P0139 during hot weather
 

Well I cannot stand it anymore. Last year I kept getting the check engine light for 1-3 days then it would go off. I went to Autozone and got code P0139, I almost bought a new O2 sensor but decided that it was extremely weird that it would reset by itself. Then, called Mazda to check for any recalls and turns out that there was a new reprogramming due for my VIN #. It was around fall, then suddenly the code went away, no more check engine! I did some research and someone said that when the weather got hot, some RX-8s would get the P0139, that it was nothing. It was winter so the code didn't come up for 3-4 months. 2 weeks ago, when cold weather finally left South FL (in april??? global warming anyone :) ), boom! there was my check engine light on again, then it would go off by itself. The cycle has started anew.:banghead:

I'm stuck, I googled the web for anything specific re: the code, temperature and the RX-8 but nothing. What should I do????? Mine is a 2004 RX-8, 60K miles, just did the 60K servicing. Any help will be greatly appreciated!

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Are you running with a cat or mid-pipe?
Have you checked for exhaust leaks?
Can you turn the O2 sensor by hand (this would mean it was loose)?
I think with this code people would get their cat replaced under warranty or go with a mid-pipe.
I haven't read anything otherwise to say that it could be one of the other systems mentioned in the attached shop manual (but not saying it couldn't).

Sorry couldn't be much help, too many variables with uncertainty.

you have a bad cat or a bad o2 sensor

Thanks Jon316G and zoom44. I will check first if the rear O2 sensor is loose to see if that might be it. If not then I'll have to see if someone can check my cat. FL doesn't check emissions, AFAIK, but I want to keep the car as close to factory as possible as I'm not that hardcore into racing. Is there anyway I can check if it's the rear O2 sensor or cat myself without going to the dealer? My closest dealer was supposed to do an oil change and gave the car back to me without doing it and charged me, but I noticed and my usual service rep took care of me. Don't know, are dealers mandated by Federal law to check catalytic converters since they reduce emissions???


Last, I tried googling for an image of the rear O2 sensor and couldn't find it. Where exactly is it?


Thanks again.

Update: got the OEM sensor and changed it. Kind of easy but had to get jack lifts to do it myself, $30 at Autozone for a pair. Started the car twice and still got the CEL but I knew that it had to reset itself after a couple of cycles and I didn't want to disconnect the battery since I didn't want to lose my presets, etc. After 2 starts, the light turned off and everything is OK. Thanks for all the help especially to Jon316G.

Cool!~ so you got the code to go away with just a new 02 sensor form autozone. Did it ever comoe back? Im in Missouri just got the car about a week ago. Its been cold here and today while driving it got up to about 45-50 degres and the light came on. Went to Autozone and I got the same code CEL P0139. I hope this works for me. I dont think a good tune up has been done in a while and it get horrible gas mil. About 12 per gallon.

Hi sorry for the delay. I ordered the O2 sensor online and saved about $70 dollars in the process. I changed it and the code went away after the next cycle (6-8 ignitions). Ironic that about 1 month afterwards my cat went. My Mazda dealer read the codes, filled the warranty form and I got it changed for free. The warranty of the cat is mandated by the Federal Government and it is about 80K/8 years, FYI. Good luck with getting rid of your code!

I replaced mine with a NTK oxygen sensor, cleared the code (P0139), went for a long drive and the code is all gone. I couldn't get the OEM sensor, it was backordered at my local dealership. I'm at 97650km and the car is still going strong.