Where is the o2 sensor that controls the idle . for a 2002 saturn vue

Question edited for clarity.
Question moved to model category.

As a general rule, with a laterally positioned V6 , Bank 1 is always closest to the firewall Bank 2 is closest to the headlights.

Sensor 1 is ALWAYS the one in the Exhaust Manifold, and Sensor 2 is ALWAYS the one AFTER the Catalytic converter.

confirmed here

02 sensor "bank 1 sensor 1" - Saturn Vue

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Mar 12, 2015 - Bank 1 is on the firewall side. Sensor 1 is in the Exhaust Manifold. Chazberry is offline ...

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2 x oxygen sensors --one after each cat converter
there are also 2 x heated oxygen sensors ( different operation and reporting system) that are before the cat converters or in the exhaust manifolds run the fault codes to find the faulty sensor and it probably isn't either o2 or ho2 sensors

having PO 304 = Misfire cylinder 4,PO 306 = Misfire cylinder 6, as I read above you have done the most. The thing that you have missed is to check whether the Catalytic Converter is faulty or not. To get an idea check whether you have a smell like rotten eggs at the end of the exhaust,you start having problems with cat and needs replacement. My advice before you go for a cat replacement is good to visit an MOT center and check your emissions and then you decide,

I have had that problem on other vehicles and it was the o2 sensor

curious to know if you got this solved. Guessing downstream o2 sensor. did your vue idle high? act like it was getting too much gas? Let me know please.

I had exactly the same problem .Mine was corrected with replacing the O2 sensors .The sensors cost less than $30 each but cost about 20 mins labor per sensor .So if you got an honest mechanic the total cost will be around $130 .

should be right behind the cat converter

make sure you have no hoses on the engine that fell off listen for a hissing at idle. If all ok and you checked for codes which should be done before any parts are replaced then the most likely cause is the Idle Air Control Valve. (IAC). IAC's usually wont set a code.

check the cranshft position sensor and the idle position sensor.

The code doesn't say that the O2 sensor needs to be replaced, it is telling you the O2 is showing that the fuel system is either to rich, (to much fuel) or to lean (not enough fuel), so the sensor is not the issue, most likely something is either wrong with the fuel injectors such as dirty nozzles or there is a vacuum leak or one of the fuel control sensors like the MAF has a problem, it can and is very difficult to sort this out, the Saturn dealer has the diagnostic equip to get the root cause of the problem, are they the ones who did the work? if not take it to Saturn and even though they cost more they won't spend as much time to find the problem, outside shops can't afford this special testing gear, cost is way to high, about $50,000 for the electronic service bay diagnostic systems Saturn has. One last point the computer or PCM as we call it is very rarely the problem, about 4% of the time in fact, very low failure rate.