2002 Toyota Sienna Ce V6 with air fuel sensor problem P1135 Help Please.?

Where is the Air fuel sensor located for 02 toyota sienna ce V6 ? i got a p1135 what other sensor should i replace ? i want to replace mine so i wont be charged so much money now the thing is i have a repair manual but i am confused because oxygen sensor is also the same as air fuel sensor so i am lost i need help finding out where exactly the Air fuel sensors are located.