ECT, AF Sensor recap

By ADRIEL CHUNG

Engine Coolant Temp

Functionality

The engine coolant temperature needs to be monitored constantly for many different aspects of the vehicle. This sensor is what the ecm uses to tell when to exit (open loop) . The ecm also uses the coolant temp to tell the radiator fan when to come on. Along with those components the ecm also uses the ECT to turn off the Heater circuit for the 02 sensors when the vehicle is at operating temp. This sensor uses a 5v reference voltage to tell the EMC what the temp is.

​How are the sensors read and at what voltage?

O2 Sensors read in a voltage range from 0-1V. If this sensor is reading close to 1 our AF mixture is rich. Closer to 0 our mixture is LEAN.
A/F sensors read in a voltage range from 0-5V. If the sensor voltage is closer to 5 our AF mixture is lean. Closer to 0 our mixture is RICH.

A/F O2 Sensor Names

Depending on the position and type of sensor we are using that will change the terminology we use to designate those sensors.

If the sensor is an A/F sensor positioned before the Cat that is the (Upstream Wide Band)
If the sensor is an O2 Sensor placed after the cat it will be considered the (Down Stream Narrow Band)
O2 Sensors are Narrow band 0-1V
AF Sensors are Wide band 0-5V