Engine Coolant Temperature (ECT) Sensor

ECT sensor is a Negative Temperature Coefficient (NTC) sensor. Electrical resistance becomes less as temperature increases. ECT sensor may have a 2 or 4 pin connector. If ECT sensor has a 2 pin connector, sensor has one temperature sensing circuit. If ECT sensor has a 4 pin connector, sensor has 2 temperature sensing circuits. On 4 pin connectors, terminals No. 1 and 4 are for ME-SFI control module, terminals No. 2 and 3 are for automatic air conditioning control module.