Can you double check that error code. I can find no reference to that code which would indicate that it'* not proper.

The O2 sensor is in the rear exhaust manifold. Look down between the engine and firewall about in the middle.



With the miles on your car, if the O2 sensor hasn't been changed, it wouldn't hurt to change it even if it'* not the problem.

P0402

AllData:

"This code is not a valid code for this vehicle." :?

I apologize, the code was not P0402, it is P0420, Catalyst System Efficiency Below Threshold (Bank 1) I typed it wrong last night.

420 is the REAR 02 sensor which is in the exhaust right after the Cat. Either your cat is bad and not functioning or your rear 02 sensor needs replaced.

Thanks Rogue. I hope this will solve the problem, I will take care of this in a week or two. Do you think I should go ahead and replace both? The converter was replaced back in Jan. 06 and they did not replace either sensor.

How many miles on the car? The rear 02 has no bearing on fueling and you can actually leave it bad if you don't mind the code. The front 02 should ocillate low high quickly at idle, if its lazy or doesnt switch then it should be replaced. You can check this with a scanner.

It has 116,000 miles and runs great! I would just leave it alone but I will have an emissions inspection in 3 months and it won't pass with the light on.

In that case, you should consider replacing the rear O2 sensor.

I'm not a huge fan of replacing both "just because they're old", but it'* really your call and what you are comfortable with. Your PCM is pretty sensitive and will usually let you know when you have a problem.

On the other hand, I also prefer to repair things that keep the SES light on. Ignoring them allows other things to go wrong with no indication to you. Use the SES/CEL as a tool as it was designed, especially since you have no scanner (or really a need for one).

Thanks everyone, I will tackle it in a couple of weeks when my schedule permits and will post results.