I own a 1996 Honda Accord and just recently got a new catalytic converter and o2 sensor installed because of 1 CEL code. The mechanic reset my OBD System after the installation to remove the CEL light which never came back on (its been a weak). The same day this procedure was done is the same day I wen't to MVC to receive an inspection, I failed only because the OBD System, was not ready (no other reason). They told me to drive the car around for a while. I ask if disconnecting the positive terminal of the battery (not the ground) will reset the System because I disconnect the positive terminal every night. I know this is not good for the car but it is only temporary until I find the reason my AC lights won't shut off.
Read more: Does a cars OBD System reset everytime you disconnect the positive battery terminal?