Circuit Description

ECT sensor uses a thermistor to control signal voltage to PCM. PCM applies and monitors a 5-volt reference signal to sensor. When engine coolant is cold, sensor (thermistor) resistance is high and PCM will sense a high signal voltage. As engine coolant warms, sensor resistance becomes less and PCM voltage drops. With Code P0118 set, PCM will turn cooling fans on and use a default engine coolant temperature value based on run time.