Are there separate computer analysis codes for oxygen sensors vs. the converter?. on 1999 Toyota Corolla

My engine light has been on continuously since late April. In June, the mechanic hooked the car up to a hand-held computer and said I needed a new cat. converter but didn't need to hurry fixing it as long as I did so before the inspection date. Last week, I went to a different service that hooked up the car to the computer and said it was the oxygen sensors.Their quote was $700 to fix them.but they've knocked in down to $500 when I squaked. Which scenario do you think is more likely?

by in Melrose, MA on September 14, 2009
1 answer
ANSWER by on September 14, 2009
What codes were stored? P0420 is low catalytic converter efficiency. Oxygen sensor codes can be for performance or heater circuit malfunction. A bad O2 sensor can make the computer think the cat converter is bad but I have replaced Cats on these cars as well.