Exhaust gas after treatment system examining method for internal-combustion engine i.e. diesel engine, of motor vehicle, involves determining cause for excess of emission limit value based on comparison of number with threshold value

摘要

The method involves determining exceedance of an emission limit value, and changing quantity to be dosed of a reducing agent. A measured value is determined by using an exhaust sensor, and a characteristic number is computed, where the number includes the measured value. Cause for exceedance of the emission limit value is determined based on comparison of the characteristic number with a test threshold value and on the dosage of the agent, where hydro carbons are can be used as the reducing agent. An independent claim is also included for a device for examining an exhaust gas after treatment system.