Theory Of Operation

WARNING: This page is about a different car, the 2014 RAM 1500. However, it is still accessible from the selected car via links, so may be relevant.

The Powertrain Control Module (PCM) uses a Fuel Mass Observer (FMO) Monitor to check the injection correction quantity for exceeding permissible limits and the fuel mass over a period of time. The FMO activation time monitor checks time to enter closed loop air/fuel ratio control diagnosis. The O2 sensor output is used to calculate the total system error represented as the quantity which is used for correction of the O2 Sensor signal. The controller keeps adjusting the O2 Sensor model until it follows the measured O2 signal (the difference converges to zero). The described rationality check will detect fuel injection quantity too low or too high, system too lean or too rich, and excessive time to enter closed loop air/fuel ratio control failure.