Theory of Operation
WARNING: This page is about a different car, the 2011 RAM Pickup. However, it is still accessible from the selected car via links, so may be relevant.
The Crankcase Pressure Sensor is used to monitor the pressure inside the crankcase. The Powertrain Control Module (PCM) supplies the crankcase pressure sensor a 5-Volt reference voltage. When the crankcase pressure is low, the sensor signal voltage is low. When the crankcase pressure is high, the sensor signal voltage is near the 5-Volt reference voltage. The PCM monitors the crankcase pressure signal circuit voltage to calculate the pressure of the air within the crankcase. The PCM will illuminate the MIL lamp after the monitor runs and fails in two consecutive trips.