Need Help... Beeping Sound

I have an '00 Excursion 4x4 and I need help troubleshooting a warning beep. After I start the truck and put it in gear 5 seconds later there is a warning beep that beeps five times: beeep---beeep---beeep---beeep---beeep then pauses 5 seconds then beeps five times again for 4 more times.
Its NOT the seatbelt warning and there are no indicator lights on the dash showing what it could be.
The sound is coming from the fuse box above the pedals.
It beeps even if I put the truck in gear and just sit there and no move.
I checked all of the fuses and the sound is just driving me crazy! please help me!








