Method in a vehicle computer for checking an exhaust gas coding selected in a vehicle, wherein an exhaust gas coding is respectively assigned to an exhaust gas standard from a group of exhaust gas standards comprising a first exhaust gas standard and at least one second exhaust gas standard, wherein the first exhaust gas standard and the at least one second exhaust gas standard are stored in the vehicle computer and determine the control of the internal combustion engine by an engine control unit and define routines of on-board diagnostics for monitoring a function of the exhaust gas system, having the steps of: (a) reading in a first digit or a first group of digits of a computer-readable vehicle identification number stored in the vehicle computer, reading in a second digit or a second group of digits of the vehicle identification number and reading in a third digit or a third group of digits of the vehicle identification number, (b) providing a computer-readable characteristic map which is stored in the vehicle computer and assigns those characteristic values of the third digit or third group of digits of vehicle identification numbers which indicate a vehicle belonging to the first exhaust gas standard to the first digit or first group of digits and to the second digit or second group of digits of the vehicle identification number, (c) comparing the read-in third digit or third group of digits of the vehicle identification number with that characteristic value from the characteristic map which is assigned to the read-in first digit or first group of digits and to the read-in second digit or second group of digits of the vehicle identification number, (d) determining whether or not the vehicle belongs to the first exhaust gas standard on the basis of determined correspondence or lack of correspondence between the characteristic value of the characteristic map and the read-in third digit or third group of digits of the vehicle identification number, (e) if it is determined in step (d) that the vehicle belongs to the first exhaust gas standard, comparing whether an exhaust gas standard selected in the vehicle computer corresponds to the first exhaust gas standard, and (f) if it is determined in step (e) that the selected exhaust gas coding does not correspond to the determined first exhaust gas standard, carrying out at least one of the following measures: selecting and using the first exhaust gas standard in the vehicle computer in order to prevent the vehicle from being incorrectly operated with a less strict exhaust gas standard than the first exhaust gas standard, or preventing a starting clearance, as a result of which the vehicle cannot be started and moved, wherein the following measure can be additionally carried out: generating an error signal by storing an error entry in an error memory of the vehicle. (a) reading in a first digit or a first group of digits of a computer-readable vehicle identification number stored in the vehicle computer, reading in a second digit or a second group of digits of the vehicle identification number and reading in a third digit or a third group of digits of the vehicle identification number, (b) providing a computer-readable characteristic map which is stored in the vehicle computer and assigns those characteristic values of the third digit or third group of digits of vehicle identification numbers which indicate a vehicle belonging to the first exhaust gas standard to the first digit or first group of digits and to the second digit or second group of digits of the vehicle identification number, (c) comparing the read-in third digit or third group of digits of the vehicle identification number with that characteristic value from the characteristic map which is assigned to the read-in first digit or first group of digits and to the read-in second digit or second group of digits of the vehicle identification number, (d) determining whether or not the vehicle belongs to the first exhaust gas standard on the basis of determined correspondence or lack of correspondence between the characteristic value of the characteristic map and the read-in third digit or third group of digits of the vehicle identification number, (e) if it is determined in step (d) that the vehicle belongs to the first exhaust gas standard, comparing whether an exhaust gas standard selected in the vehicle computer corresponds to the first exhaust gas standard, and (f) if it is determined in step (e) that the selected exhaust gas coding does not correspond to the determined first exhaust gas standard, carrying out at least one of the following measures: selecting and using the first exhaust gas standard in the vehicle computer in order to prevent the vehicle from being incorrectly operated with a less strict exhaust gas standard than the first exhaust gas standard, or preventing a starting clearance, as a result of which the vehicle cannot be started and moved, wherein the following measure can be additionally carried out: generating an error signal by storing an error entry in an error memory of the vehicle. selecting and using the first exhaust gas standard in the vehicle computer in order to prevent the vehicle from being incorrectly operated with a less strict exhaust gas standard than the first exhaust gas standard, or preventing a starting clearance, as a result of which the vehicle cannot be started and moved, wherein the following measure can be additionally carried out: generating an error signal by storing an error entry in an error memory of the vehicle.