Oxygen Sensor for CNG Application as ULEV or Tighter Emission Vehicle

Two distinctive λ sensors have been developed for a compressed natural gas (CNG) vehicle that complies with OBD-II.

As the upstream sensor, there is employed an element which obtains an additional catalyst coating layer to enhance combustion of CH₄ and H₂ that reaches to the surface of the element. Meanwhile, as the downstream sensor, there is employed an element having an electrode that is intentionally inactive with CH₄, to eliminate the temperature dependent chemical reaction of CH₄ remaining after the catalyst converter, and to avoid false catalyst monitoring.

Use of the above two kinds of λ sensors enables construction of an O₂ feedback system for a CNG engine that complies with OBD-II.