So which o2 sensor is bank 1 sensor 2?

[Ttop34]

I made my custom post cat o2 sensor and I got a SES light today. Sooner than I have ever got one before, it usually takes a few days. Well the Autozone code was 140 which was a no activity out of o2 sensor bank 1 sensor 2.
Then after 3 times of getting codes for bank 1 sensor 2 before and them always telling me it was the post cat sensor, now they tell me it's one of the pre cat sensors. So can anybody tell me for sure which one it is?

[RacerJ]

You have 4 O2 sensors:
- Driver's side exhaust manifold
- Passenger side exhaust manifold
- Before the cat
- After the cat

Bank 1, sensor 2 should be the one right before the cat.

[Ttop34]

Are you sure about that? I've looked all over my Y pipe and I couldn't find anouther o2 sensor. Why would there be? It takes a reading in each exhaust manifold and then it takes it again right before the cat? What would be the point of that? Actually the Autozone guys said there were only three but I don't quite rely on their intelegence. If there really is one then please tell me where to look and I'll check it out.

[ July 10, 2002: Message edited by: Ttop34 ]</p>

[Magnus]

98+ models only have one after the cat I believe. Which would mean you have 3 O2 sesnors.

Bank 1 Sensor 1 is driver side manifold
Bank 2 Sensor 1 is passanger side manifold
Bank 1 SEnsor 2 is after cat

Bank 1 SEnsor 3 is before cat (for 97-)

[RacerJ]

My mistake. I thought all the 3.8s were the same. But the sensors are *supposed* to be numbered in order as they go back.

So shouldn't the sensor right before the cat on a '95-'97 car be Bank 1, Sensor 2? It SHOULD be...

[Magnus]

I thought it should be as well.. but if my memory serves me correct 2 is AFTER the cat and 3 is before.

I could be wrong though.

[TheBlackSwordsMan]

There are two pre-cat sensors and one sensor after the cat. I got a O2 sim when i ripped that bad boy off. After awhile I tired of the air sound that was coming out with the exhaust its really hard to explain what it sounded like. It made my car sound like a old truck from the outside lol. I say go with a high flow cat because it doesn't make it quiet at all.

[Ttop34]

Ummm..., I'm not really asking for suggestions here on what to do with my exhaust, but thanks for your input anyways.
What exactly do you mean by "ripped that bad boy off"? Did you snag it on something while going off roading or what? Run over a small animal?
That noise of the old truck, did you just have a whole in your exhaust or did you have the old o2 sensor still plugged in? If nothing was there then that's called an exhaust leak and it makes a putting sound like a old truck or go cart.

Well since you don't know my entire story here it is in short abreviated form. I took the cat off and got an incredible gain from it. I had an o2 sim that kept giving me a SES light and saying low voltage which I still have no idea what that crap was. I found instructions how to build a custom o2 sim so that's what I'm doing. It hasn't exactly been cost efficient because I paid an outragous $40 to get the o2 sensor put back in. But if that had been cheaper then this would have saved me a lot of money but I still have to sell my o2 sim to actually make that back. When I finnally figure out why nothing is getting through my resistor then I'll post instructions oh how to build this to save everybody $50.

[TheBlackSwordsMan]

I took the cat off and put a straight pipe there. The weld job we excellent so I dont' think I had any leaks. I put the high flow cat on and the sound went away so I dunno, just letting you know that that's how mine sounded with no cat. You might have had a bad 02 sim by the way.

[Ttop34]

Well not sure what you mean by old truck then. Maybe the poping sound of open exhaust? Anyways, I was testing my o2 sim back when I still had a cat on and it gave me a low voltage code so I sent it back and exchanged it. I got the same code with the new one. Just talked to ThunderRacing and they had no clue why I would get a low voltage, Casper Electronics said it might be a fuse though so I'm going to check on that as soon as I figure out what fuse it would be, anybody know?

[ July 12, 2002: Message edited by: Ttop34 ]</p>

[Cale]

I exchanged my 02 sim as the first one gave me low voltage... and im still getting the code. So im in the same boat as you.

[RacerJ]

Just FYI for whoever:

Today I ran across some technical printouts I had buried in a pile of junk, and they state that on the '96 and '97 3.8s, the sensor before the cat is Bank 1, Sensor 2; and the post-cat sensor is Bank 1, Sensor 3.