What does lack of upstream heated oxygen sensor switch - sensor indicates lean - bank no 1 mean?

Answer 1

Oxygen Sensor

There are actually (4) O2 sensors on your truck. If you look inside the wheel wells behind the fender liner, right about where the frame is one O2 sensor, the other is underneath the truck about half way back in relation to the transmission. If you see where the exhaust joints together, you went about 6" too far.
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…