Patent ID: 8515710

Claim:
Method for identifying a fault in a temperature sensor present in a combination comprising a combustion engine having an exhaust gas treatment system that includes a catalyst chamber, said system including an upstream temperature sensor disposed in effective sensing contact with engine exhaust gases present prior to their entry into said catalyst chamber, and a downstream temperature sensor disposed in effective sensing contact with treated engine exhaust gases exiting said catalyst chamber, said method comprising: providing a first specified temperature and a second specified temperature; providing a diagnostic time period; providing a critical difference value; providing a timeout value; operating said engine; determining a first point in time that the temperature of said upstream temperature sensor reaches said first specified temperature; determining a second point in time that the temperature of said upstream temperature sensor reaches said second specified temperature; determining a third point in time at which the temperature reading provided by said downstream temperature sensor reaches said first specified temperature; determining a time interval, representing the amount of time elapsed between said first point in time and said third point in time; determining the difference between said time interval and said diagnostic time period; and indicating a fault condition for said downstream temperature sensor upon occurrence of at least one of the events selected from the group consisting of: the difference between said time interval and said diagnostic time period is greater than said critical difference value; and said downstream temperature sensor does not reach said first specified temperature prior to the elapse of an amount of time equal to said timeout value, as measured from said first point in time.