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.