Dodge 2015 RAM Owner's Manual page 262

260 STARTING AND OPERATING
Emergency Fuel Can Refueling
Most fuel cans will not open the flapper door.
A funnel is provided to open the flapper door to allow
emergency refueling with a fuel can.
Diesel Fuel And DEF Fluid Filler Door
1. Retrieve fuel funnel from the jack kit located under the
front passenger seat.
Fuel Fill Funnel Location 2500/3500 Models
2. Insert funnel into same filler pipe opening as the fuel
nozzle.