Oxygen Sensor Location

I have a 1997 Town & Country Lxi, the Service Engine Soon light came on and I run the test and the code came up 12 21 55.

I looked up the code and it is the Oxygen Sensor. My question is where is the Oxygen Sensor in the engine and how do I know which sensor needs replacing as I know there is two of them (I see the one going into the exhust pipe) but can't find the other one.

Thanks in advance
Gra

The Upstream Oxygen sensor is located just after the exhaust maniifold, viewable when the air filter box is removed. The downstream one will be located in the exhaust pipe, after the CAT.
The upsteam sensor usually goes first because of the nearness to the manifold (i,e heat).

Thanks for the help....I will check it out tonight after work

I have taken a look, I removed the air filter box but I can't see any oxygen sensor on the exhaust manifold anywhere. If anyone know's the percise location of this sensor, please could you let me know as I'm starting to go crazy looking for it lol.

Thanks
Gra

I guess know one know's where it is

I had the first sensor go bad last month and I replaced it. It is located about halfway down the exhaust manifold. I was only able to get to it from the bottom side which required jacking up my van and then crawling under it and reaching way up to it. It was a major pain to replace and I had more than a couple of bruises and scraped knuckles from replacing it. Hope that helps.

I just changed out both O2 sensors on my 97 T&C 3.8 liter V6. the upper one is located on the top side of the rear exhaust manifold. You can see it if you stand on the driver side front corner over the battery and look under (through) the space where the intake joins the throttle body. See it is about all you can do from here, and using a good flashlight helps. To access it, you need to run the van up on ramps and lay underneath. Get an O2 Sensor socket from any auto parts store (10.88 us$). I was able to unplug the sensor and attach the socket from underneath, then attach a 12" socket extension to the tool, also from underneath. Then went back topside under the hood and attached a 3/8" ratchet to the extension, which will be just barely sticking above the intake manifold by the firewall. I broke it loose, removed the socket wrench, then went back underneath to remove it by hand. Not really too bad of a job. It took me longer to line up the treads on the new one to get it started than it did to remove the old one. Hand was cramped by then. You can then re-attach the socket wrench and tool (without extension) from underneath and tighten it back up. Good luck with it.

Thanks to Losinit and hfarr for you help and advice. I have found the sensor and will fix it at the weekend.

Thanks again
Gra