Catalytic converter diagnostic

摘要

A diagnostic for an internal combustion engine exhaust gas treatment means includes a series of enabling conditions for modelling temperature and operational stability of the treatment means and includes first and second stage tests alternately applied on an engine air/fuel ratio cycle-by-cycle basis in accord with the diagnosed performance of the treatment means using post-converter oxygen sensor information. When the treatment means performance is diagnosed as being degraded close to a failed condition, the first stage is disabled and the more statistically rigorous second stage is activated to closely scrutinize converter performance using a two phase approach for false alarm protection.