Patent ID: 7665295

Claim:
A method for operating an internal combustion engine in whose exhaust-gas region an exhaust-gas treatment device is situated, comprising: introducing a reagent into the exhaust-gas region upstream in front of the exhaust-treatment device; immediately and directly spraying the reagent into the exhaust-gas region, wherein in a flow direction of the reagent, which is brought to a predefined reagent source pressure, a switchable reagent safety valve is arranged first and then a continuous reagent dosing valve, the reagent dosing valve being disposed in the exhaust-gas region; recording a reagent pressure in a reagent path, the reagent path being between the reagent safety valve and the reagent dosing valve; comparing the reagent pressure detected in at least one predefined state of at least one of the reagent safety valve, and the reagent dosing valve, to at least one threshold value, wherein the comparing step includes: a first checking step including checking whether the reagent pressure is just below the reagent source pressure, minus a pressure drop at the reagent safety valve when the reagent safety valve and the reagent dosing valve are open simultaneously; and a second checking step including checking whether the reagent pressure is above an exhaust-gas pressure and below the reagent source pressure, minus the pressure drop at the reagent safety valve following a closing of the reagent safety valve subsequent to the first checking step and a closing of the reagent dosing valve subsequent to the first checking step; and providing a fault signal in case of a threshold exceedance.