I know what a code 41 is, it's a TPS error. But what is it exactly? What causes it? How can the computer know the TPS is not calibrated properly if the engine isn't even on and the engine isn't idling?

I've been fighting TPS issues for what seems like 2 years now. I had adjusted the TPS and had no errors for the longest time. Now when I check for codes, I get code 41. Nothing else, just 41. I'm trying to get it code free.