Method and apparatus for identifying characteristic shift downward

摘要

A system for detecting a fault in an exhaust gas oxygen (EGO) sensor includes generating a first signal with a first voltage if the EGO sensor output signal is approaching an unacceptable voltage and a second voltage if the EGO sensor output signal has an unacceptable voltage. The system further includes setting a first flag if the first signal has the first voltage and a second flag, indicating an EGO sensor fault, if the first signal has the second voltage and the first flag is set.