I don't think there is a code.
But i know a few methods to get the Pokemon.
1.you can trade it from Pokemon Platinum,Pokemon Diamond,or Pokemon Pearl.
2.In Pokemon,Platinum,Diamond and Pearl there is a Pal Park,(You need national dex),which you can get your old Pokemon from LeafGreen,FireRed,Ruby,or other Role-Playing Pokemon games.
3.there is a code,a Pokemon modifier,were you can get Pokemon 1-493.
I hope i helped
if you look on Google for "heartgold deoxys ar codes" it should be the 5th link
Chat with our AI personalities
If you have action replay you can get any Pokemon you want. This feature works only in Pokemon Heartgold , Soulsilver and Platinum.
There's no Action Replay code for Zoroark in Pokemon HeartGold, because Zoroark does not exist in Pokemon HeartGold.
There is not a known Darkrai Action Replay Code for Pokemon HeartGold and SoulSilver yet.
If You Want A Deoxys In Pokemon Platinum ,Migrate,Trade,Or Use The Action Replay Pokemon Modifier.
By Action Replay