[patrickt]

The dealer will have a special tool for that car for a parasitic test. Maybe a code has been thrown that does not set the dash light? That's what you hope for, and their scan tool will spot it. If the battery passes the load test, and the charging system passes the charge test, then a parasitic drain is the only option. Most modern day computer systems have parasitic protection build in to the coding (like if you leave the dome light on). It still wouldn't hurt to look at the car in the pitch black of the garage and see if you can see a light coming from the trunk or glove box. That only happens once in a lifetime, though.