FgReed

iTrader: (2)

Hi Guys,
I'm new to both the LS1 and the forum.
I just purchased a 1999 Firebird Trans Am WS6
The person i bought it off had done some exhaust modifications. He put in an aftermarket y pipe without cats. He gave me the original y pipe along with the cats
My question is, is where would the 02 sensors be on the aftermarket y pipe. I don't really see them. From the reading i've done it says i should have 4 of them on the car. If some or all are missing, shouldn't my engine light be on?
I'm a bit concerned as i am going to eventually have to get an emissions test so i figured i'd have to put the original set up with the cats back on. The original set up has o2 sensors in the y-pipe.

Anyways, any bit of guidance or thoughts on what has been done would be appreciated.

Thanks in advance

Jay-P

iTrader: (16)

More then likely has 02 sims plugged into the original rear 02 wiring. These trick the ecm into thinking you have cat converters. Crawl under and poke around just before the y merge and see if you can locate them. They will probably be zip tied up somewhere.

They could also have been tuned out with tuning software.

gocartone

iTrader: (4)

Should still have the front two; they would be on the center side of the headers, around where the transmission meets the engine.

Chevycrew

iTrader: (1)

Yep stock fronts at the manifolds, rear were behind the cats in the Y pipe.

If your not throwing any codes, I wouldnt worry about the rear O2s

FgReed

iTrader: (2)

Thanks Guys,
I will have to have a look under there. It's really hard though because the car is lowered.

If the downstream o2 sensors are either sims or tuned out, will i need to hook them back up when i go to do my emissions? I know i'll need cats to pass emissions, but i wasn't sure about the downstream o2 sensors

Thanks again

gocartone

iTrader: (4)

Depends on where you live and how they test. Thankfully living in WI is good for some things, no checks here.