What is diagnostic code 27 on a 93 Toyota pick up 22re?

I just ran a check on my Toyota and got code 27. from what I have found my code reader says "HO2S rear circuit" and I have read that it is an "oxygen sensor or circuit."

I am assuming it is my rear oxygen sensor since in the Haynes manual, CA, is in parenthesis after the code 27.

good luck

I am a little stumped right now myself. I think I am going to order the rear sensor, change it and reset the code to see what happens.

cheers