o2 sensor placement

[98D22]

my 1st o2 sensor is in my header (same place as the stock exhaust manifold). my question is this. there is a flange for the second o2 sensor on the colector of the header; which is BEFORE the catalytic converter. here's the rub. when i got my muffler and my pipe coming from the collector welded, i was told the 2nd o2 sensor should be AFTER the catalytic converter.

where is your 2nd o2 sensor, pre or post catalytic converter?

[02GreenFronty]

2002 2.4L 4 cyl... 2nd o2 sensor is before the cat.

http://i25.photobucket.com/albums/c88/BS1981/exhaust.jpg

this is looking under the frame from below the driver's door


and which headers do you have? I have a pacesetter header (not installed yet), and the only 2 flanges that are on it are for the o2 sensor (on pipe coming off of cyl. 3) and the EGR tube (long horizontal pipe coming off cyl. 2)

[double deuce]

0n my frontier the downstream o2 is post the first pre cat. However since you're using a header id either mount it behind your cat, or get a o2 simulator.