P0420 & P0440 troublehooting help needed

[Nelsonmd]

So I had a P0141 last week, and I replaced the rear O2 sensor, after about 100 miles, I got another CEL. Had it checked tonight and I have P0440 and P0420. I have looked at the FSM, and the troubleshooting steps are quite extensive. Has anyone seen this before and know what the most likely cause is? I guess I am hoping there is a common minor issue that cant throw both these codes without me having to pony up for a new catalytic converter.

I know the P0420 is the catalytic converter, and the P0440 the evap system, but I find it odd that I didn't have these codes last week.

Anyone have any thoughts?

 

[Nelsonmd]

Ok, so no one has chimed in, so I will ask a follow up question.

I am going to inspect the Evap system for leaks first as that seems like a likely culprit for at least one of the codes due to all my rust.

Do any one know which fuel hoses I can replace with flex line or the like instead of OEM replacement? I am thinking I might need to replace the fuel filler pipe or the small tube next to it (what is the name of this, breather pipe?). Can I use a generic flex pipe or vacuum hose for these, or do I have to pay the exorbitant amount for OEM replacement?

If anyone has worked on their evap system, I would love any advice.

 

[GottaBeTRD]

hey man did you ever find out what the problem was?

 

[broncosi]

BUMP

any new info? I have the P0420 code after having new piping and flowmaster muffler installed from the cat back a few days ago?

 

[BrianSD_42]

Seems like pretty low miles for an OEM cat failure and O2 sensor failure.

He was at only 130k miles. I am at 213k wondering if i should replace my O2 sensor just because it is so old.

 

[Nelsonmd]

Hey guys, sorry I didn't see the bump on this. I have not solved the issues per-se.

The P0440 I did solve, turned out it was a rusted through fuel filler pipe (caused vacuum loss on the tank, basically same effect as a bad gas cap, which is the most common cause of this code). I replaced the pipe (see my build thread in my sig).

The P0420 I still have. I did find out that I have some exhaust leaks from a rusted out flange (between the 2 CAT's). I have partially welded it shut, but I still have the code (though it takes a long time to turn on) and I found that I still have a bit of a leak at that flange on the top, where I couldn't get the welder. I have some exhaust patch putty I am going to try to use to patch it and see once and for all if the P0420 is just being caused by an exhaust leak. If not, then I will be replacing both CAT's.

I already replaced the rear O2 sensor, so I know it's not that.

 

[broncosi]

Ok. I won't waste my time then because everyone I know keeps telling me to replace the rear o2

 

[Nelsonmd]

Ok. I won't waste my time then because everyone I know keeps telling me to replace the rear o2

It's not bad advice, it just wasn't my problem. Check for leaks first as that is free. Then replace the O2 sensor, then the CAT. That is the order of least to most expensive fixes, which is probably why that is the order Toyota suggests for troubleshooting.

 

[fenrisx]

That sounds about right.. I've had the P0420 for a few years now. I've also had my rear 02 get knocked/blown off during all of this.. and it wasn't that. The flange you're referring to on mine is also rusted pretty bad, but I haven't confirmed if it's leaking or not.

I recently had a Borla muffler welded up on mine, and they recommended chopping that flange off, and putting a new one in. That was an extra $50 I didn't have to spend at the time however.

I'll have to check that out soon.