2008 Tahoe dead battery
 

My friend who I travel with a lot has having problems with his 2008 Tahoe battery going dead. This is the third time in 30 days that the Tahoe has been towed to the dealership. They replaced the battery the first time, it went dead a week later, they then replaced the BCM, 10 days later the battery is dead again and they say they can find nothing wrong with the vehicle. The dealer states they have heard of this problem before and don't know what to do. It is currently at the dealer over the weekend to see if the battery is dead on monday. The dealer seems to think the computer is turning something on and draining the battery. The Tahoe does not have a nav system in it if that makes a difference. Anybody else have this problem or know what is draining the battery?
Thanks

Well...I believe the Body Contol Module is the "computer" in this case. BCM's had an issue back in 2007 leaving some of the components powered up, and their load was amazingly high; enough to drain the battery within several hours. The issue was fixed with recall 07033 which involved a reflash of the BCM. I had this problem with my 2007, and the reflash cured my battery rundown problem. The problem with a traditional flooded cell starting battery is if you bring them down below 10.5V their charge cycle is drastically reduced. Basically, its life is reduced. If this incident had happened a number of times, the battery is shot. The system load on the battery can be easily monitored, and dealer shouldn't have to leave it in the garage for the weekend.

All that said, I would think the replacement BCM would have the latest firmware loaded. It should be something to check though.

Update: Tahoe had dead battery at dealer after sitting over weekend in their service area. That was a good thing so they know he is not nuts! This afternoon all dealer would say is "it is in the shop and we are working on it". Not a clue what they suspect from them.

If I leave my 2003 Suburban overnight with the Garmin GPS on the battery is virtually dead in the morning. Hard to believe that the slight drain by an electronic device would be enough to drain the battery...and the battery is a year or two old.

I leave my Garmin on in my 07 and have had no issues, how old is the battery?

Dick_B: Welcome to the forum.

Have you tried leaving overnite w/ the Garmin unplugged? Also might get battery and charging system checked. Most auto parts stores will do it for free.

Had a simlar problem with my 97 tahoe. Turns out it was the courtesy light under the hood staying on, even with the hood shut. I wasted 3 batteries before I found the problem.

That is a good point that sometimes good way to troubleshoot something like a run down issue is to park the vehicle in a close garage and turn off all lights, let your eyes adjust and look for light leakage...
Another good one is vanity mirror lights,glove box and any console lighting ,they can be on an you would never know it except for the dead battery... I found this to be the issue on my ex-wifes 99 Tahoe.

07's and up should have a run down protection feature that turns off most power after about 10min... I accidental left open (didn't close all the way) my rear access glass, a coworker came and told me a light was on in my vehicle and by the time I got out it was already off.

Ghost in my instrument panel
 

My new (to me) 2008 Suburban has had its battery drain twice now (both times when parked for more than a day and a half). I noticed something odd the other day when I was sitting in the driver's seat looking for my cell phone. My keys were not in the ignition.

I would hear a double clicking sound and then would notice that the needles on my tachometer, speedometer (and one or two other gauges) would jump up from the rest position to the zero position. THey would stay there for about 30 seconds, then drop back down to the rest position. At the same time I would hear the dvd player whirring. I ejected the disk from the DVD player (still without putting the keys in the ignition). After this the same two clicks and jumping needles happened. This process recurred every minute.

Is this an ignition switch problem or something else?

When I open a door of my Burb, I can hear the nav system scanning the disc - maybe a preload of the cache? I don't see how it could possibly be enough to drain the battery. My Burb is my extra vehicle - it usually sits 5-6 days out of the week. Never had any battery issues, even when it's sat for a few weeks at a time, even during this past ridiculously cold winter.

I chased charging system problems/recurring dead battery in my wife's minivan. Finally fixed it by replacing both the battery and the alternator at the same time.