It is an 02 sensor. It just tells the computer to modulate the air diverter valve so that it will modulate air being injected to the exhaust manifold. That's all it does since the carb doesn't do any adjustments other than manual screw adjustments. If the o2 isn't working the air injection may run all the time and causse your NOX to read high and fail. But if your o2 sensor is good then be sure that the electric diverter valve is good and working too.
