EGR Temperature Sensor: Description and Operation

PURPOSE
The EGR temperature sensor converts the temperature of EGR gas downstream from the EGR valve to voltage and inputs it to the engine control module. The engine control module judges the condition of the EGR by this signal. If there is abnormal condition, the check engine/malfunction indicator lamp is turned on to notify the driver.

OPERATION
5 volts power supply in the engine control module is applied to the EGR temperature sensor through the resistance in the unit. This power supply further passes through the EGR temperature sensor, which is a kind of a resistor, and is grounded at the engine control module. The resistance of the EGR temperature sensor is characterized by a decrease in resistance with an increase of EGR temperature due to increase in quantity of EGR. EGR temperature sensor terminal voltage increases or decreases in accordance with EGR temperature sensor resistance. Therefore, the EGR temperature sensor terminal voltage changes with EGR gas temperature. The higher the EGR gas temperature, the lower the EGR temperature sensor terminal voltage.

CONSTRUCTION
The sensor is a resistor that decreases in resistance as temperature increases.