A method to determine the mass flow rate of a low-pressure exhaust gas recirculation EGR circuit (EGR LP ) of an internal combustion engine (1) comprising a first linear sensor (30) to measure the quantity of oxygen available in the mixture of fresh air taken in and exhaust gases flowing through the intake pipe (6) and a second linear sensor (25) to measure the quantity of oxygen available in the flow of exhaust gases; the method comprises the steps of determining a control current (I) of the first sensor (30) and a control current (I) of the second sensor (25); in case the flow of exhaust gases in rich in fuel, updating the control current (I) of the first sensor (30) as a function of the control current (I) of the second sensor (25); and determining the mass flow rate of a low-pressure exhaust gas recirculation EGR circuit (EGR LP ) as a function of the control current (I) of the first sensor (30) and a control current (I).
