We had a rattle in our 2004 ES that lasted for months, it was absolutely infuriating. The dealer worked on the rattle several times and never could solve the problem. I happened to be in Albuquerque and took it to the local Lexus dealer. I drove around town while a mechanic sat in the back seat to isolate the sound. When we got back to the dealership the mechanic went inside came back with a can of belt dressing. He spayed the door jams on both back doors and cured the problem. We never had a rattle again. What we though was a rattle turned out to be a squeaking noise caused by the seal rubbing against the door jam. This was a real simple fix.