Fuel control failure detection based on post O2 sensor

摘要

An engine diagnostic system includes a catalytic converter and an outlet O2 sensor. The outlet O2 sensor generates an outlet signal that is based on an oxygen level of exhaust gases exiting the catalytic converter. A controller adjusts a secondary fuel trim based on the outlet signal. The controller indicates a fault status if the secondary fuel trim has achieved a fuel trim limit and the outlet signal is out of a diagnostic range.