Can anyone tell me where the upstream oxygen sensor is located on a 97 Dodge Stratus? I am getting error code 21 and I have changed my downstream sensor - found it without much difficulty. Does the upstream one look identical to the downstream? I see some sort of sensor in one of the 4 pipes coming off the engine block (the exhaust manifold) but it looks very different from the downstream sensor - oblong looking with a couple of screws that hold it in rather than the sensor bolting itself in.

Gotta get this to pass CT emissions!

TIA

 

Can't believe no one has had to replace that. OK, I'll answer myself (for the benefit of others) as I found out the location. It is in the back of the engine where the manifold comes out. Looks almost inaccessible or very tough to get any kind of leverage on a wrench to remove it. Anyway, I am going to try to access it from the top rather than from underneath.