OnStar Backup Battery 2004 H2

[Olfart]

Originally Posted by Easy Ed

Cannot find anything about a battery for OnStar in the 2003 service manual

I can't either. but I read somewhere that GM started putting in backup batteries in 2006. My truck is a 2004, but in 2007 GM replaced my OnStar inder warranty to change me over from analog to digital cell phone system. So more than likely my OnStar system is now a 2007 with a backup battery which is used to keep OnStar alive after the 48 hour main power automatic shutoff of power from the Hummer battery to keep the main battery from running down. As long as I run the truck every day it's OK, but if it sits for a couple of days I get the red light on OnStar. Once I have the truck running I can press the OnStar button and the light will go white again and it works OK. I imagine that with a bad backup battery the features like antitheft GPS and remote unlocking won't work if truck is parked for more than 48 hours.
Guess I'll have to give my GM dealer a call, but I hate to hear their cash register going KACHING.