Battery Drain 2008 Chev

[Wagtail]

A wee bit of an update on my battery drain fault... the battery maintainer wasn't really keeping up.

When I took the ute in for its annual service I mentioned the drain. They tracked it down to a superfluous (yeah, I know, big word) toggle switch that the previous owner had 'something' hooked up to. They disconnected the switch and the battery's stayed charged ever since. :thumbsup:

Now that I'm heading into winter, I'll see if it holds true. So far, so good.

 

[Xfaxman]

Just a (very) late followup on this. I paid to reactivate the OnStar and immediately all the battery problems went away. Still working good months later. Hope nothing happens when I transfer the XM satellite radio subscription to my new car next week.

I guess I can say I paid the money for OnStar instead of to the dealer for diagnosis! Maybe that's how they hold you captive!:laughing:

Now that is a horrible thought. I was going to let my OnStar lapse

That's when the Onstar crap would be ripped out and tossed into the trash can. --------------------------

There is a fuse you can pull to keep Onstar from calling home to see if it needs to unlock the doors for dummies like me that locked the keys in the truck. :thumbsup:

 

[dickfoster]

Re: Battery Drain 2008 Chev--Solved??

OK, problem is located but not fixed. Appears the malfunction is with the Sirius/XM radio and/or OnStar system. When I pulled the radio fuse current dropped much lower, maybe around 1 amp or less. Hard for me to tell exactly as I only have an analog ammeter. I also pulled the DIC fuse which supposedly also powers the OnStar. I was hoping for a simple problem like alternator, but apparently no luck.

These things are very hard to pinpoint without the right equipment and/or a lot of time. The diffferent modules (PCMs, BCMs, etc) continue to draw power even after you turn the key off. And then they will restart/reset after you disconnect the battery cable when you put the ammeter into the circuit. You have to get the ammeter in before you break the circuit, ie. you have to parallel the ammeter with a switch so that you never lose power to the modules. Some of the modules can require several hours to power down completely and go to "sleep". And then, even after they power down they can start up again, either by design or due to malfunction. Like OnStar, which will try to "call home" with your diagnostic report. This is all way too complex. Or the radio is designed to continue to play after you turn the key off until you open the door or a certain amount of time passes.
If you have the Verizon calling option with the OnStar it has to switch the speakers to the phone unit and silence the radio. It may be just a coincidence, but my battery trouble started right after I let the OnStar subscription lapse a month or so ago; who knows?

So now I'm completely frustrated and annoyed. I'm paying for a sat radio subscription but I can't leave the radio fuse in overnight. I was considering starting the OnStar up again, but now I'm thinking why bother.

Sorry this has been so long-winded but I feel I spent a lot of time on this and still no real solution.

I found and old TSB from back in June 2009 and they have you performing what seems like hours of testing with DVM and osciliscopes and then either reprograming the ECM or replacing the XM module. And this is only for the radio, similar things can happen with power memory seats, dual zone HVAC, fuel pumps, lift gates, etc, etc. I'll keep looking for more up-to-date repair documents.

How is the average guy supposed to fix something like this at reasonable cost? Have these systems gotten more reliable in the past 8-10 years, I hope so? Maybe those were lean times for GM designers back then?

The radio should be on a switched (key on only or the accessory circuit which also should be off when the key switch is off). Maybe that's your real problem. Things are on when they should be off, so look for a relay somewhere that controls this. You should be able to locate a wiring diagram for your vehicle on line somewhere.

BTW with the key off, parasitic current drain should drop down into the milliamps due to the ECU, Clock and stuff like that. If it's a whole amp then even that much is still a problem but maybe it's the key on/off relay thing so the accessory buss is still powered up with the key off.

 

[dickfoster]

There is a fuse you can pull to keep Onstar from calling home to see if it needs to unlock the doors for dummies like me that locked the keys in the truck. :thumbsup:

Heck everyone knows that's what they make wire coat hangers for.