In electronic injection systems, catalysts work correctly only if the ratio between the weight of the intake air and the weight of the injected petrol is correct, which is 14.7 parts air to 1 part gasoline: this ratio is called "stoichiometric" or l (lambda).

The lambda sensors are sensors used to detect the presence of oxygen in the exhaust manifold of endothermic engines, thus enabling real-time correction of the stoichiometric ratio, allowing the catalytic converters to function properly and eliminating harmful exhaust gases.