Throttle body area

2000 tundra 4.7. Came out to a dead battery a few days ago. As soon as I hooked up my jumper pack I heard something either running or humming around the throttle body area. Ignition was off. Truck started and drove fine, battery charged back up (battery was 1 month old) after I got home and shut it off I went back under the hood and heard the same noise again. I disconnected the battery and went inside for 2 hours to do some research. Came back out hooked up the battery and the noise started again but while I was standing there a relay clicked in the relay box and the noise stopped. 3 weeks now and no more problem. Anyone know what this might have been? TIA for any info.

 

Probably just the ECM doing a throttle body adaptation after the dead battery. Nothing to worry about I'm sure.