Drawing battary juice even when the key is off

I see this a lot. Sometimes it causes the battery to run low on charge and then the alarm will go off and the lights will flash. Anyway it causes the battery life to diminish in less time than it should. One cause of this can be a dirty battery where voltage is going accross the top of the battery between terminals. You can actually check or read how much voltage is moving by using a voltmeter and putting the negative on the negative and the positive in the middle of the termianls. Never use coke to clean a battery. Use baking soda and water. Another common cause of this on 1998 - 2000 Yokons is the positive battery wire connection to the fuse block. This is located by following the positive wire from the battery to the point it intersects with the block. At that point, take everything loose and clean it with a wire brush and reassemble. Make sure you disconnect the negative battery terminal first. Even if it looks some what clean, clean it. The grounding there can cause the parasitic draw your experiencing. It would be a good idea to get the alternator checked out at your local parts store. If the alternator isn't charging the battery enough, the battery sits with a low charge. The battery is still keeping some systems awake like the alarm system. Make sure when you close all the doors that all interior lights go off. Some Yukon customers have thier vehicles die at traffic lights because the alternators in those vehicles don't last as long because of all the bells and whistles the vehicles have. I would recommend putting in an original equipment alternator if it is needed. Especially in that vehicle. If none of this helps you will want to check you grounding and clean any corrosion. This is easy. Just go under the vehicle and look where grounds attach to the body. Take it apart, clean it to the bare metal, put it together and spray a sealer over it so it doesn't rust. Some GM products have bad grounding studs and you have to replace them. I like using ether a M6 stud and nut or a M6 nut and bolt or a M8 nut and bolt. Which one to use depends on where it is being placed. Once you see where it is needed you can look at the stud combinations and choose the right one. If none of this helps I have herd of GM radios causing a whining in the alternator but I haven't herd of a link to that making the alternator fail. Good luck.

Check for a dirty battery, to start with. Dirt/grease is a conductor of electricity. Second, there is SOME draw for the computer memory, clocks, etc. Make sure all interior lights are off. If you have any aftermarket installations, the problem could be a positive wire shorting somewhere, though that should blow a fuse.