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P0420 code AFTER header install

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Mrjonjon

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Discussion starter · #1 ·
So after a few hours of searching previous posts, I still haven't found a problem similar to mine. I had the P0420 code and cleared it several times in about 6 months. I finally purchased and installed JBA shorty headers but used my factory cats which looked to be in great shape. I had the battery disconnected throughout the install process. Once finished, I reconnected the battery and drove the truck for over 100 miles. Then I went back and retorqued all of the header bolts. Well today the P0420 code came back. I also run a MBRP catback exhaust, no intake mods. My question is, could it be just bad o2 sensors, or do I really need a tune.

No other exhaust mods such as hf cats or aftermarket b pipes.

2005 Flex fuel SE crew cab

Thanks.
 
#2 · (Edited)
You should find out your A/F ratio to be sure you are not running rich. If that's okay, replace the sensor.

Did you ensure you had new gaskets installed, and not some cheap paper type gaskets?
 
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Discussion starter · #4 ·
Thanks for the quick replies. I'm really hoping its not a bad cat since it was a huge pia for this install. But just to clarify, I know uprev will definitely make the truck run better, but it is necessary/highly recommended? Basically, can I do any damage to the motor if I don't get it done right away?
 
Discussion starter · #7 ·
Right on. Thanks again. I'll check out my A/F and change out the gaskets ASAP. Hopefully the cats hold out. I was just thinkin that running the o2 sensors that long with cracked manifolds might have ruined them. But I'd rather start with small fixes before throwing a bunch of time into tearin the new headers back off.
 
#8 ·
If you didn't check the afrs post header install then you could likely be running rich and possible destroyed the OEM cats in that amount of time without being tuned. This is just a senerio to run by you and has happened quite a bit with guys not checking the afrs post headers. Hope its not the case and just a leaking gasket.
 
Discussion starter · #9 ·
So here's an update and any further help would be greatly appreciated cause I'm tearin what's left of my hair out! So I got new OEM manifold gaskets as suggested. When I took the exhaust apart, the front drivers cat was completely in pieces internally. So much so that all all of the pieces had made their way to the rear cat and clogged it. Got lucky that it didn't get sucked back into the motor. Anyway, so I cleaned out all of the pieces and decided to hollow out the passenger side as well. Basically I'm thinking its as close to a LT header as I can get without buyin another set.

So with the new Manifold gaskets, and new rear b-pipe gaskets I thought I was set. But after a day of driving, now I have both the p0420 and p0430. I realize that this is probably from hollowing the cats. So should I try defoulers? If so, would I put them in the front or rear o2 sensors? Or do I need a tune?

I'm also currently checking on a possible slight exhaust leak but I'm trying to basically nip this thing all in one shot.

Btw, I have JBA shorties, hollowed front cats, stock b pipes w stock cats and a MBRP exhaust.

Thanks
 
#10 ·
Yes you need a tune (PM'd). You also need to either hollow out the other stock B pipe, or better yet pick up a quality set of Cajun aftermarkets. By hollowing out one side and not the other you're really throwing the truck for a loop, ecu probably has no idea whats going on
 
#14 ·
You need catted bpipes and a uprev tune then you will be set. The stock bpipes will not work because the sensor is in front of the rear cats.
 
#15 ·
Uprev could just turn off the codes...


Sent from my Autoguide iPhone app
 
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#16 ·
Mrjonjon said:
Both b pipes are still intact. I only hollowed the front 2 cats. I have a 4x4 so I had 4 cats total.
Click to expand...
sorry misunderstood your post.. thought you hollowed out one side and left the other stock! lol
 
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seymore4
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