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I have two codes both tied to the O2 sensors. Do not have the numbers at hand but will get. I have a cheap code reader. Is it pretty cut and dried if you use a quality reader and the O2 sensors show out of spec? Also what are the odds two go at once? I have also seen there are some CAT issues. Mine has the 4 cyl. Seems to run fine at 98,000 miles.
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Codes are PO421 and PO431. Two errors for each code.
I am not super knowledgeable, please take everything with a grain of salt. I am very new to cars, but I have been looking into this issue for a while.
I have a 166k mile Spyder GS with the same codes.

PO421 and PO431 are the catalytic converter warmup codes. They seem to be a common problem on these cars. The codes are only referencing the two cat / header combo units in the engine bay, the large "main" cat under the car has no sensors and does not affect the computer in any way.

There is some information on this forum about these codes and potentially using o2 sensor spacers to fix the false positive check engine light. It looks like some dealers were doing a ECU re-flash to fix the issue when the car was still under warranty. This leads me to believe there is some kind of software bug with the ECU that causes the false positive reading.

Or, you know, one of the 4 o2 sensors or one of the two cats are worn out and need to be replaced. You should also make sure all of the o2 sensors are plugged in haha.
Let me know if you fix it, I have still not tried the sensor replacement / spacers. I have just been driving it with the engine light and pulling the codes every once and a while to make sure nothing new has come up.

EDIT: Thank you Sabertooth for telling me I was wrong! Please read his reply. Dealers were also replacing the cats with the re-flash. Spacers only hide the engine light. Looks like fix is probably either sensors or a cats. There is info on which one you need / where in this thread, including a PDF with what all the codes mean.
 

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2009 GS Turbo. 2007 Mid Engine GT
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I am not super knowledgeable, please take everything with a grain of salt. I am very new to cars, but I have been looking into this issue for a while.
I have a 166k mile Spyder GS with the same codes.

PO421 and PO431 are the catalytic converter warmup codes. They seem to be a common problem on these cars. The codes are only referencing the two cat / header combo units in the engine bay, the large "main" cat under the car has no sensors and does not affect the computer in any way.

There is some information on this forum about these codes and potentially using o2 sensor spacers to fix the false positive. It looks like some dealers were doing a ECU re-flash to fix the issue when the car was still under warranty. This leads me to believe there is some kind of software bug with the ECU that causes the false positive reading.

Or, you know, one of the 4 o2 sensors or one of the two cats are worn out and need to be replaced. You should also make sure all of the o2 sensors are plugged in haha.
Let me know if you fix it, I have still not tried the sensor replacement / spacers. I have just been driving it with the engine light and pulling the codes every once and a while to make sure nothing new has come up.
The factory recall was actually a change in the fueling maps so that it wasn't so rich. They pulled it down about 0.2-0.4 AFR across most of the fuel map. Less fuel, less prone to clogging. If the engine ran hotter, the extra fuel likely would have kept the cats hotter. Not in this case.

So it wasn't a false positive, and the dealer also replaced the cats on the cars that had already thrown the code.

O2 spacers fix nothing. They just hide the check engine light as the problem grows. The clogged cats eat up your power, hurting fuel economy significantly as they do it. It would be like if I tuned someone's cats out but they were still busted. Nothing would get better. Or putting a bandaid on a broken leg then going for a run. It fixes nothing, and just lets the problem get worse
 
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