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02 sensors and ses light

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Old Dec 13, 2006 | 07:20 PM
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Default 02 sensors and ses light

I have a 2002 trans am with longtube headers, catted y and loudmouth. When i first got the car, the ses light came on from time to time and then went off from time to time. I checked my cats and realized one was shot so i went to the muffer shop and the guy their just welded in a pipe for me on the left side where the cat was supposed to me, now the ses light has never went off, im guessing there was a bad o2 sensor before and now i dont no what the problem is, can you guys post pictures of similar setups and let me know what i need to do. im pretty sure its the o2 sensors and since there is a cat missing now, what do i need? and where to get them. sorry for th elong post
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Old Dec 13, 2006 | 07:48 PM
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oh and will bad o2's hurt performance.
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Old Dec 13, 2006 | 08:15 PM
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Well if I understood everything right it sounds like the problem is that there isn't a cat. If you removed one of the cats its going to throw a code for sure. You can buy new cats and put them in which might get rid of the code or you can get them tuned out. Heres a pic of my y pipe with high flow cats (FLP)
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Old Dec 13, 2006 | 08:16 PM
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you have no cat on the one side that will def throw a code. the front 02s are the only ones that will change performance the rears only tell if the cats are working properly.
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Old Dec 14, 2006 | 12:18 AM
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so if i change all the o2's and thats the problem, the ses light will go off? becasue i think they were all bad to begin with, which is why when they got to hott, the ses came on, what im asking is if the ses light is on, will it hurt performance. how hard to charge o2's
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Old Dec 14, 2006 | 12:20 AM
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and is there anyway around this without tuning or replacing the cat, because i love how it sounds with just one cat in the y pipe.
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Old Dec 14, 2006 | 11:16 AM
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back to top
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Old Dec 14, 2006 | 11:28 AM
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Bad or damaged 02 sensors will cause the car to run lean or rich...both of which are bad things for the cat, not to mention other things...so you need to get those sensors replaced first of all.

Second, running with no cat on one side will probably cause the SES light to stay on...you're going to have to get a tuner to tune that out of your computer if you want to stay in that configuration.

Lastly, I wouldn't run just one cat in the ypipe, that is going to throw off the backpressure and not be good for performance. If you are going to get rid of the cats get rid of the cats, but I would buy high flow cats and run those because they won't cost you very much hp and they would sound better than ory and get rid of any gas smell you might see with them off.
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Old Dec 14, 2006 | 11:32 AM
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Ok here's the deal. You have four o2 sensors total, two on each side. One is in the exhaust manifold (before the cat.) and one is after the cat. converter. The car's computer "looks" for a certain amount of difference in o2 after the cats compared to before the converters. If it senses readings are the same before and after the cats, it's assumes the cat to be bad.
So the point of all this is, if you remove a cat, even just on one side the PCM thinks you got a bad cat, and throws an DTC code (and turns the SES light on).
So you have three solutions:
1) have a cat put back on (which you said you did not want, so:
2) a number of our sponsors sell what is called an 02 simulator (or o2 sim for short) these take the place of the post-cat o2 sensor and trick the computer into thinkig a functioning cat is still there. or
3) have the post-cat 02 programmed out by someone with tuning software.

Edit: and like was said above, don't run just one cat, run either both or none.
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Old Dec 18, 2006 | 07:05 PM
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what kind of programmer, can i do it myself ?
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Old Dec 18, 2006 | 07:28 PM
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Handhelds will not permanently shut off the SES light. You want software. That will take care of the problem.
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Old Jan 10, 2007 | 09:43 PM
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The simplest solution would be to get an o2 sim for the catless part of the y, if like you said you want to keep only one cat on the car, then you would be done. Or you could get software to tune it which with your mods would be recommended. There's a forum specifically on the subject. I'm guessing your still on the stock tune if so your running rich and will foul the plugs eventually sooner than latter how long have you had the headers on the car?

Running rich, will that foul the o2 sensors or cats after some time?
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