Circuit Description

Engine Coolant Temperature (ECT) sensor is a thermistor located in lower coolant passage in cylinder head. ECT sensor resistance is high when coolant temperature is cold and resistance drops when coolant temperature increases. PCM provides a 5-volt reference and a ground signal to ECT sensor. PCM reads voltage drop on the signal line to determine coolant temperature. ECT sensor is used for fuel/ignition control, hot/cold coolant light, temperature gauge and cooling fan.

DTC P0125 will set if coolant temperature is less than 32°F (0°C) after engine has been running for more than 5 minutes when no ECT and IAT DTCs have been set. ECT signal is continuously monitored when engine is running.