The coolant temperature indicator system consists of a warning light or a temperature gauge on the dash and a coolant temperature-sending unit mounted on the engine. On the models covered, the Cylinder Head Temperature (CHT) sensor (V8 models)or Engine Coolant Temperature (ECT)sensor(V6 models), which is an information sensor for the Powertrain Control Module (PCM), also functions as the coolant temperature sending unit. If an overheating indication occurs check the coolant level in the system and make sure all connectors in the wiring harness between the sending unit and the indicator light or gauge are tight. When the ignition switch is turned to start and the starter motor is turning, the indicator light (if equipped) should come this doesn't mean the engine is overheated; it just means that the bulb is good. If the light doesn't come on when the ignition key is turned to START the bulb might be burned out, the ignition switch might be faulty or the circuit might be open. As soon as the engine starts, the indicator light should go out and remain off, unless the engine overheats. if the light doesn't go out, the wire between the sending unit and the light could be grounded, the sending unit might be defective, or the ignition switch might be faulty. Check the coolant to make sure it's correctly mixed; plain water. with no antifreeze, or coolant that's mainly water, might have too low a boiling point to activate the sending unit.
