Neither, that should be the sensor after the catalytic converter. Bank 1 sensor 1 would be the first sensor on the drivers side of engine. Bank 2 sensor 1 would be the first sensor on the passengers side of engine. Bank 1 sensor 2 would be the sensor after the catalytic converter.
The first sensor directly behind the drivers side exhaust manifold, it is threaded into the exhaust y-pipe.
Under the hood, on the firewall, drivers side.
if you are facing the truck it is on your left hand side of the motor, if you are sitting in your truck it is on the right side of the motor... the side the battery is on.
P0420 = Catalyst Efficiency Below Threshold (Bank1). Sounds like you probably need to replace the Bank 1 (drivers side) Catalytic converter.
Under the hood, passenger side firewall, not far from the blower motor.
It is on the left side of the motor up againest the firewall
Should be under the hood, on the firewall, passenger side, not far from the blower motor.
Yes.
under exaust manifold on passenger side
The number 1 piston on that motor is the first cylinder on the drivers side.
Under the hood, passenger side firewall, near the fan motor.
Under the hood, on the firewall, passenger side, close to the blower motor speed resistor.