Theory Of Operation
WARNING: This page is about a different car, the 2013 RAM 3500 HD and 2013 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.
The Powertrain Control Module (PCM) continuously monitors the engine's fault code status to determine if any fault codes critical to successful engine operation are active. The PCM will illuminate the MIL Lamp immediately after the diagnostic runs and fails. The DTC will become inactive as soon as all active critical fault codes have been repaired.