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Discussion Starter #1
SO my 2007 baselne sky has been throwing a bunch of codes for the past few months. Most have been for Catalytic converter issues. I have already changed out the downstream o2 sensor which actually did turn out to be faulty. I have also done a pressure test and found that I am not leaking pressure anywhere in the hoses. Checked the back pressure on the front side of the cat itself and there doesnt seem to be any building so the cat is not clogged. But im getting error code P0420 so my last option is to change out the upstream sensor now, which based on the diagnostic readings it is fluctuating more than it should. Does anyone know the OEM part number for an o7 sky for the bank 1 sensor 1?
 

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Not off hand but it is a pretty standard Narrow Band O2 sensor. You can go to your local auto parts store and have them look up the part. If you get a Bosch unit, you're as good as OEM. That's what I have in my 2.4.

Now, a cat can still flow but still be bad. A P0420 code is usually a bad downstream sensor but if you changed that, cleared the code, and it came back...it may be the cat. The 2007 2.4 cats got an extended warranty on them because they had problems with them. Unfortunately that was only good for 10 years.
 

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thanks for the notice, my sky is at 105,000 miles with a magnaflow 16664 cat back. I will check the oscillation readings on the bank 1 sensor 1. they can fluctuate but i believe they are supposed to be between .7v and 1.0v correct?
 

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this is what I found for an OEM sensor GM Part No: 12596701 12596701 - Genuine GM Sensor Asm-Heated Oxygen (Position 1) I think I might try replacing this first since a new magnaflow cat would be far more expensive.
The other thing is the new MagnaFlow cat may not solve the issue. There is another person on here (or the FB group...so hard to keep track of all the conversations sometimes) that has the P0420 code with a new MagnaFlow cat that is supposed to be a stock replacement, not a high flow, and he has changed both O2s. The general consensus is that the cat is flowing better than stock and thus throwing the code.

As for diagnosing the sensor itself, I have no idea what the range should be on that. @JohnWR would know more about those electronic things. LOL
 

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@Robotech....that'd be me (she). I ordered another cat directly from mag since the amazon guy abruptly refunded and didnt want to warranty the cat I had, so I'd assume it was defective. Come Monday we'll see. I toke my car to a GM dealership and they said live data showed the cat was at fault ?
 

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@Robotech....that'd be me (she). I ordered another cat directly from mag since the amazon guy abruptly refunded and didnt want to warranty the cat I had, so I'd assume it was defective. Come Monday we'll see. I toke my car to a GM dealership and they said live data showed the cat was at fault ?
My apologies for the pronoun screwup. Keep us in the loop as to what is going on with that. I'm interested in seeing how it works with the new cat from MagnaFlow...
 

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Just to throw my $0.02 in here. Are you a Redline???? 2.4L are notorious for going bad around the 90k mark, Redlines not so much... It doesn't matter what year, or what vehicle....anything with a 2.4L usually has the issue around that mark. I've known quite a few people...Malibu, Terrain, G6....all of them do it. It's as common as our WP issue. I thought I was having a cat issue. I have a turbo car and the readings on both were all jacked up.... So I ordered new O2 sensors and replaced both. Readings were still inconsistent. Turns out, the tuner that tuned my car for me, shut off the P0420 and the rear downstream sensor. Most here also don't know that the rear downstream does more then just tell you if your cat is working. It also adjusts fuel...although minuscule...it does adjust the fuel trims a bit and colaborates with the upstream to do so. So...that explained why my upstream was all over the place and why my car has gone to a much richer condition then when it was first tuned.
 

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I am interested to see what happens with the new cat as well.. there are some cats ive found from magnaflow that are significantly less costly though they are cut and weld ons instead of just bolt ons. what is the difference in HM grade and OEM grade? 2007 Saturn Sky Catalytic Converters | MagnaFlow
Magnaflow's documentation is pretty confusing, but it appears to me that the HM Grade have a smaller quantity of the catalyst, so they won't last as long as the OEM Grade. Hence the lower price.
 

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thanks for the notice, my sky is at 105,000 miles with a magnaflow 16664 cat back. I will check the oscillation readings on the bank 1 sensor 1. they can fluctuate but i believe they are supposed to be between .7v and 1.0v correct?
The output of a narrow-band O2 sensor should vary constantly between 0.1 and 0.9 V, with 0.9 indicating rich and 0.1 indicating lean.
 

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Mine is a 2009 2.4l at 105k miles. On my obd it says the 420 is in open loop (rich fuel to warm up the car). Like you stated @The_Ghost itll run rich when I drive.

I have a theory something isn't turning open loop off when I drive, so my downstream notices excessive fuel, and says hey the cat isn't working.
I keep thinking other factors, but then it'd show another code. Low coolant temp would throw a code, fuel injectors would throw a code...cars man....
 

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Discussion Starter #14
Just to throw my $0.02 in here. Are you a Redline???? 2.4L are notorious for going bad around the 90k mark, Redlines not so much... It doesn't matter what year, or what vehicle....anything with a 2.4L usually has the issue around that mark. I've known quite a few people...Malibu, Terrain, G6....all of them do it. It's as common as our WP issue. I thought I was having a cat issue. I have a turbo car and the readings on both were all jacked up.... So I ordered new O2 sensors and replaced both. Readings were still inconsistent. Turns out, the tuner that tuned my car for me, shut off the P0420 and the rear downstream sensor. Most here also don't know that the rear downstream does more then just tell you if your cat is working. It also adjusts fuel...although minuscule...it does adjust the fuel trims a bit and colaborates with the upstream to do so. So...that explained why my upstream was all over the place and why my car has gone to a much richer condition then when it was first tuned.
that makes sense but I have a base 2.4 at 105,000miles. I know the downstream is working because i changed it and retested it and it was reading constant on the diagnostic
 

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Discussion Starter #15
Magnaflow's documentation is pretty confusing, but it appears to me that the HM Grade have a smaller quantity of the catalyst, so they won't last as long as the OEM Grade. Hence the lower price.
do you have any experience of the aftermarket(magnaflow) cats throwing codes because they are technically not GM OEM parts?
 

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Never heard of the rear O2 playing a role in fueling. Not sure on the E67 logic but with our Grand Prixs (a little more primitive ECM) I know they were for cat operation verification only. This is the first I've heard they do more than just Cat calibration.
 

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Good news, my downstream o2 v was definitely lower in the .6 instead of high .7 and .8. The smog test approved of everything but the evaporative test which takes a few drives.
Life lesson, don't buy parts from Amazon even if it's a steal.
Total price for both 02 and cat : $568

It's not expensive to replace the cat compared to other cars, but if your oem cat looked clogged like mine. Go for it, plus you get a spec miata BbBRrRr!

Below is side by side with amazon taken out
 

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Discussion Starter #20
So i went ahead and bought a new upstream 02 sensor, cause thats cheaper to try replacing than the cat itself first. but then after I bought the sencor the engine check light disappeared. the ECM cleared the code on its own. I'm not confident that the problem is solved but if it comes back on again ill install the new sensor.
 
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