alittle help thanks

Hey new to the forum,I have a 2002 Toyota Tacoma and everything runs great no problems but the check engine light is on. Code reads p0420 bank one, mechanic told me it was the catalytic converter so I ended up replacing it with the O2 sensor and light came back on. Initially it Came on after I put a new Flowmaster exhaust on. I noticed that the rear O2 sensor doesn't have a gasket , not sure if it had one or they forgot to put it on could this caused the problem even tho it says bank one? Any ideas would help thanks a lot

 

@mechanicjon

Also change your thread title to specifically address your problem - the h-e-l-p word is supposed to be used for people who need physical help / tow etc. plus it helps later for people searching for info w/ a similar issue!

 

A P0420 can be caused by a few different things, but if it really does run properly, and the O2 has been ruled out by replacement, it may very well be your cat. Is the flowmaster just cat back?

 

After seeing the title, I was tempted to start a "How to Create Meaningful Thread Titles That Attract Readers" thread.

 

Before or after the detailed explanation of the search feature? Sorry OP don't mean to bust you balls but theres alot of info on that code. 10 pages of threads listed. An exhaust leak can cause the code.
Do you have a code reader yourself? Being able to monitor ECU OBDII data is a big help.

 

My bad still new to this, Should of titled p0420 wtf could it be. I replaced my cat and 02 sensor bank one. I have a cat back flow master exhaust. Will have to get a code reader all the info will help thanks.

 

Is there any exhaust leaks? You need to put a gasket on the o2 sensor. What brand of o2 sensor? Also engine information v6 or 4cyl? California emissions or not? Do you have any kind of service manual or just what you can find on the internet? The o2 sensor behind the cat you replaced or in front?

 

Thanks for the reply. V6,cali ,replaced the bank one o2 sensor. The thing I noticed was when I got the exhaust done they didn't put on the rear o2 sensor gasket could that cause the check engine light to come on even tho it says p0420 bank one?

 

I don't want to sound like I'm being a jerk OP. I spend a good amount of my time helping people on TW. You answered some of my questions above, but not all. I didn't ask those questions for no reason. I'll be glad to help but it will take communication in detail.