Continued O2 sensor troubles

[Davy-Crockettm28]

A few months ago I started intermittently getting the CEL code p-0133. So I got a replacement sensor from NTK and tried replacing it. I had zero luck since it was seized so I sent my jeep and the NTK sensor over to my mechanic who was able to put it in for me. Cleared my check engine light for about a week, and now it has returned. Same P0133 code. I am genuinely at a lose of what to do next other than try a second new sensor. Any advice of further steps would be greatly appreciated!

 

[Davy-Crockettm28]

Tighten the bolts that hold the catalytic converters to the exhaust manifold.

I just had this happen the weekend out wheeling. Got a P0153 code. These bolts were loose….tightened all four and the CEL cleared after driving for about 25 miles.

I assume you mean the flange bolts around the Pre cats?

 

[Bigfoot-NM]

Yes….worth a try before spending money.

 

[Davy-Crockettm28]

Yes….worth a try before spending money.

Ill give it a try, thanks!

 

[Jerry Bransford]

A bad pre-catalytic converter can also be the root cause of erroneous O2 sensor CELs. I had those until one of my pre-cats failed catastrophically nearly completely blocking the main catalytic converter downstream. Replacing all three of my cats cured my O2 sensor error codes. The original O2 sensors were reinstalled into the new replacement cat system. Everything is still good 10+ years later.

 

[Ticks]

Exaust Manifold leaks.

 

[Davy-Crockettm28]

A bad pre-catalytic converter can also be the root cause of erroneous O2 sensor CELs. I had those until one of my pre-cats failed catastrophically nearly completely blocking the main catalytic converter downstream. Replacing all three of my cats cured my O2 sensor error codes. The original O2 sensors were reinstalled into the new replacement cat system. Everything is still good 10+ years later.

How can I tell if my pre-cats are going bad? I haven't noticed any signs of a bad catalytic converter, and I assume the pre cats would have similar symptoms to the main cat failing.

 

[Jerry Bransford]

How can I tell if my pre-cats are going bad? I haven't noticed any signs of a bad catalytic converter, and I assume the pre cats would have similar symptoms to the main cat failing.

Hard to say other than when replacing the O2 sensor with the correct NTK didn't cure the problem as happened to both you and I I'd be thinking it's likely the pre-cat that is fooling the PCM.

 

[Davy-Crockettm28]

Ok, ill keep that in mind. Hope its not, but I guess its the luck of the draw. If I do wind up needing to replace them are the magna flow Pre cats any good?

 

[Irun]

How can I tell if my pre-cats are going bad? I haven't noticed any signs of a bad catalytic converter, and I assume the pre cats would have similar symptoms to the main cat failing.

Drop the exhaust from the manifold and take a look inside the primary cats.

 

[Jerry Bransford]

Drop the exhaust from the manifold and take a look inside the primary cats.

Since when can the condition of a catalytic converter be known by just looking at its interior? They don't often come apart inside as mine did upon failure.

 

[Irun]

Since when can the condition of a catalytic converter be known by just looking at its interior? They don't often come apart inside as mine did upon failure.

I've seen them both come apart and be plugged. Sometimes it can be seen looking down into the primary cats and sometimes it can't.

 

[Davy-Crockettm28]

Hard to say other than when replacing the O2 sensor with the correct NTK didn't cure the problem as happened to both you and I I'd be thinking it's likely the pre-cat that is fooling the PCM.

One more question, in my research I haven't seen anything mentioning this but Id like to make sure, will precats made to fit a SWB work on an Unlimted?

 

[Jerry Bransford]

One more question, in my research I haven't seen anything mentioning this but Id like to make sure, will precats made to fit a SWB work on an Unlimited?

They are the same though Mopar doesn't sell the pre-cats separately, they are only sold as an assembly as shown below. But aftermarket providers do so you're good to go if you found some for the Unlimited. At least they are the same for your '05, did you find them from an Unlimited with a different model year? If so I can verify that after you give me the donor Unlimited's model year.

 

[Davy-Crockettm28]

They are the same though Mopar doesn't sell the pre-cats separately, they are only sold as an assembly as shown below. But aftermarket providers do so you're good to go if you found some for the Unlimited. At least they are the same for your '05, did you find them from an Unlimited with a different model year? If so I can verify that after you give me the donor Unlimited's model year.

View attachment 407743

I'm planning on buying one of direct fit kits ( looking at the Walker, AFE, or flowmaster kits ). They all have versions that work on 04-06.

also in the diagram you posted, what is the #2 pointing to on the back half of the down pipe? It looks like that's the main CAT but the flange after it is throwing me off.

Edited to add: This is the AFE kit i'm looking at https://www.extremeterrain.com/afe-...qhoCdUwQAvD_BwE&gclsrc=aw.ds#customer_reviews

 

[Jerry Bransford]

also in the diagram you posted, what is the #2 pointing to on the back half of the down pipe? It looks like that's the main CAT but the flange after it is throwing me off.

That's the main catalytic converter. The flange is there so the tailpipe and muffler can bolt up to it.

 

[Davy-Crockettm28]

That's the main catalytic converter. The flange is there so the rest of the tailpipe and muffler can bolt up to it.

That's what I thought.

I've seen good things on here about the walker replacement kits, do you have any experience with them?

 

[Jerry Bransford]

That's what I thought.

I've seen good things on here about the walker replacement kits, do you have any experience with them?

No but like Magnaflow they seem to have a good reputation.

 

[Davy-Crockettm28]

No but like Magnaflow they seem to have a good reputation

Ok cool, thank you for all help.

 

[Indy05Rubi]

Not sure what your timeline is for going down this path, but I literally just click "purchase" on an entire Walker setup from the precats all the way back through the muffler. Going to have a local shop do the install in a couple weeks and am happy to share my experience once we get it all bolted up.