06 caravan, 88000 miles. engine light drew a p0420 code after changing my radiator two days earlier myself. the engine never got hot, nor really low on coolant. I caught it early.

does that code necessarily mean the rear 02 sensor, or front sensor if i chose to replace one of the two sensors as a means to correct issue. the engine light came on 5 minutes after i went from 30 to 45mph as quick as i could.

i don't want to just change parts but won't pay the cost for a catalytic converter if that comes up. what sensor would you change if you were to change one of the two sensors?

 

Catalyst below efficiency threshold. Downstream sensor. I'd replace it, reset the code and see if it comes back.

 

Well almost. I would reset the code first and see if it comes back. They don't sometimes.

http://www.obd-codes.com/p0420

 

True. ^^

 

I thank each of you for responding to me quickly. i will pull the negative lead off battery to reset, maybe turn head lights on for 5 minutes to drain any settings. saw that on youtube.

hopefully it will stay off. have only 88,000 miles on it.

from what i read catalytic inefficiency doesn't cause any mechanic issues.
i do know a upstream sensor thats bad causes rick or lean fuel mixture leading to rapidly poor gas mileage.