You can look up all OBD2 trouble codes on thsi site:
http://www.iequus.com/support/obd2_definitions.php
My guess (from reading these codes) is that he is replacing the air/fuel sensor. It's a more precise device for monitoring the air/fuel mixture on California emmision cars, instead of an O2 sensor. Perhaps someone who has more experience with California emmisions cars can correct me if I am wrong.
Mike