Code 13 refers to an open circuit, not necessarily a bad sensor.
Code 14 could be a overheating problem, What condition is your radiator in? If it is old and clogged, you will have overheating problems.
I have the same service manual...I should have mentioned that....the O2 sensor was 20G miles old which is the only reason why I replaced it, and the radiator is in good condition. I did take it to a shop and had it properly cleaned and tested. They said it is running at 80-90% efficiency, up from about 30-40% when the car overheated.
I don't have a digital ohmmeter....unsure how else to check it.
Further, the "scan" tool won't communicate with the car....but that is another problem...(new Innova 3120)