I didn't have any codes or lights when I replaced my sensors but they were still out of spec. Man, if both your sensors read 0 I would say that's out of range! My *guess* is that your sensors need to be replaced, they don't last forever...some info on that here https://www.automedicsupply.com/faq.php?#change I think you might want to remove one and test it inside at room temp to be sure.
I'm not sure really, the repair manual isn't always clear, but I would assume they are saying the sensor should be at room temp. I took my reading inside on the bench, at room temp.