It has 4 total.
The 5.2L has two oxygen sensors.
There is 2 oxygen sensors on the 2002 Nissen altima
there are 4 o2 sensors
they have 2 o2 sensors on the muffler ELIA
The 2002 Toyota Camry XLE has four oxygen sensors. There are two sensors on the exhaust manifold ,and one before and one after the catalytic converter.
THERE ARE 2