Need some help, 02 sensor confusion
AFS75 is the p/n for AC Delco pre-cat sensor. People say they "changed" the design in the past few years because they look different from the factory ones. Factory is up top, new AFS75 is bottom.

But it really sounds like BS because here's what the Denso 2344012 sensor looks like. It's 2/3 the price.

You probably get Densos in an AC Delco box.
Bank 1 sensor 1= side of engine for cylinder #1 and sensor before the cat
Bank 1 sensor 2= side of engine for cylinder #1 and sensor after the cat
Bank 2 sensor 1= side of engine for cylinder #2 and sensor before the cat
Bank 2 sensor 2= side of engine for cylinder #2 and sensor after the cat









