HP LaserJet P4015 Printer series - Manual (Page 181)

Clear jams from the optional duplexer
1. Lift the optional duplexer up and then pull it out to remove it.
2. Remove any paper that is on top of Tray 2. (You might need to reach inside the product.)
3. Slowly pull any paper out of the optional duplexer.
ENWW Jams 169