Service code P0420

[superfish]

Hey guys as you can tell iM new here and well we just got this 00' nsx, well I took it up to local auto zone here to get check engine light checked out and came up with this code Po420 which I beleive is the cat. converter. I was told it was this when I received the car and it was from the supercharger originally being wired incorrectly. Well all that is sorted out now is there any options I have insted of replacing the catconverter? I was told these cars have 4 is that true? One other ? I need to learn alot more about this car and have been surfing this site for info any other ideas would be great.
Thanks Dave

 

[Daedalus]

It may just be that you need new 02 sensors. Each cat has a sensor before the cat and a sensor after. The sensors before the cat are feedback sensors for fuel trim, to get the AF ratio in the sweet spot for performance and emissions. The 2nd sensor is purely to tell how well the cat is doing its job, by comparing readings to the primary O2. If one or both sensors are sluggish or bad, the computer may interpret it as the cat being bad. Don't know why you'd mess with it to install a SC though.
A tech should be able to make an educated guess based on watching O2 feedback on a scanner.
How many miles? What year? Have you had it smogged? Results?

 

[Larry Bastanza]

Every P0420 or P0430 code I have seen has required a new cat. If the system was running lean it will kill the cat is a heartbeat. Typically the 02 sensors have there own codes. To be sure you could swap the secondary(after the cat) 02 sensor from the rear bank to the front bank. If you get a 0430 then it could be the 02 sensor.

The P0420 (bank1,sensor2) is the rear cat BTW(Bank 1 is the rear). If you were getting an P0139 it would tell you the secondary 02 sensor is sluggush/slow response.

HTH,
LarryB

 

[heretic]

I have the same problem. First I replaced BOTH rear O2 sensors b\c one was bad. I hoped this would fix my MIL but it did not. Now the only thing left is the cat and my S\C was running rich for a while which is what I think killed the rear cat.