I have a 2003 trailblazer. Battery is only 4 months old. Went to start it and it was dead this am. Hooked up the jumper cables and it started right up. Took it to the auto supply for testing. Everything checked out so drive it to work. Started just fine and came home. Went to lock it and the security light started blinking and would not shut off. Tried manually locking with the door electric lock button. It still did it. I have had this vehicle for 4 years and its just started this. I think is what drained my battery or something. I cant leave my vehicle unlocked all the time but I can't have a dead battery all the time either. Anyone have any ideas what might be going on?

 

Sounds like a trace of the electrical drain is necessary. A good place to start is by pulling fuses while monitoring the current flow through the battery.

It is not as accurate but there are tables that will allow you to measure the voltage drop across a fuse and then convert the voltage drop into the amount of current flowing through that fuse. You need a table because the conversion is different for each fuse. (It is just Ohm's Law but the table makes it easier).