I have a 2004 z71 chevy tahoe 4x4, 5.3L, with 28,000 miles. I reolaced my factory battery back in April after I had to jumpstart it on 3 different occassions. I don't drive it much so I just figured it was time for another one. Bought a new battery and same thing. Battery dies every 7 to 10 days if I don't drive truck. I have had several people look at this since and they all give me a different answer. Since all of this I have installed a new radio in my truck. Nothing special, and I am still using the stock amplifier so no new power gain, besides problem started before radio install. Dealership says the radio is causing this and it took them probally all of 30 minutes in shop total. I took to radio installer twice and everything is hooked up correctly. I took to a local starter, alternator, battery specialist and he said with the truck off I was pulling 8 and a half volts. He said my alternator was charging fine and we replaced the battery I bought back in April because it was shot. Ok so he pulled every fuse under my hood and inside vehicle and charge was still there. I even unhooked new radio completely just to show him that I did not think it was the radio. He agreed that it definately was not the radio to. I am taking truck back to dealer to look at again. I was wondering if you had any suggestions on where to start at? I keep getting the run around. A mechanic told me that it could be the alternator or starter having a internal problem.
You need to have your computer software (firmware) updated. My '04 Tahoe did the exact same thing, starting the first time I brought it home. The battery was so flat after 3-4 days of not being driven that it appeared to be totally disconnected. I suspected a computer problem because the OnStar status light would go red and, if I didn't drive the truck regularly after that, the battery would die. Pulling and replacing the OnStar fuse would reset the status light and everything would be OK. I would have left the fuse out (I don't care about OnStar) but it also feeds the DVD player. After 2-3 battery death episodes, I took the truck to the dealer and asked them to update all the firmware to the latest revision. The OnStar light almost never goes red now (I don't have service but it worked normally the rest of the free trial) and I haven't had the battery death problem since. The dealership denied this could have fixed the problem but the facts don't lie. Something was sticking on and draining the battery. You should also have your battery load tested as it may have been weakened by the deep discharge cycles.