Need some help, my battery is draining :(
 

When I am not driving the car in 3-4 days, the battery is dead, I have to start the car with a booster, then it starts like normal. Checked the dynamo, it works fine, got a brand new ACDelco battery 3 weeks ago, it still drains. I got a message in display last week - "service air suspension", but only once, then it dissapeared. Its a 2003 model. Does anybody have some thougts on what the problem might be? It is sooo frustrating. I appreciate ALL answers and tips. Greetings from Norway!

Remove or disconnect the Onstar junk that is useless and non-functional for one....

Thanks for reply! Okey, so Onstar unit are known to cause drain? I will disconnect it, worth trying!

Yes. Especially the older analog ones that cannot even be used anymore. Just pull the VCIM (Vehicle Communications Interface Module) fuse from the fusebox under the hood. That kills the power to the onstar system.

Next step would be to start testing for parasitic drain. Few ways to go about that and a few things to be aware of. Search online for how to test for that. Main thing to be aware of is on the H2 (and many other GM vehicles) after you shut it off the BCM and climate modules do stay active for a few hours. They do not draw much and not enough to kill the battery in 3 days though. But if you are using a clamp meter or something to check for amperage draw you will get some readings from those for a few hours after you shut the truck off.

Thanks for a very helpful answer, MixManSC! Now I know what to do, will be trying it out after work.

As always Mixman is spot on with his suggestions. I will add that I had the same issue on my '03 and it was the electrical portion of the ignition switch. It would not shut off all the way and it was acting like you left the key on. Replaced the switch and all was well.

have you installed any after market unit, such as rearview camera or light bars? poor connection might drain battery.

I had this same issue and it was my aftermarket dvd headrests. They had apparently been wired into the cigarette lighters so they were always draining power even with the truck off. I installed a switch to turn the dvd screens on and off, battery has never died since. As they mentioned, you can also try pulling the Onstar fuse. If Onstar doesn't get a connection, it will continually try to attempt which can result in a drained battery. I had tried this and it didn't fix my issue; it ended up being the rear dvd screens

@mixmansc ... Thats a good shoot . I hate onstar so much I get rid of it without any reason . But now wondering if tha was what caused my batt to drain a few times

Very well could have been. Removing or disconnecting its brain has the same affect as pulling the fuse.