The efficiency of the triple-acting catalytic converter is optimal if the engine operates in a narrow range of stoichiometric values (stoichiometry is the science of weight relationships) of the air-fuel mixture composition, designated lambda = 1. The lambda criterion then provides information on the relationship between the actual value of the air-fuel mixture composition and the stoichiometric value. From here it can be established whether there is an excess of free oxygen in the exhaust gases, which indicates a lean mixture. The ceramic material of the lambda probe is permeable to oxygen ions at a temperature of at least 300°C. The outer surface of the ceramic is in the exhaust gases, while the reference gas is inside. The difference in oxygen ion concentrations generates a signal proportional to the oxygen content in the exhaust gases. In the control unit, this signal is used to change the injection duration so that the mixture ratio constantly fluctuates around the value of lambda = 1 (0.98–1.02). Adjust CO content manually (carbon monoxide) impossible. Lambda probe (oxygen probe) is located in the exhaust pipe near the catalytic converter. After starting the engine, the lambda probe quickly warms up and starts working. In the absence of a signal from the lambda probe until it is connected, the control unit works with the simulated values. Its own diagnostics monitor the electrical part of the lambda probe, whether the signal has the appropriate values, or whether the lambda adjustment is within the specified parameters.
Additional signals
In addition to information from sensors and information transmitted from actuators, the control unit also generates so-called additional signals. They represent information received from other control units of the vehicle.