An EGR (Exhaust Gas Recirculation) temperature sensor is an electrical sensing probe that is installed in the EGR passage between the EGR valve and the intake manifold. It is connected to the THG terminal on the ECM (engine control module). When the EGR valve opens, temperature increases. From the increase in temperature, the ECM knows the EGR valve is open and that exhaust gases are flowing. As the EGR system flows hot exhaust, the probe heats up and sends a signal to the computer that verifies that operation of the EGR system. The following schematic shows a typical circuit diagram of the Exhaust Gas Recirculation (EGR) Temperature Sensor.