Method for monitoring sensor signals and quantitative determining of the stoichiometric fuel-air ratio of the type of fuel used by means of an injector test and catalyst diagnosis in a vehicle

Abstract

A method for the onboard diagnosis in a vehicle having a catalytic convertor and a lambda-controlled internal combustion engine in the running operation of the vehicle, includes determining the currently maximum possible oxygen storage capacity of the catalytic convertor as well as a measured temporal duration between the lean spike of the pre-catalyst lambda probe and the post-catalyst lambda probe takes place by means of an OSC diagnosis. The method also includes determining a theoretical residual oxygen content and determining a theoretical temporal duration. When the quotient between the measured temporal duration (Δt) and the theoretical temporal duration (Δt) lies within a predefined range delimited by a first and a second threshold value (SW; SW), thus: it is determined that the pre-catalyst lambda probe and the post-catalyst lambda probe operate without flaw.