Engine code P0431

[KCsTJ]

On day 3 of my new to me 05 Sport with 101k I'm in rush hour traffic, the tj bucks 1x and the CEL comes on.

AZ reads the CEL and it shows a P-0431 code which says...
"Warm Up Catalyst Efficiency Below Threshold (Bank 2)"

There are two catalytic converters coming off the exhaust manifold.
My question is probably obvious but it's my first 4.0 and I guess I just need some confirmation before I she'll out $600 plus labor.

If 1 cat throws a code 0431 should I go ahead and replace both at the same time?
Looks like a cat is $300 or so. I can't weld.
Should I bite the bullet and replace both Bank 2 and Bank 1 at he same time for PM purposes ?

 

[Vcook]

Just an idea, no experience of my own with this: https://www.amazon.com/dp/B01MUT0383/?tag=wranglerorg-20

 

[Fletcher34]

A code P0431 may mean that one or more of the following has probably happened:

The catalytic converter is no longer functioning properly
An oxygen sensor is not reading (functioning) properly
There is an exhaust leak

I'd take it to a shop that can read live data while driving it. If they tell you it's an o2 sensor (I think this is your most likely culprit), I'd replace all 4 honestly. Get the NTK/NGK sensors and get them on Amazon. I got all 4 for about $120 which will be much much much cheaper than the dealership will charge. Do not let them use aftermarket sensors.

 

[Jerry Bransford]

I'd bet on one of the precats being bad, as is what caused my O2 sensor check engine light codes. Those pre-cats come in pairs, that's what I'd install and reuse your existing O2 sensors. I was getting lots of check engine lights and codes and replacing the cats with reusing the existing O2 sensors cured them.

 

[KCsTJ]

Thank you @Vcook, @Fletcher34 and @Jerry Bransford .
All good info.
I should be able to sort things out from here.

 

[KCsTJ]

I think I have this figured out.
At closing the dealer gave me a shop invoice for a coil rail and 2 02 sensors installed 800 miles ago (plus a new coil rail).
Because repair shops typically buy the cheapest parts for widest profit margin I'm speculating that the wrong 02 sensors were installed.
Since I can't identify the existing 02 sensors I'll just replace bank 1 and bank 2 with the correct new NTK 02 sensors and report back.
Next purchase has to be a good diagnostic reader. :/

 

[Fletcher34]

I think I have this figured out.
At closing the dealer gave me a shop invoice for a coil rail and 2 02 sensors installed 800 miles ago (plus a new coil rail).
Because repair shops typically buy the cheapest parts for widest profit margin I'm speculating that the wrong 02 sensors were installed.
Since I can't identify the existing 02 sensors I'll just replace bank 1 and bank 2 with the correct new NTK 02 sensors and report back.
Next purchase has to be a good diagnostic reader. :/

If they used anything other than NTK..... that's a problem.

 

[KCsTJ]

If they used anything other than NTK..... that's a problem.

That's what I'm banking on.
If the repair shop doesn't have '4 x 4' or 'Jeep' in its name they probably won't know Jeeps and therefore won't know the right parts to use.

 

[KCsTJ]

And to be clear, can someone confirm on a 4.0 l6:

Bank 1 02 sensor serves cyls 1,2 and 3.
Bank 2 02 sensor serves cyls 4,5 and 6.

Is this correct ?

 

[KCsTJ]

Just an idea, no experience of my own with this: https://www.amazon.com/dp/B01MUT0383/?tag=wranglerorg-20

That looks like it bolts on, might need a weld or 2.
Thanks I need to do more research as usual... :/
And if I do the install, what might I do PM wise, e.g. tighten or retorque all manifold bolts, etc... ? While im on that side of a new 2 me 4.0 with 101k miles?

 

[twistedlv]

That looks like it bolts on, might need a weld or 2.
Thanks I need to do more research as usual... :/
And if I do the install, what might I do PM wise, e.g. tighten or retorque all manifold bolts, etc... ? While im on that side of a new 2 me 4.0 with 101k miles?

Does your rear main seal leak? Perfect time to address that while the pipe is off.

 

[Boinked]

Does your rear main seal leak? Perfect time to address that while the pipe is off.

Thats always a fun job (sarcasm) but i agree

 

[KCsTJ]

Does your rear main seal leak? Perfect time to address that while the pipe is off.

So far as I can tell, no RMS leak at all. You're right this would be a good time but I'm good there!

 

[AndyG]

So far as I can tell, no RMS leak at all. You're right this would be a good time but I'm good there!

How did this work out sir? My 06 has a 431code .

 

[KCsTJ]

How did this work out sir? My 06 has a 431code .

I ended up having to replace the precats. I bought the Evan Fisher precats. That took care of the engines codes and the poor engine performance.
Think I paid around $260

 

[AndyG]

Cool,I think I'm ok , loose pre cats may be my issue.. I replaced the sensor , the code came back

The Jeep runs awesome

Noticed I could move the pipe .. thinking thats the cause.

 

[LONGJP2]

I ended up having to replace the precats. I bought the Evan Fisher precats. That took care of the engines codes and the poor engine performance.
Think I paid around $260

Were you happy with the fitment?

 

[KCsTJ]

Yes, the fitment was fine. However the Evan Fisher has developed an annoying intermittent rattle that comes and goes, something came loose I think inside the pipes.
Haven't had time to look at this yet

 

[Huckleberry]

My 2005 Wrangler has a P0431 code
And I can’t get it to reset
Jeep runs great
Can I run Jeep without worrying about that pesky code?

 

[Mongo61]

Just an idea, no experience of my own with this: https://www.amazon.com/dp/B01MUT0383/?tag=wranglerorg-20

Thank you