No. Oshawatt is not present in Pokemon Diamond.
Oshawatt is a Pokemon only available in Pokemon Black and White. There is no way to get it in Pokemon Platinum, because that Pokemon didn't exist when the game was made.
Action replay
Action replay is not an Pokémon item that can be obtained in Diamond.
No
Go to neoseekers.com
no you have to get is from an action replay or go to a Pokemon event
action replay
its a cheat
action replay
Action replay.
action replay
action replay