o2 sensor on 2.4 2000 galant and Engine wiring harness

Car started throwing a fuel trim code so i decided to replace both o2 sensors,from reading the haynes manual, there are two o2 sensors upstream and downstream, i've located the downstream but can't find the upstream. it's supposed to be located on the front exhaust but i don't see a o2 sensor nor a connecter to hook one up two, also i don't see a hole for one.

also just wanted to ask if anyone has replace a engine wring harness for this vehicle, if so how hard is it ?

any help would be appreciated, thanks in advance

anyone have a similar problem?

Not sure about fed spec but cali spec cars have 4 oxygen sensors on V6 models and 2 on the 4cyl models.

There is one sensor before the precats and one after the precat but before the main cat. Again this is cali spec info.

Thanks for the reply, yeah I don't think model I have has 2 o2 sensors, theres just one downstream one

4 or 6 cyl?

4 cyl

I'm in California so, someone with Fed Spec knowledge will have chime in on this one.