P0420 Cat?

**KennethJohnson** · 01-02-2016

After going through a series of checks I noticed my cat's going out.
My car threw a P0420 code after i replaced my Upstream O2 due to it throwing a previous code saying the Upstream 02 Sensor was bad.
Gave my cat a little tap, and there's a bit O' shaky noise.

Can anyone refer me to a cat with pipes bolt on I can buy that would need no adjustments or tinkering? I can't weld.

I was looking at a few on RockAuto and it said it wasn't legal for CA use. (I'm in California lol)

Also, when replacing a cat, would you have to re-tune your car?
(Might be a noob question sorry)

**KennethJohnson** · 01-02-2016

I just noticed the non CA legal ones are like half the price.

Can anyone explain?

**Reptile** · 01-02-2016

California...no more explanation necessary. LOL

Some aftermarket ones are a so called "high flow", and they don't really work as good as a quality converter. You usually get what you pay for on these things.

**KennethJohnson** · 01-03-2016

Originally Posted by Reptile

California...no more explanation necessary. LOL.

Haha damn. Would it be a good idea to strip one from a car lot?
I don't need a brand new one. Just one that won't throw codes.

And honestly I don't have to smog my car for another year and a half I just did. So this can easily be a project for later

**Scottydoggs** · 01-03-2016

take a down pipe with cat off a junk yard car, or cut it out and weld it in your car.

**robinsone** · 01-03-2016

The exact same thing just happened to me. Its too much coincidence that after replacing the upstream O2 sensor that I get a cat code. I believe the cat code is tripped when there is a difference in readings from upstream and downstream O2 sensors. I'm testing the theory as I've bought a downstream O2 sensor for all of $25 shipped. Both O2 sensors will be AC Delco, so I am quite interested to see if the CEL goes out after installing 2 new sensors to see what happens.

**SgtMarshal** · 01-03-2016

I have a catalytic converter sitting in my garage that I would sell for 40 bucks plus shipping. It is a factory unit with about 130,000 miles on it. I took it off when I installed a set of SD headers. should work fine, and still has exhaust pipe on each side.

**KennethJohnson** · 01-04-2016

I also got an upstream Delco O2 sensor.
Mind following up with me after you replace the Downstream sensor and put some miles on?

I was using my OBD2 and the downstream 02 sensor voltage was jumping around rapidly from what I understand that means a bad cat? Or maybe another bad sensor? :P
I might just get another downstream O2 also. But I swear I can hear a rattle in my Cat.

**robinsone** · 01-04-2016

Can do

**Bronco Boy** · 01-04-2016

Originally Posted by KennethJohnson

Can anyone refer me to a cat with pipes bolt on I can buy that would need no adjustments or tinkering? I can't weld.

Not sure on the CA aspect, but we have (did have) similar nazi-like rules here. I used a Walker #54627.

Here is my cat install: http://chrisb.users.superford.org/Gr...Converter.html

**KennethJohnson** · 01-06-2016

What other car years can I look for a cat on?
Am I limited to N/A 3.8L cars?

**Scottydoggs** · 01-06-2016

na or sc, the same. any w body cat should work fine.

**robinsone** · 01-13-2016

I pulled the negative battery cable just to see if that would solve the problem and it did. I have yet to swap out the rear 02 sensor, but I figured I might as well since I have the part, with 206k miles I'm going to go ahead and replace it. But as for the Cat 0420 code its disappeared.