Where are the 02 chevy impala 3.8L o2 sensor locations, I only see three. the top bank one sensor 1 is stripped out, how do i get that one out?

SOURCE: 2002 Pontac Grand Prix GTP P0171 code engine stumbling at times

Bank 1 is the frt side exhaust manifold (did they say bank 1 sensor 1?),you can start by replacing that sensor,i would check the intake for leaks ,the gm 6cly. are known for bad intake gaskets,you will see oil coming out form the frt or rear of the intake,also check your atifreeze overflow bottle for bronwish sludge,which means that the oil is mixing with the antifreeze.A leaking intake could cause that lean condition.

SOURCE: location of the bank 1 sensor 2 O2 sensor on a 2001 ford escape

B1 means the sensor is located on the same bank of the engine that has the #1 cylinder. B2 is located on the opposite bank.
S1 means the sensor is located BEFORE the catalytic converter
S2 means the sensor is located AFTER the catalytic converter

You didn't say which engine you have, so I've included the diagrams of both 4 cyl and 6 cyl so you can see the banks

SOURCE: need to locate o2 sensor location bank 1 sensor 2

You need to check two things.

First, there is a heat shield on top of the front of the motor where the o2 sensor you already replaced is. It's got (4) 12mm bolts. Remove it and check the exhaust manifold (big thing you put the o2 sensor into) for cracks. If there are any cracks, you'll get o2 sensor codes. Replace the manifold.

Second, if the manifold is fine start the car and listen to the exhaust pipe under the engine for leaks. Or if you already know the exhaust is loud... that's gonna do it too. A leaking exhaust pipe on an Accent will set secondary o2 sensor codes.

SHOULD you try to change it yourself, you will need a 7/8" wrench, and a new o2 sensor, or flex pipe, or manifold depending on what's broke. Do NOT touch the tip of the new or old o2 sensor to ANYTHING when you take it out or install it or it will be ruined permanently. Run the car until it's at it's normal operating temperature. Raise the vehicle, and take the o2 sensor out of the car (see below to understand which one) using the 7/8" wrench or if you got fancy and bought an 02 sensor tool... use it.

Replace whatever parts are bad (manifold or pipe) or just replace the sensor you need. Then restart the car and take it to a parts store and have them clear the code. The code (and check engine light) won't return right away, it usually takes a few days. If you did everything right you should be good. If not, it's not a terribly expensive job to have done and by now you should be able to explain to them what's wrong based on what you found when you looked at the car. Just tell them everything you checked and what you saw.

Education: I'm not sure where that half baked answer about o2 sensor 1 being near cylinder one came from but here's the real deal.

Sensor 1 is always BEFORE the catalytic converter
Sensor 2 is always AFTER the catalytic converter

Bank 1 and Bank 2 refer to which SIDE of the exhaust on 6 and 8 cylinder engines. Bank 1 is usually left side, Bank 2 is usually right side.

So... O2 sensor B1S1 refers to the O2 sensor BEFORE the converter on the LEFT side of the motor.

SOURCE: Code p0141 02 Sensor Heater Circuit Malfunct Bank #1 Sensor2

after the catalytic converter on the driver side in the exhaust pipe.

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SOURCE: where is the oxygen o2 sensor located on 2004

There are 2 oxygen sensors on the 2004 Impala, located under the car near the CAT converter.

Jack up the passenger side or onto ramps to make easier acess.