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Discussion Starter #1
Sorry to make another thread on this, but just a quick question. If my o2 sensor is causing mpg issues, would it be the upstream or downstream one? (or could be either?)

As I refereed on my other thread, I have a few other things I'm looking at, but just trying to get more details on that one particular "could-be"

Thanks!
 

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If you have a bad HO2 sensor it will set a code telling you which one is bad.
 

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yup that's true, once it gets past a certain value range the pcm will set off the light.

My rear o2 died and dropped me about 7mpg's. When my front screwed up I honestly didn't pay much attention since the light illuminated on my way to work and it was fixed the same day after work, but normally the upstream kills mpg in most vehicles.
 

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Either HO² codes will make "PCM" or "ECM" go to a preset value matrix always causing your car to be harder on fuel.
 

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Discussion Starter #6
yup that's true, once it gets past a certain value range the pcm will set off the light.

My rear o2 died and dropped me about 7mpg's. When my front screwed up I honestly didn't pay much attention since the light illuminated on my way to work and it was fixed the same day after work, but normally the upstream kills mpg in most vehicles.
That would be the hard to get to one in the header wouldn't it. :(

poo
 
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