I am getting this Catalyst efficiency lowbank1 and I just put in a new air intake. Could they both be related? Or is the problem with the O2 sensors or the catalytic converter??? Are there are any tests I can do to isolate it to one thing? Can the code tell me which o2 sensor is??The car has just one catalytic converter.
Once I reset the computer it takes a couple miles for the "check engine light" to show up again, I don't really know if that is relevant. Also the car is running fine as far as I can tell. Thanks in advance for the help!!!

I have been reading around the forum and I see that a lot of people can tell which o2 sensor is faulty from the code? Did the scanner they used at autozone crap or am I missing something?

 

P0420 - Catalyst System Efficiency Below Threshold (Bank 1)

Start there. This is not a code that directly indicates an issue with an O2 sensor.

 

Yeah I read that page and I was going the easiest way first which is to check out the o2 sensor before going into the catalytic converter. But how do I test the o2 sensors? There are 4 wires, one is ground, another is 12v and the other two I have no idea. Anybody know what the other two wired do and their colors? How could I check the cat converter?Taking it to a shop?Thanks for the help.

 

Also, does this mean that the code and the cold air intake have nothing to do with each other?

 

I highly doubt the two are related.

 

If you have to replace one O2 sensor replace them both. Its not worth the trouble it will eventually cause to do one only

 

ok I will do that. Is there any way I can test them before changing them? Thanks

 

Not sure how to test them. Ive only replaced an O2 sensor on an Intrepid. took it to a garage for the diagnostic then did the work myself. It fixed the problem i was having with that car.

 

ok so get this. I get from work turned the car off and then turned it back on once I was ready to test the sensors 5 minutes later so it was nice and hot. Then I get down there and start checking the 3 sensors with a voltmeter and it was fluctuating from about .2v to like .8v. It was doing it pretty steady and there was nothing weird so according to what I have read online these o2 sensors are in good working condition. So then I get back up and I noticed that the check engine light was off!!!! i turned the car off and then took it for a spin around the block and it's still off. What's going on here????

I had previously reset the computer and the same code came back twice. So how did it just come off??Any ideas??