Theory of Operation

WARNING: This page is about a different car, the 2011 RAM Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

The Exhaust Gas Recirculation (EGR) Outlet Temperature Sensor is a variable resistor sensor and is used to measure the temperature of the EGR gas flow after it exits the EGR Cooler. The Powertrain Control Module (PCM) supplies 5-Volts to the exhaust gas recirculation temperature signal circuit. The PCM monitors the change in voltage caused by changes in the resistance of the sensor to determine the EGR outlet temperature. There are two rationality tests. Key-on and engine running. The key-on test fails if the EGR Outlet Temperature Sensor value is different than the key on temperature estimate by more than a calibrated threshold. The engine running test fails if the EGR Outlet Temperature Sensor value does not change by more than a calibrated threshold, over a calibrated period of time. If this fault becomes active the PCM will light the MIL light immediately. During this time the EGR valve will be closed. The PCM turns off the MIL when the diagnostic runs and passes in four consecutive drive cycles.