There are a couple common causes for parasitic drain. One is the TCM and the other is Nav if you have it. If you are getting parasitic drain, pull the fuses and if you don't have a dead or near dead battery the next day, plug in one of the fuses and wait another day. If it's dead, you found your culprit. If not, you plug in the next one and give it a day. My money is on the TCM if you have one. From the reading and researching I've done and my own experience they are often the cause. Of course my method requires you to have several days to have the truck down.