rattling noise

What is your question?

wheneve I put my 2002 dodge grand caravan sport in gear I hear a rattling noise but as soon as i rev it up or put it in park the noise goes away. I've been told it's the belt tensioneer but it's been making this noise for two years with no problems. I think if it was the tensioneer it would have gone out by now. The check engine light is not on. Any ideas? I'm trying to sell it but with these noise i'm afraid i won't be able to. Thank You