Had this truck about 6 months 7600 miles. No problems at all until I ran over something on the road and it knocked the DEF module and wiring off the frame. This was fixed, however ever since getting this repaired if the truck sits for 2 days on day two it will not start.
Took to dealer they charged batteries and eluded that perhaps my GPS was draining it down. Left everything unplugged and sure enough 2 days later it would not start. Jumped the truck off and ran for about 2 hours, the follwoing day I started the truck turned it off no problems but the following day again it would not start. Took to dealer again and after two days and parasitic drain checks there's no problem. Dealer says after everything sleeps the current draw is about 24mA which is undere 30mA spec.There must be something wrong. I've had my GPS plugged in and the truck started fine after sitting a week. Now with nothing plugged in it won't start after two days.. but dealer cannot find anything wrong. Ideas???

 

Sounds to me like there's something wrong with the dealer. Are there other dealers in your area?

 

Maybe. They have good reputation I'm picking the truck up today if I have the problem again I will try another dealer.

 

In defense of the GPS theory, I have had a near run down with my 07 Tahoe's battery that turned out to be the GPS, the battery in my Garmin has gone south and will not hold a change, however leaving it plugged in it will continue to try and charge indicated by the warmth on the back of the unit... warmth translates into power useage and battery drain... its like running a small heater !

 

Hopefully good news. Let us know!

 

I have a dash cam that stays on 24/7, and it gets warm to the touch. I can let the truck sit for 3 days in the cold and I have never had a problem with it draining too much power.

 

Got the truck back yesterday. Dealer said they did implement a tsb but found nothing wrong. The really strange think is until recently I always left my stuff plugged in off but plugged in. For 6 months there was never an issue then all of a sudden the battery started going dead. Since then it went dead three times with nothing plugged in. Dealer ran parasitic test says draw is under 30mA minimum and has found nothing wrong. It's been colder out but I garage it and it went dead all those times while in garage. Have not tried it yet today I hope the issue is solved but since dealer finds nothing I don't have a warm and fuzzy.

 

when you garage park it, are you removing the key from the ignition cylinder?

Even off, the presence of the key in the cylinder will keep some modules from going into a sleep state. This will create a larger parasitic draw that the dealer wouldn't see as they would test with key removed.

Any aftermarket stuff on the truck, running lights, remote start etc

 

Thanks everyone keep the ideas coming. I do pull my keys out every time I park the truck. As you all know I got the truck back Friday. Yesterday morning the truck cranked but I noticed the battery gauge seemed a little low, 3 hours later I tried to leave the house only once again the truck would not crank low battery again. The only thing plugged into thus truck is all features of the truck. I have nothing if mine plugged in to draw any power.
Finally had enough I called Chevrolet and I'm waiting on a call back from district repair team should get call tomorrow.

 

You could also try pulling a few select fuses and relays to see if you can narrow it down....
Might also try just disconnecting the battery itself to see if it runs down on its own...