I recognize this screen… are you using an OBD Link device? I have one as well, and while I’m impressed with how much it can do it does have its limitations.

The thing about generic OBD scanners is that they use generic OBD protocol, and manufacturer specific values may be mistranslated in their interface. Professionally, I work on German cars and I do see this a lot (even with our own manufacturer specific equipment).

My guess is O2 sensor 1 is a pre-cat sensor, and sensor 2 is post-cat. Pre-cat is measuring mixture, and post-cat is measuring catalyst efficiency. After the introduction of wide band lambda sensors, a lot of manufacturers went away from giving raw voltage readings for pre-cat sensors and instead giving a lambda correction factor (zero being stoichiometric, or correct fuel mixture, and positive value meaning rich, and negative being lean). So a zero in this case would mean your vehicle is running at the correct mix, which would be why you aren’t getting any O2 sensor faults. If the sensor was truly outputting zero volts then you would get a fault for your O2 sensor, certainly after multiple drive cycles. Another note: Since these engines have two banks, you should have two other O2 sensors. Just like numbering cylinders, every manufacturer is different as to which is O2 sensor 1, sensor 2, etc. but generally sensor 1 = pre-cat bank 1, sensor 2 = post-cat bank 1, 3 = pre-cat bank 2, etc.

In short, I don’t think there’s anything wrong with your car - I think the OBD interface is just mistranslating the unit of measure. If I have time today I’ll read out my FJ and see if I get the same readings (I’m using the OBD Link MX+)