Misfire Monitor
WARNING: This page is about a different car, the 2015 RAM ProMaster 3500, 2015 RAM ProMaster 2500, and 2015 RAM ProMaster 1500. However, it is still accessible from the selected car via links, so may be relevant.
Excessive engine misfire results in increased catalyst temperature and causes an increase in HC emissions. Severe misfires could cause catalyst damage. To prevent catalytic convertor damage, the PCM monitors engine misfire.
The Powertrain Control Module (PCM) monitors for misfire during most engine operating conditions (positive torque) by looking at changes in the crankshaft speed. If a misfire occurs the speed of the crankshaft will vary more than normal.