An assembly for determining lambda values of an exhaust gas of an internal combustion engine is provided. The internal combustion engine is attached to an exhaust gas treatment device with at least one first catalyst and a second catalyst. Additionally, the assembly has the following: a first lambda sensor in a first removal line, wherein the first removal line is designed to remove a part of the exhaust gas upon entering the first catalyst and conduct same back into the exhaust gas treatment device after the exhaust gas passes the first lambda sensor, and the first lambda sensor and at least one part of the first removal line are arranged outside of the exhaust gas treatment device; and a second lambda sensor in a second removal line, wherein the second removal line is designed to remove a part of the exhaust gas between the first catalyst and the second catalyst and conduct same back into the exhaust gas treatment device after the exhaust gas passes the second lambda sensor, and the second lambda sensor and at least one part of the second removal line are arranged outside of the exhaust gas treatment device.