A method for determining a pressure in the output of an exhaust gas system of an internal combustion engine system of a vehicle, wherein the internal combustion engine system has: an internal combustion engine with a suction pipe and an exhaust gas output; a fresh air feed, which connects the suction pipe of the internal combustion engine with the environment; an exhaust gas system, which connects the exhaust gas output of the internal combustion engine with the environment; an exhaust gas turbo charger with a compressor arranged between the fresh air feed and the suction pipe and a turbine arranged between the exhaust gas output of the internal combustion engine and the exhaust gas system as well as a low pressure exhaust gas recirculation with a low pressure exhaust gas recirculation valve, which couples the fresh air feed with the output of the exhaust gas system, and the method comprises the steps: - detection of a mass flow through the internal combustion engine system, - detection of an ambient pressure at the fresh air feed of the internal combustion engine system, - determination of a throttling of the mass flow through the internal combustion engine system by means of a flow model of the internal combustion engine system, in which the following quantities are included: - an engine filling of the internal combustion engine, which is determined from a suction pipe pressure and a suction pipe temperature, - a fresh air mass flow in the fresh air feed, and - a mass flow in the low pressure exhaust gas recirculation, and - determination of the pressure deviating from the ambient pressure in the output of the exhaust gas system depending on the mass flow, the ambient pressure, the throttling of the mass flow through the internal combustion engine system and a position of the low pressure exhaust gas recirculation valve. an internal combustion engine with a suction pipe and an exhaust gas output; a fresh air feed, which connects the suction pipe of the internal combustion engine with the environment; an exhaust gas system, which connects the exhaust gas output of the internal combustion engine with the environment; an exhaust gas turbo charger with a compressor arranged between the fresh air feed and the suction pipe and a turbine arranged between the exhaust gas output of the internal combustion engine and the exhaust gas system as well as a low pressure exhaust gas recirculation with a low pressure exhaust gas recirculation valve, which couples the fresh air feed with the output of the exhaust gas system, - detection of a mass flow through the internal combustion engine system, - detection of an ambient pressure at the fresh air feed of the internal combustion engine system, - determination of a throttling of the mass flow through the internal combustion engine system by means of a flow model of the internal combustion engine system, in which the following quantities are included: - an engine filling of the internal combustion engine, which is determined from a suction pipe pressure and a suction pipe temperature, - a fresh air mass flow in the fresh air feed, and - a mass flow in the low pressure exhaust gas recirculation, and - an engine filling of the internal combustion engine, which is determined from a suction pipe pressure and a suction pipe temperature, - a fresh air mass flow in the fresh air feed, and - a mass flow in the low pressure exhaust gas recirculation, and - determination of the pressure deviating from the ambient pressure in the output of the exhaust gas system depending on the mass flow, the ambient pressure, the throttling of the mass flow through the internal combustion engine system and a position of the low pressure exhaust gas recirculation valve.