i own a 99 yukon slt. i have had it for about 4 years now. it has always had a battery over nite draining issue.i have put sevaral new batterys in it. and they dont lst long if i dont unhook the battery.everything works and no interior lights stay on.no underhood light problem.no hung relays. no noises after key turned off. when u take the battery cable loose and brush against the batt terminal wow what a spark.i know it should have a slight spark becuase of computer and radio and so on memeory issues.this is different i took the computer all the way out of the truck and it still jumps enuff spark to set off a stick of dynomite.under the hood i have taken all the relays out of the relay fuse block. i have three 50 { even if they are put in one at a time} amp fuses that will let the battery create this extreme battery spark issue.i can put all others in and leave 3 them out and i no longer get this huge spark. if i can find out what is on these 3 circuits then i should be able to find the culprit or culprits.how can i find out what these 3 circuits supply juice to? last i have tried to include all info i can not just to fill up space. in hopes this is something familar to someone. p.s. i have seen on another site that the body control modual has had an issue like this on trucks like mine. ok! where is it located i am having trouble finding it. i have a 99 villager ripped up in the drive way right now. my wife needs to be able to have a dependable way to work so i am trying to fix to different vehicals at once.:screwy: this is me! help and thanks!!!!!!!!!!!

Sometimes the owners manual will tell you what the fuses and relays do. If no manual is available, its time for some trial and error

Put the battery in and put in all fuses and relays except for these 3 50-amp fuses and start trying all the circuits, switches etc to see what does not work.

In my experience, the only fuse-protected circuit that can create such large draw (without obviously doing something) is the starter motor relay (or solenoid) or the ignition circuit.

ok ! buy the way i did replace alternater also thinking diode problem but that was not it.starter motor relay or ignition circuit. gottcha and put all back in {except those three} see what works duh why didnt i think of that? :loser: ok when she gets home well give'er another go. how about under the dash arent there any relays under there?

Did you have any luck finding the cause of your problem? I have a 99 Yukon SLT and am having the exact same problem. I have had it thoroughly tested...no problems to be found, no parasitic draws, but it still happens on occasion. I noticed yesterday when the CD player is on I can hear a zinging noise through the speakers. It increases with the RPM's. Please let me know if you found your problem, this is about to drive me nuts.

Did you have any luck finding the cause of your problem? I have a 99 Yukon SLT and am having the exact same problem. I have had it thoroughly tested...no problems to be found, no parasitic draws, but it still happens on occasion. I noticed yesterday when the CD player is on I can hear a zinging noise through the speakers. It increases with the RPM's. Please let me know if you found your problem, this is about to drive me nuts.
havent been here in so long.hope this makes it!hi! no i have not had any luck.mine does have a parasitic draw but it comes and goes!the truck is sos bad now i have ruined the 2 batterys that are in there now,why you might ask? well the battreys are weak form constant full charge then drained to dead battery! when u get a fast charge on a battery it caues plate deterioration.so the reserve battery life just gets shorter and shorter.i i ahd to install a quick dissconect under the hood.when we get out of it i raise the hood and pull my quick clip cables and kills all battery power to the truck.now its gotten so bad if u dont unhook the power just going inside to wallmart for 30 mins the batterys are dead when when we come out.then some days or some weeks we will forgetto kill all main power it may go 2 3 4days and not have an incident. new problem.my day time running lights dont work anymore,go figuer! i am an ex mechanic and one of my specialtys was finding dead draws such as this but i have had no luck! i had another post somewhere, i cant remember where!he has the same exact issue as we do same year same model. someone told him it was the body control module.i never heard any more from the guy! i cant find the body control module.everone says its in the center console but i found out thats just in the yukon denalli! to make a long story short they want 70 bucks an hour to try and run it down.i dont have it and i never will have that kind of money.and i dont even have the crappy cd player in the truck anymore.i am looking for a master switch i can mount in the fender so i can cut power without having to open the hood.well thats what i found theres somemore info on the subject.we arent alone in the quest to fix this issue i found atleast 4 other people with almost identical issues!if u find out where the body control modual is ,drop me a line please. any other questions or ideas let me know! bob at smsrobertks@live.com .good luck!