Ford 2009 E-150 Owner's Manual page 246

Roadside Emergencies
Removing the jumper cables
Remove the jumper cables in the reverse order that they were
connected.
1. Remove the jumper cable from the ground metal surface.
Note: In the illustrations, lightning bolts are used to designate the
assisting (boosting) battery.
2. Remove the jumper cable on the negative (-) connection of the
booster vehicle's battery.
246
2009 Econoline (eco)
Owners Guide, 1st Printing
USA (fus)