The coolant temperature indicator system consists of a dashboard warning light or gauge and a coolant temperature sending unit mounted on the engine. The Engine Coolant Temperature (ECT) sensor also serves as the coolant temperature sending unit. When overheating is indicated, examine the level of coolant and check that all wiring connectors are tight. The ignition switch has to be turned to START for the indicator light to come on and show that it works. If the light does not come on, then there could be several explanations such as a defective bulb or an issue with either the ignition switch or circuit. After that moment when the engine starts operating, it should go off unless something goes wrong like overheating. It shall remain so if there is an earth defect, faulty sending unit, or ignition switch that does not work properly.