B1845 code engine won't start every time, esp after sitting for 1 hr on 2000 Ford Expedition

2000 Ford Expedition won't start all the time, esp after I
've been out of truck for 45 min or so. lights ok, battery ok, just doesn't start, diagnostic code B1845. I tried entering my key manually lock and unlock. no solution here.
Help me, please, Momma needs to get kids to school, dance, and grocery shop.

Asked by for the 2000 Ford Expedition