When I was a kid, the #1 Cylinder was the left front cylinder, which by my logic makes the Bank 1 on the left side of the engine. I have multiple reference manuals from right after the guy invented the first wheel that say the #1 is the front cylinder on the left side of the motor, but these all make reference to cubic-inch engine displacements.
It seems that today the designation of where #1 is has changed -- along with metric designations for displacement -- and that Bank 1 might actually be on the right side now.
I have a 5.8L V8 motor, and I have a Check Engine light that means that the O2 Sensor has detected a lean condition in Bank 1. The check light may or may not come on in any given trip, and it may go out on its own after coming on. I was getting ready to replace the O2 Sensor (actually called a Heated Exhaust Gas Oxygen sensor) when I realized there are actually two of them. I suspect they are both the same, but there are three part numbers that vary according to how long the pig-tail is. Selecting the right sensor is part of getting the wire harness right. My truck uses far too much fuel to be running lean, therefore the O2 sensor must be on its way out.