Bank 1 Sensor 1, O2 sensor on the 2003 S-10 with the 4.3L engine would be located in the exhaust pipe immediately after the drivers side exhaust manifold. It is best reached from under the vehicle.
Bank 1 would be the bank of cylinders that contains the number 1 cylinder. The bank 1 sensor 1 would be the first O2 sensor threaded into the exhaust system after that bank of cylinders that contain the number 1 cylinder.
Need more info, is this the 4 cylinder or 6 cylinder engine and which sensor on bank 1.
Bank one is the side of the engine with cylinder #1. Sensor 2 is after the catalytic converter.
bank 2 is opposite #1 cylinder and sensor 1 is front.
If I am correct, bank 2 sensor 2 is opposite the #1 cylinder in the rear.
YES
Bank one refers to side where ! 1 cylinder is and the sensor 2 is the rearmost(at the converter outlet).
Downstream ... This is after the Catalyst Converter.
Bank 1, on a 4.3 L engine would be on the drivers side.
Find cylinder one, usually on the driver side. That is Bank one side, then go to the second O2 sensor, which will be the one after the cat converter.
Bank 1 is the bank of cylinders that has contains the number one cylinder which in your case would be the drivers side bank of cylinders. The O2 sensor for bank 1 sensor 1 is located in the exhaust pipe directly after the drivers side exhaust manifold.
It will be the lower of the O2s (furthest away from the engine on bank one). If its a v-6 bank 1 is usually where the # 1 cylinder is.