Circuit Description

ECT sensor is a thermistor mounted on a coolant crossover pipe at front of engine. PCM applies about 5 volts through a pull-up resister to ECT signal circuit. When engine coolant is cold, sensor (thermistor) resistance is high and PCM will monitor a high signal voltage. As engine coolant warms, sensor resistance becomes less, engine coolant temperature measured at PCM drops. With a fully warmed-up engine, ECT signal voltage should measure about 1.5-2.0 volts.