My buddy has an 05' Cummins with a bullydog programmer on it...The box says the programmer will work on cummins from 03-05....whats the difference bettween an 02 to an 03 cummins....I know theres alot but why wont a box hook up to one??? THe reason im asking is that we were gonna hook it up to my truck but noticed that it was only for an 03 to an 05....

 

Your truck is a 2nd gen and your buddy's is a 3rd gen, Cummins 600 i think.
I'm pretty sure that the computers are totally different. and if wrong i'm sure i'll be corrected.

 

Two completely different animals. 02=VP-44 05=HPRC
The electronics are diffent.
CJ