Patent ID: 7582480

Claim:
A process for diagnosing the oxidation capacity of a catalytic converter processing exhaust gases of a heat engine by means of a trap which stores and then reduces the nitrogen oxides (NOx) contained in these gases, the process comprising the steps of: determining the oxygen (O 2 ) content of the exhaust gases downstream of the trap by means of a sensor located downstream from the trap, and determining, from a level of a lambda ON/OFF signal emitted by the sensor, a decrease in the oxidation capacity of the trap, wherein the decrease in the oxidation capacity of the trap is determined by detecting a reduction of the hydrocarbon oxidation rate of the trap (i) during a regeneration phase in rich mode and (ii) after a phase of removal of nitrogen oxides (NOx) stored in the trap has substantially ended, wherein the reduction of the hydrocarbon oxidation rate is detected by detecting a decrease in a maximum voltage of a lambda ON/OFF signal provided by a sensor located downstream of the trap (i) during a regeneration phase in rich mode and (ii) after a phase of removal of nitrogen oxides (NOx) stored in the trap has substantially ended, this maximum voltage being dependent on a quantity of non-oxidized hydrocarbons present in the exhaust gases downstream of the trap, such that a decrease in the maximum voltage of the lambda ON/OFF signal indicates a reduction of the hydrocarbon oxidation rate of the trap.