Abstract: The invention relates to a method for diagnosing the performance of a catalytic converter (3) of a petrol automobile onboard the vehicle, the catalytic converter being mounted on the exhaust line (1) of the vehicle, wherein said method comprises placing two oxygen probes (5, 6) on the exhaust line (1) upstream and downstream from the converter (3), respectively, analysing the signals (7, 16) thereof, and comparing the signal (16) of the downstream probe (6) with a threshold in order to carry out a passive diagnosis during a first period of the lifespan of the converter (3), after which, during a last period of the converter (3) lifespan, an intrusive diagnosis of the converter (3) performance is carried out using the two probes (5, 6) and a diagnosis automaton, by measuring the oxygen storage capacity of the converter (3).

Abstract: The invention relates to a method for diagnosing the performance of a catalytic converter (3) of a petrol automobile onboard the vehicle, the catalytic converter being mounted on the exhaust line (1) of the vehicle, wherein said method comprises placing two oxygen probes (5, 6) on the exhaust line (1) upstream and downstream from the converter (3), respectively, analysing the signals (7, 16) thereof, and comparing the signal (16) of the downstream probe (6) with a threshold in order to carry out a passive diagnosis during a first period of the lifespan of the converter (3), after which, during a last period of the converter lifespan, an intrusive diagnosis of the converter (3) performance is carried out using the two probes (5, 6) and a diagnosis automaton, by measuring the oxygen storage capacity of the converter (3).