what is causing battery to drain?

Truck would not start
..jumped it w/my car…started fine…the battery in my truck is new.I let it charge off of
the car 20 min. Every thing seemed fine..no warning lights..idled great..tranny went into
all gears..breaks worked…guages all registered. BUT….when i take the jumper cable
from the car off the truck will not stay running and the battery is dead shortly there
after.First thing i notice is the ABS warning light comes on…then airbag warning light!
What ever the cause it
drains power from battery  and the
the engine dies. What is causing this? Truck sat most of the winter and when i drove it
this spring the brakes were some what noisey but quieted down after awhile! I figured
they had to be a little rusty nothing to abnormal! Problem truck is having seems to have
something to do with the brakes! They have fluid and the foot petal pressure seems
normal but thinking the ABS sensor is the culprit! Forgot to mention all fuses seem to
ok.. did not find any that had burned out or broken!
awhile!