat, or the coolant sensor may not register correctly. If this occurs, the car's check engine light appears.