2002 Suburban - intermittant starting problem - please help!

[c921203]

We have a 2002 Chevy Suburban and only drive it on the weekends - if not every other week. Occasionally we go to start it and it's dead. We've brought it into the shop numerous times but the problem cannot be recreated... Our battery and load are perfect, in fact, we've even replaced several times, our alternator is fine, nothing is showing up when it's hooked to the computer diagnostics, but we still continue to have this problem. Has anyone else had similar issues and/or what did you do to fix? I had a non-Chevy shop owner look at it and he thinks it could possibly be the timer (which is part of the BCM?) or something to do with Onstar trying to get in touch with the vehicle - whether or not we subscribe or not? (i.e. draws the batter intermittantly - sometimes we go to start it when we need to use it and it works, sometimes it doesn't!) UGH! Please help - we're spending a LOT of $$ trying to figure this out! Thanks in advance!!

[gmtech79]

How long do you drive it when you do take it out? How many accessories do you have running when you use it? Do you leave the key in the ignition when it is parked?
Yes it could be the BCM waking up or not going to sleep. Or for that fact any module can wake up at anytime causing this symptom. There are alot of known issues with the onstar VCIM or VCU/VIU (depending on onstar generation, you should have a VCU/VIU) not operating as designed and causing phantom parasitic draws. you need to let the vehicle sit with an ammeter in min/max mode overnight or longer and see what your peak current draw is and what your average current draw is. You dont want to see anything over 25 mA, preferrably no more than 20 mA. Post your ratings of the battery that you have in the vehicle, CA, CCA, and reserve capacity.