Converters are going. Tuner to shut off CEL from aftermarket cats? - JeepForum.com
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post #1 of 10 Old 05-18-2020, 01:14 PM Thread Starter
Th0r
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Converters are going. Tuner to shut off CEL from aftermarket cats?

At 170k my converters are tossing codes on longer trips. Also explains the crappier than usual fuel mileage. I'm weighing the options of high-flows, aftermarket, or even just gutting. Either one, from my experience, is likely to toss a CEL light anyway when going away from factory. Do any of the tuners on the market offer an option to modify post cat readings? My Jeep is a 2009 4.7L.

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post #2 of 10 Old 05-18-2020, 01:33 PM
90grandoneer
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I doubt you'll find any legit. place that'll do that for you, as it is tampering with the emission systems on the vehicle which could result in huge fines for the tuner. Years ago, Diablosport would allow you to shut off the EGR system, but as soon as the word was out they had to remove it from their tuners for this reason.

The only way I know of is to purchase an HP Tuner and modify your post cat. readings at your own risk. All this being said, you should be able to find some (approved) aftermarket cats. that'll work fine without going through all this. I've had JBA high flow cats. on my 5.7 Hemi LX for over a dozen years and have never had any problems of any sort.....codes or passing emissions tests.

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post #3 of 10 Old 05-18-2020, 01:57 PM
jtec
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If the state doing the emissions testing quizzes the PCM as to its current program the new (modified) may not be recognized.

What are the codes and why not fix the issue?
the fact that they only code on long trips would have me asking WHY - its often the short trips with cold cats that are problematic.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #4 of 10 Old 05-19-2020, 07:01 AM
50Junkie
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Keep in mind, cats don't fail on their own or wear out. You need to figure out what is damaging them. Where are your fuel trims? Losing oil or coolant? All it takes is a pinhole upstream or downstream of a cat to affect o2 sensor readings, which will make the pcm change fuel trims when it doesn't need to. Misfires?

If you can get live data out, check upstream and downstream o2 readings. Upstream should switch between rich and lean. Rear o2 should be relatively steady and above .6V. Are you getting P0420/0430 codes?
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post #5 of 10 Old 05-19-2020, 08:53 AM Thread Starter
Th0r
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No emissions to worry about. I'd prefer to put cats back on, but I don't want to spend a ton on OEM. I see lots of cars come into out shop with a/m cats and post cat CELs, and I had the same issue when I put high-flows on the 5.7 300C, so that's why I was looking at the tuner route.

P0420 only. All rubber feeding the intake is in good shape and can't find a leak when spraying with intake cleaner. No coolant loss. Oil stays in the "full" range of the dipstick between 5k mile oil changes so it make use 1/2 qt or so. Readings on 02's have been ok every time we've checked. No audible exhaust leaks. The cat does rattle.
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post #6 of 10 Old 05-19-2020, 09:14 AM
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Quote:
Originally Posted by Th0r View Post
... crappier than usual fuel mileage...
that's money going out your tailpipe.

when it was me, i just bit the bullet to fix and pay once. otherwise you're paying for it every fill up in lost mileage.

i went with magnaflow stainless cats and a set of mopar O2 sensors to fix my own p420 issues (Y pipe rusted out). unfortunately the jeep hasn't moved and they've been sitting in the garage for a couple months because i haven't had time with this whole pandemic (it was pretty bad here in NJ), but soon!

'05 WK Limited 5.7 Hemi
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post #7 of 10 Old 05-19-2020, 12:17 PM
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I gutted mine because PO had leaking manifolds that killed it. I just clear the codes every few days, pretty annoying but not quite $700 magnaflow annoying.

I don't think it actually affects the trims much, they're controlled by upstream O2s. Getting bad downstream will just give you the P0420 (or P0430). Lmk if this is not accurate.

My millage goes down to ≈12l/100kms on highway which I think is pretty close to original..

I keep trying local wreckers and will prob put one in if I can find at a reasonable price..

05 WK Limited 5.7, QDII, OME HD, 265/70/17 1.25" Spydertrax, CC, MBRP SS, 250xxxkms
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post #8 of 10 Old 05-19-2020, 09:32 PM
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I replaced mine with resonators. Current tuners don’t allow for you to disable the associated codes anymore. I messed around with o2 spacers for a bit including stuffing with varying amount of steel wool with limited success. In the end, I got a custom tune to get rid of the codes. Runs great but the exhaust smell is rather noxious. It’s probably not a permanent fix for me, but my own cats had almost 200k miles and I wasn’t prepared to buy new for it.

I may either weld in aftermarkets at some point, or spring for the magnaflow setup. It’s currently a bit over $700 on amazon for the non federal emission version. At one point it was down to the mid $400 range. Bosal has what appears to be a magnaflow clone for just under $500 on rockauto too.
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post #9 of 10 Old 05-20-2020, 05:47 AM
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Raffish you might want to look at o2 sensor inputs as the front AND rear often determine fuel trims*, also with your cat codes WHAT is if any 'actiontaken' by PCM ?

A little anal but for the record - removing or rendering inop an emission device is ILLEGAL that is a federal regulation, does not matter what state..

* old days it was only precat for trims.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #10 of 10 Old 05-20-2020, 06:52 AM
50Junkie
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A quick check showed Walker direct fit for $400ish for 4.7 and $300ish for 3.7. Not sure which engine you have. No listing from them for a 5.7.
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