1998 cavalier

[rloya99]

i have a 98 cavalier with code PO420-catalyst efficiency below threshold (bank 1) thank u could anybody help

[shakewell]

Either one of the O2 sensors is going bad or the cat is going bad.

[rloya99]

thanks i will replaced them see it works

[shakewell]

Are you going to replaced all of those parts or just replaced the leased expensive ones? You could always just cleared the code and see if it comed back.