02 sensor and cat

[Isaurio]

I have a quick question. When i put my full magnaflow cat back system i noticed the o2 sensor is before the cat. Does’ suppose to go after the cat? Also i have OBX headers meaning no pre-cat. No check engine code came up for like 3 month now. Does it affect the engine performance? It seems that the second 02 sensor is reading the same numbers as the first o2 sensor the one on the headers. Any advice? thanks

This is for a 02 2.4L

[Isaurio]

dam. BUMP BUMP

[littlerick]

my 03 doesnt have 1 after the cat, only 1 before it.

[minesbroken]

my 03 doesnt have 1 after the cat, only 1 before it.

my 03 has one on the exhaust manifold and one after the cat.

[Isaurio]

Yes thanks. I was talking to a few members and correct the o2 sensor has to be after the cat. I have to change it around. Crap.

[Conjee]

There is 1 02 Sensor before the Pre-Cat and 1 Sensor after the pre-cat but before the main cat. Reason the readings are the same is because you have headers, this eliminates your pre-cat. Engine code lights up because it is sensing this. If you want a temp. fix you can use 2 spark plug nonfoulers, drill a 1/2" hole in one of them then screw your 2nd o2 sensor onto it. This should eliminate the check engine light. At least it did for me. I bought the Help! Brand Part# 42009.

[Isaurio]

I dont have any check engine light. I know about header you eliminate the precat. O2 sensor is on the headers. My question is. 02 sensor goes in front or on back of the cat. Right now mines o2 is on the front of the cat.

[Isaurio]

I believe is the 02 is bad location because, My car when is on drive it vibrates a lot "more than normal. I changed all motor mounts like 8 month ago OEM ones. Also it hesitate on acceleration when car is on operating temp. I was reading about bad readings of 02 sensors and it says about those problems. Anyone having problem with new headers and full cat back system. Post pictures of your setup.