Theory Of Operation

The Exhaust Gas Recirculation (EGR) Temperature Sensor is positioned between the EGR Cooler and EGR Valve. The feedback signal from the sensor is used to monitor the cooling efficiency of the recirculated exhaust gases passing through the EGR Cooler Assembly. At lower temperatures the signal feedback voltage will read closer to the upper operating parameter. As the recirculated exhaust gas temperature increases, the signal feedback voltage will decrease toward the lower operating parameter.

There is a sensor rationality monitor that runs after a cold soak condition, at initial engine start up. When certain enable conditions are met, the Powertrain Control Module (PCM) will compare the EGR Temperature Sensor reading to the Engine Coolant Temperature (ECT), Ambient Air Temperature (AAT) Sensor readings for plausibility.

A second monitor will run when the EGR system is active to monitor the sensor plausibility. It works as follows: There is a small voltage difference between the upper operating parameter and the voltage threshold that will set a circuit high fault. The same is also true for the lower operating parameter and the voltage threshold that will set a circuit low fault. These small voltage windows are used for checking the coherency of the sensor. If the signal voltage reads in one of these windows, a sensor circuit performance fault will set.