P0420 2.7 l

I've got an issue on my 5 lugger. I'm setting p0420. Tried new o2s, replaced headers, stitched up crack in front of cat and I'm still setting the code. Anyone who dealt with the code figured something out?

I'm long long over due on smog.

 

Use an OBD II tool like Torque/adapter, maybe a scan gauge, to check your fuel trims. If they are plus or minus 10 or more check your fuel pressure. It could be you have low fuel pressure causing a lean condition. Which is exactly what caused my p0420 code.

My solution was a new fuel pump URD USA walbro255 kit.

 

Everything I read on this code points to a bad catalytic converter.

"Stitching" may not be enough. The internals of the CAT may simply be shot.

11 yr. old truck.

 

^this^ you need a new cat.

 

A fuel pump fixed a catalyst efficiency below threshold code? Sure you didn't have a P0171 or P0174 system too lean code?

 

It's definitely the cat, best way to confirm is graphing the o2/AF sensors while switching fuel trims. But really most tech's can smell it. If it smells like raw fuel after its warmed up the cat is shot, there is no cheap fix unfortunately.

Cat's can fail due to many causes, but not very often to they get better after a repair. Most cats fail due to wear in todays modern EFI engines.

 

Cats don't die or wear out, they are killed. The definition of a catalyst is something that causes a chemical reaction without undergoing any chemical change itself. If you just put in a new cat, chances are it will be dead soon too. There is something going on killing the cat.

 

Yes I'm positive. I fought this for a long time..

The cat probably isn't bad. Take my advice and check the fuel pressure. I lean condition can trigger the catalytic efficiency code. It's worth a try for as simple and cheap as it is.

 

Here are numbers to show what lead me to the fuel pump.
[SOLVED] P0420 lurching/hesitating/surging/searching - fuel pump

 

From what I gather from a quick skim of that thread, it seems to me that the extreme lean condition killed your cats, you replaced them, then replaced the fuel pump which was the root of your problem. No?

And according to your post #20 in that thread, your codes were P0171 and P0174 like I mentioned.

 

No my cats weren't bad. Replacing them only temporarily hid my issue. The codes came back. Replacing the fuel pump, and fixing the lean condition solved the problem.

The 1st and 2nd set of cats are both still good.

 

I already have done the urd fuel pump mod and put in a filter inline.

I'm reading only long term fuel trim, no short term at all. My up o2 won't read on my scanner but can be watched on a expensive scanner.

On cats, I'm thinking either getting one from rock auto(not ca legal tho) or getting universal ones from the first gens to weld in place of mine.

 

I've said my piece. Sounds like you've done some "custom" work. I'd still check fuel pressure because it's not hard. Idk what OBD tool you have but it doesn't sound like a good one. Good luck.

 

I had this problem for a long time. Most of the time it was P0420 and even got P0430 somtimes. And it can be my cats, i have no cats and an O2 sim.

When looking at my recorded fuel trims, they were moving a lot but were still inside the limit so you're not getting a code for a bad AFR sensor. Lately i find that the dealer has not reinstalled the gasket on the MAF sensor (AFE CAI) so there was a vacuum leak affecting the MAF sensor reading. Since i've installed a new gasket, codes are gone.

I would say look for vacuum leak on air intake components or leaks on exhaust line before O2 sensor.

 

Thank you, I'll give that a shot first and see what's up.

 

Yeah, I jumped on the urd pump. It's just a simple Bluetooth module. Thank you, I'll have to check that as well.

 

Check out the Torque app(android) you can check almost everything with it and a simple Bluetooth OBD reader.
Example from my truck when I was having the problem.

 

That's the same I'm running. My short term and upstream sensor ain't reading. On other vehicles it does read.

 

That sounds like a problem that could cause your issue..

 

What I was told was that bad cats will do that. Plus I get horrible mpg, for a for cylinder.