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Beating a dead horse p0420

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11K views 17 replies 6 participants last post by  mikejamesbyma  
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#1 · (Edited)
New guy here. :) Was looking for some quick info in regards to the P0420 issue. It's a family members car so I'll do the best I can to explain...

2006 2.5l Altima- 120k. Runs fine, no audible exh leaks and no stench. No exccesive oil consumption either.. Cel has been on for 3 weeks.

From what i've gathered it's defintely cat/manifold. My questions are...

1: Can it possibly be anything else? Would a bad 02 sensor or exhaust leak cause the code or would a different code pop up?

1.5: I'm a bit confused when it comes to clearing the code. Will a new one fix the issue? I assume yes but am confused when other members talk about header installs in the same thread as the oem replacement option.

2: I'm very worried about the cat material getting into the engine. What causes it? Prolonged driving with a bad cat or just a random occurrence?

3: Lots of options for replacement. I've been looking at them on ebay, these are the two in particular.

I can't post links but one is from "bestandfox" for $240 or one from "bearriverconverters" for $208

Leaning towards the one from bestandfox, though the other one has sold a bunch in comparison.

I need some help here guys. :confused:
 
#2 · (Edited)
The OEM precat is not well made and placed 2 close to the engine block. That causes the cat material to heat up the. Break apart and get sucked back on to the engine by the normal exhaust back pressure. Since the cat material is ceramics and platinum and other porous materials it damages the cinder walls and pistons and a lot of other nasty things. The first symptom is engine oil consumption, but can escalate rather quickly. There are.many horror stories of completely blow. Engines due to the the precat P
0420 is almost always a precat. The longer you wait the more damage it will do to the engine.
You can replace it with an oem type header with precat. The best and fox is ok. Catless header is the other way to go. Its also cheaper and gives the car a bit more power. If you have emissions inspections you will have to be careful. If you want to go the header root let us know. We can give you all the info on where to buy it and what you need. The OEM type replacement will run you some cash but since time is a factor you might not have a choice.

I personally have an xs header on my 06 2.5 I took the stock precat off at 80k. It was actually in great condition but I just dont want to worry .

Sent from my XT1060
 
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#11 · (Edited)
hey I need your help

Im buying an altima tomorrow after researching many cars. I understand this pre cat problem caused nightmares for others who didnt know about it .

where is the peice I need to fix it? do you have a DIRECT link for the parts I need?? can someone who knows about cars fix it? or is it something needed to be done by a tec?

I have a check engine light on the car im buying tomorrow, I would like to do the pre cat fix. Can I tell if damage has been done?
 
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#3 ·
You can also check RockAuto.com (with minimal googling you can always find a 5% off coupon code too). I went OEM replacement since I have emission tests and didn't want to deal with changing the header out yearly. Personally I went Dorman- cheapest of the options but also came with a warranty on the part. I've been happy with it so far (30k or so since change)- no complaints at all.
 
#4 ·
Once you get a P0420, the converter will have to be replaced to clear that code. The deterioration of the precat is generally the cause as Ed has pointed out. An 02 sensor will not clear a p0420.
 
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#5 ·
Ed, thank you for the explanation. Longer = More damage, got it. Iyho, is 3 weeks LONG in this particular situation?? I advised him to stop driving it but havent heard back yet. He does have a new car so I don't see why he would after that warning.

A header is not an option here in Illinois. Even if it were I don't think he'd go for it. :)

Amp, I was considering the Dorman from RA as well, but seeing as how he might just sell it after the repair it comes down to getting it good to go for the least amount possible without buying junk. Iirc it came to 291.xx shipped with the code. Not bad but still $50/$80 more than cheapies.

Mike, ty.
 
#14 ·
You should have that code checked ASAP.

The precat is part of your manifold. if you're not sure where the manifold is, then you'll need to have the part taken care of by a mechanic.

Maybe Ed can post up a link to Mark's email. He'll hook you up with all you need.
 
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#17 ·
Ended up buying the bestandfox convertor off ebay. :) Replaced it today and so far so good. Good fitment and came with everything for the install. Did have to use fire on the lower bolts but the o2 came out easier than I thought it would. The oil was where it should be and it appears the motor was not damaged.

I must ask, is it common for the driver and passenger side floorboards to rust out on this gen? Also, what would cause a clunking in the rear over bumps? Shocks mounts, anything common? Just a few things I noticed while looking/inspecting his car. :)
 
#18 ·
Yes, extremely common for the floorboards to rot out. Happens to just about all of them in salt areas.

Clunking in the rear is most commonly the rear sway bar bushings.


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