Theory Of Operation
WARNING: This page is about a different car, the 2014 RAM 3500 HD and 2014 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.
The fuel level is recorded by the Powertrain Control Module (PCM) when the ignition key is turned off, and is compared to the fuel level at the next ignition key on cycle. If the PCM recognizes a 25% increase in fuel level, the Leak Test Monitor is initiated. If the Large leak test fails it is determined that the Fuel Filler Cap is faulty or not installed properly, or the Capless Fuel Filler Assembly flap did not seal properly after fueling. A LOOSE GAS CAP message will be displayed on the cluster to inform the customer.