The study includes attempts to identify separate mathematical functions for the rich and lean sides of a narrowband lambda sensor, with the goal of applying an algorithm to estimate the actual Air-Fuel Ratio (AFR) in a range other than stoichiometric. Subsequently, the aim is to force the engine\'s Powertrain Control Module (PCM) to operate in closed-loop mode at an AFR different from 1. A key aspect of the study is the use of a conventional narrowband lambda sensor, typically installed in older internal combustion engines. This approach could, for example, enable retrofitting of older engines or adapting them to operate on alternative fuels. The study also illustrates the physical characteristics of the sensor’s heater, aiming to optimize the algorithm for maintaining a stable sensor temperature, thereby improving reading accuracy and control quality