Engine Oil Temperature

Engine Oil Temperature

The engine oil temperature (EOT) sensor (Figure 28) is a thermistor device in which resistance changes with temperature. The electrical resistance of a thermistor decreases as the temperature increases and increases as the temperature decreases. The varying resistance affects the voltage drop across the sensor terminals and provides electrical signals to the PCM corresponding to temperature.

Thermistor-type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow.

Voltage that is dropped across a fixed resistor in a series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor.

The EOT measures the temperature of the engine oil. The EOT sensor is similar in construction to the engine coolant temperature (ECT) sensor. On some applications, EOT input to the PCM is used to initiate a soft engine shutdown. This prevents engine damage from occurring as a result of high oil temperature.

Figure 28: Engine Oil Temperature (EOT) Sensor: