Coolant temperature sending unit – check and replacement
Warning: Wait until the engine is completely cool before beginning this procedure.
Check
1. 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 by this manual, the Engine Coolant Temperature (ECT) sensor, which is an information sensor for the Powertrain Control Module (PCM), also functions as the coolant temperature sending unit (see Emissions and engine control systems).
2. If an overheating indication occurs, check the coolant level in the system and make sure all connectors in the wiring harness between the sensor and the indicator light or gauge are tight.
3. When the ignition switch is turned to START and the starter motor is turning, the indicator light (if equipped) should come on. This doesn’t mean the engine is overheated; it just means that the bulb is good.
4. 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.
5. 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, check for any stored trouble codes in the PCM (see Emissions and engine control systems).
6. If the engine tends to overheat easily, check the coolant to make sure it’s correctly mixed (see Tune-up and routine maintenance).
Replacement
7. See Chapter Emissions and engine control systems for the ECT sensor replacement procedure.