Headers and O2 sensors
Headers and O2 sensors I bought my car about a month ago and the SES light keeps coming on, previous owner stater because of the 02 sensors and the headers. I thought that I did not have any rear 02 sensors. I finally got to crawl under this beast and noticed I do have all the 02 sensors. There are 4 total. 2 on the end of the Kooks LT Headers and 2 after what I believe is high flow cats. Of course it would be nice if I put the codes up but off hand I can't remember right now. I will have to get them at my lunch break, but in the meantime does anyone know why the light would be coming on?
could be from anything but if the previous owner is right then one or all your o2's could be bad and causing the SES light to come on. Best bet is to scan the codes and see what comes up. If you are getting bad gas milage, then it is probably an o2.
Thanks I will get the codes at lunch, have the scanner in my car. My gas mileage is around 15-17 city mpg, and maybe 18 highway, was hoping it would be better than that. Got to get the codes! Thanks.
Report back to us on the codes. 
Downstream O2's (after cats) usually still throw a red flag even if cats are on if the cats are aftermarket. This would be your SES light.
The front O2's sometimes go downhill and begin to make the car run rich after headers. Most people's untuned cars run a bit rich after boltons, which can/will decrease mileage. If they front O2's are trashed, they may be the ones throwing codes.
If your rears are setting the SES light, you can either TRY to find some O2 sims, or have the codes tuned out by a speedshop with LS1edit/HPTuners/EFIlive. I'd recommend buying the program and doing it yourself, you'll then be able to tune everything on the car. It's really enjoyable/easy once you learn a few things and play with it.
Downstream O2's (after cats) usually still throw a red flag even if cats are on if the cats are aftermarket. This would be your SES light.
The front O2's sometimes go downhill and begin to make the car run rich after headers. Most people's untuned cars run a bit rich after boltons, which can/will decrease mileage. If they front O2's are trashed, they may be the ones throwing codes.
If your rears are setting the SES light, you can either TRY to find some O2 sims, or have the codes tuned out by a speedshop with LS1edit/HPTuners/EFIlive. I'd recommend buying the program and doing it yourself, you'll then be able to tune everything on the car. It's really enjoyable/easy once you learn a few things and play with it.
Staging Lane
Joined: Aug 2007
Posts: 55
Likes: 0
When you get the codes, If its the fronts its probably due to running rich and mucking the O2 sensors. If its the backs its because the cats aren't lighting off w/i spec so it triggers the SES.
I had my downstream O2's defeated as part of the tune. You will continually get the SES, it can be reset but it will reappear.
I had my downstream O2's defeated as part of the tune. You will continually get the SES, it can be reset but it will reappear.
Last edited by CaptainSS1; Oct 17, 2007 at 10:24 AM.
With computer tuning the code can be set to not go off no matter what. You could light the O2's on fire and the SES light wouldn't come on. This may be your only option as the EPA has been cracking down on O2 sims.
Staging Lane
Joined: Aug 2007
Posts: 55
Likes: 0
In my situation, it was a workable option because I drive my car under 5k a year and the inspection stations that are also speed shops choose to interpret the law and render my car "Emission Exempt" . Not sure what someone does IF they actually have to pass full blown inspection on a DD.
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Verdad Gallardo Alright did a search and alot of reading this is what I found. Front O2s are fouled or bad. I am going to get a propane torch and try to clean the front ones and see what happens-if not I will replace them with Densos?. Car does seem to be running rich, and I do have bad gas mileage and idle is rough. Hope my ET will improve...I ran a 13.3 with these o2s a couple weeks ago...Hoping for 12s!!!
