downstream O2
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Joined: Jan 2011
Posts: 66
downstream O2
I had my zzp dp installed awhile back and I noticed the other day the o2 sensor was put in on an angle an they stripped the threads of the o2 and the bung. So I took out the o2 and Installed a plug in there and my CEL light came on...The car runs fine but that wont effect at all correct?
Monte Of The Month -- August 2014
Joined: Sep 2008
Posts: 25,145
From: Southeast PA
That o2 sensor doesn't give the PCM any readings to adjust air/fuel ratio.
Shouldn't affect your car's performance, just is telling you that the cat isn't operating correctly (which a high-flow usually throws anyway)
Shouldn't affect your car's performance, just is telling you that the cat isn't operating correctly (which a high-flow usually throws anyway)
Nice to know we have such people here to get the precise info...
(we did have 1 that failed on the mrs blazer)
and her fuel mileage dropped off drastically..
Monte Of The Month -- August 2014
Joined: Sep 2008
Posts: 25,145
From: Southeast PA
For our cars, only the front bank o2 sensor (on the rear exhaust manifold) works with the MAF sensor and the PCM to adjust air/fuel ratios.
That 2nd o2 sensor ONLY monitors the effectiveness of the Cat and will throw the P0420 code if it feels the Cat is not operating correctly. Simply tune out that code and live life happy.
That 2nd o2 sensor ONLY monitors the effectiveness of the Cat and will throw the P0420 code if it feels the Cat is not operating correctly. Simply tune out that code and live life happy.
Joined: Apr 2010
Posts: 12,601
From: Mentor, Ohio
I'd be mad as heck that a shop installed it and stripped the threads. Man, that thing should have been super easy.
But Chibi is right, the downstream O2 is just to check the CAT, no performance/fuel issues and it can be tuned out of the PCM not to throw the code.
Verify your local emissions rules though, I've heard some places have been known to check the system for a cat AND the rear O2 sensor!!
But Chibi is right, the downstream O2 is just to check the CAT, no performance/fuel issues and it can be tuned out of the PCM not to throw the code.
Verify your local emissions rules though, I've heard some places have been known to check the system for a cat AND the rear O2 sensor!!
this is not 100% correct. there are some cars that when the rear O2 is removed, even when the code is removed from the pcm that have issues. it deals with a cat efficiency test. the car will rapidly throw more fuel to test the cat and will look at the rear sensor for a change in data. this causes the fuel trims to peg and noticeably hurt mpg. the only solution that i have heard is to have this test set to 0 runs vs the 6 it is set to stock. again this is not an issue on all cars... but some do react this way.
Joined: Apr 2010
Posts: 12,601
From: Mentor, Ohio
That is true, but that's why as Chibi said "for our cars" and explained the up and down stream O2 purposes. On our Montes, the downstream O2 affects nothing with emissions, fuel efficiency, drivability. It's there for a "health check" on the cat and nothing more.
No when I said some cars I ment to say some monte/GrandPrix have this issue. It is not all of them IIRC it was 2002+ that had the cat efficiency check. You won't get any engine lights the only way you would know there is a problem is if you are scanning and see te trims go to hell for no reason.
