Where is the oxygen sensor bank 1 sensor 1 on a Chevrolet 2004 Impala?

Answer 1

Oxygen Sensor

Some vehicles have (2) and some have (4) O2 sensors.
When you start looking at the O2 sensors, they are normally numbered something like "Bank 1 Sensor 1" Bank 1 is on the passenger side; Bank 2 is on the driver's side. Sensor 1 is the upstream sensor (near the frame, between the block and the cat) and Sensor 2 is near the Y-pipe (downstream of the cat).

Normally it is the upstream sensors (sensor 1) that go first. They see the harshest conditions.

You will need;

Oxygen Sensor Socket

Anti-Seized

Penetrating Oil

I have even used a small plumbers propane tank and heat it up and it help get them free.

Sometimes it will take 15 minutes or take a few hours it depends on your luck...