Theory Of Operation

WARNING: This page is about a different car, the 2012 RAM Pickup. However, it is still accessible from the selected car via links, so may be relevant.

The Evaporative Purge Monitor tests the integrity of the hoses/tube between the throttle body/intake and the fuel tank. The monitor will be enabled under either a Small Leak test or it will run during a Large Leak test (This is when Small Leak test does not pass). During a Small Leak test, the monitor will first evaluate the delta pressure on the Fuel Tank Pressure (FTP) sensor while normal purge control is active. If the monitor does not pass within a calibrated amount of time, then an intrusive monitor will be enabled. This intrusive monitor will ramp in the purge flow to a target amount while evaluating the delta pressure in the entire system. If the delta pressure between purge off and purge on exceeds a calibrated amount, then the monitor will ramp out the purge flow and evaluate the delta pressure between the high flow and the new low flow target. If the delta pressure is less than a calibrated threshold then the monitor will pass.