sensor problemo

so my maine registration ran out in october and now, in order to register it out here in Utah, i need to pass safety AND emissions. problem is that my check engine light's been on ever since we turbo'd/swapped motors waaay back. i mean it had come on and off a lot after the header was put on, but now it's stayed on since last october. working at Jiffy Lube, with an I/M bay, it should be easy to pass, but there isn't much you can do to trick the comps no matter how nice you are. i've run an obd2 check, came up with the a/f 02 sensor, the pre-cat one, so i went to pep boys and got a $90 replacement, put it on at work, ran it again after turning off the light, and it came right back up with the same code.
me and a coworker ran some tests since i dunno much far as electronics, and the voltage wouldnt change when we revved it while the 'ce' light's on, but he turned off the 'ce' light and we revved it, and the voltage changed...up until the 'ce' ligh popped back on, then the voltage was steady again no matter how much we revved. we figure that's the safe program coming on, where it runs a pre-dtermined a/f setting and acts like the sensor isn't even there, resulting in crap gas mileage.
now i'm wondering what all this can mean exactly. could i just have gotten a bad sensor (i know there's a 50/50 chance from any other than honda), or could it be a bigger problem? i need to know ASAP cause i risk big tickets for expired plates!
Any suggestions welcomed! Thanks

Honda's kick back just about anything but a Honda sensor. By pre-cat, you mean upstream that is in one of the runners of your header, correct?? Is/was your car ULEV??

yea, he had a ulev motor, the a4, and i think he swapped in a regular vtec motor, the a1.

hows your cat doin? i know mines done for now, haha, but a while ago i used to get codes for catalyst system sh!t.

sketch is right. i got the 02 that was meant for the lev motor just in case it allows more leeway, you know? should i have gotten the ulev sensor so it matches up better with the ecu?

if your not to worried bout how it runs just have someone else put thier car on the machine and get it to pass that way.

if it was the cat sensor there's a fouler trick you can perform. not sure about the one on the runners.

acrod99 said:

sketch is right. i got the 02 that was meant for the lev motor just in case it allows more leeway, you know? should i have gotten the ulev sensor so it matches up better with the ecu?

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I would give that a try, the ULEV sensor since your running the ULEV ECU.

yeah, i can imagine the emissions from a LEV compared to a ULEV aren't very noticeable. there's only 2 hp difference in the engines anyway. i will contact a dealer and ask which i should use and purchase one soon.
on a side note-does anyone think it could be something other than needing to change that sensor again?

What's the exact code??

Also, don't listen to a Honda parts guy, they do not know what they're talking about.

all 02 sensors are the same regardless of make and model... only difference is the wire length and connector type... it's weird tht the sensor only works with the CEL on