Bravo Star Greg Plitt -- Life After Death ... On Bravo

Bravo star and fitness instructor Greg Plitt will live on after death ... we've learned the network will air the episodes he shot shortly before his death.

Plitt -- who was hit by a train Saturday -- shot multiple episodes for "Friends to Lovers," which features 2 friends who attempt to take their relationships to the next level.

Production sources tell TMZ ... the network will air 3 to 4 episodes in which Plitt tests the waters with long-time bud Melanie Marden.

We don't know if they hook up on the show, but everyone involved knows it will be tough for Melanie because she'll have to go solo promoting the show.

We're told the episodes will hit the air in the next few weeks.