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Discussion Starter · #1 ·
A little background. Have owned a 2007 Sky base 2.4L with 25,000 miles for the last 3 years. Last Oct. before I put the Sky away for the winter the check engine light came on. Tried resetting it a couple of times but after a day or two it was back. Took it to the local GM dealer, they said it Coded P0420, and that test indicated a faulty cat. Over the winter I replaced both O2 sensors and the factory cat, which really didn't look bad, with a Magnflow #49226. Third outing this year and the check engine light is back on. I'm a little perplexed as to where to look next, anybody care to offer up some insight?

Thanks in advance
Chris
 

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How much have you driven it with the new cat? "Three outings could mean a lot of things. The manual advises that a new cat may set the code due to outgassing. It advises an hour at highway speeds.
 

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Discussion Starter · #4 ·
Thanks ,
Have about 2 hours driving time on the new cat, only about 5 minutes of that at 70-80 mph, the rest has been in city under 35 mph driving. I'll reset again and the next decent day we get I'll take it out and drive it like I stole it. God I'm gonna hate that 😁
 

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Discussion Starter · #5 ·
Have not tried the 02 extender, but might if I can't get this figured out. Have thought about a dummy 02 sensor as well, but not really the route I'd prefer to go.
 

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The MagnaFlow high flow cat will not scrub the exhaust as well as the stock cat. The way P0420 is set is the front O2 samples the air coming out of the engine. The exhaust then goes through the cat and the rear O2 samples that air. The two samples are compared and if the difference between the two is out of the ECMs acceptable range, the ECM believes the cat isn't doing it's job, thus malfunctioning and broken, and sets P0420.

Since the MagnaFlow cat flows better, the trade off is a less clean result that is out of the range of the ECM. An extender will move the rear O2 out of the optimal exhaust stream and cause it to read lower emission levels. High Flow cats don't always cause this problem so one person with the exact same cat won't have the issue but you will. A spacer would be better than a spoofer.
 

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Discussion Starter · #7 ·
Thanks for all the info guys. I spent an hour and fifteen minutes on the interstate this evening doing between 65-80. I'll reset the code tomorrow and see what happens. Will keep you posted.
 

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Thanks for all the info guys. I spent an hour and fifteen minutes on the interstate this evening doing between 65-80. I'll reset the code tomorrow and see what happens. Will keep you posted.
Put some cataclean in it first.
 

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A little background. Have owned a 2007 Sky base 2.4L with 25,000 miles for the last 3 years. Last Oct. before I put the Sky away for the winter the check engine light came on. Tried resetting it a couple of times but after a day or two it was back. Took it to the local GM dealer, they said it Coded P0420, and that test indicated a faulty cat. Over the winter I replaced both O2 sensors and the factory cat, which really didn't look bad, with a Magnflow #49226. Third outing this year and the check engine light is back on. I'm a little perplexed as to where to look next, anybody care to offer up some insight?

Thanks in advance
Chris
Hi Chris,
I have a 2007 Base also and recently the engine light came on. Took it to Chevy and it wasn't the engine but the Solenoids were the problem. Both replaced and all is well. Suggest you check them. Good luck.
Sumano
 
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