1998 cavalier
rloya99
09-28-2007, 09:37 PM
i have a 98 cavalier with code PO420-catalyst efficiency below threshold (bank 1) thank u could anybody help
shakewell
09-28-2007, 10:17 PM
Either one of the O2 sensors is going bad or the cat is going bad.
rloya99
09-28-2007, 10:22 PM
thanks i will replaced them see it works
shakewell
09-29-2007, 12:19 AM
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.
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