2003 Tahoe Battery drain - alternator working

[Nickpohlaandp]

Hello all. This is my first post in this forum. Real quick about me, I love GM vehicles, I have an '09 Silverado, wife drives a '10 Traverse, I have a '27 Model T Sedan that I'm in the process of turning into a LS powered rat rod, and I just came into possession of an '03 Tahoe (5.3, loaded, leather, Bose stereo, etc.) for $1k. The Tahoe runs and drives great but it has a draw draining the battery. Initially I didn't care because I had just planned on using its powertrain for my Model T, but now my wife wants me to let our son drive it. I'm fine with that, I can get another LS engine anywhere. However, this now leaves me with the electrical draw issue.

I'm planning on using my multimeter hooked up in series with the negative battery terminal and pulling fuses until the draw goes away in order to locate the circuit. However, this leaves me with two issues. First, the Tahoe doesn't have a "door open" button that I can tell, so how do I make the truck think the drivers door is closed while I'm pulling fuses from the panel on the left side of the dash?

Second, after Googling this issue, I've seen a lot of stuff come up regarding the BCM. If I don't pinpoint the issue by pulling fuses and it ends up being the BCM, what am I looking at in the way of hurdles when it comes to replacing that? I found BCM's for around $150-$200, but once I get one, do I need to have it programmed by a dealer, or is that something I could order pre-programmed?

Thank you all for your insight and assistance. I look forward to your replies.

 

[David Paul]

The first fuse I'd pull would be the one for the interior lights controlled by the door. If the draw is gone completely you know that's the problem circuit. If not, then you can check each fuse knowing the lights aren't the draw.

 

[Nickpohlaandp]

So I went ahead and found the draw. Long story short, it's in the stereo circuit. It's got the Bose stereo system, and I'm pretty sure the trucks that came with that had extra amplifiers and more stuff to go wrong. The gremlin is in there.

Here's what I found. Once I finally got my multimeter to work (internal 10A fuse was blown so chalk up one trip to the auto parts store), I hooked it up in series with the negative battery cable to the battery terminal. With the ignition off and all doors closed, I was showing a 2.75A draw. I started pulling fuses and if the draw didn't go away, fuse went back in. When I pulled the stereo fuse the draw dropped to 0.03A. That's an acceptable draw for a sitting vehicle IMO. So I was happy to find that, but just out of curiosity, I pulled one lead out of the multimeter to open the circuit, then plugged the lead back in. This resulted in a 0.75A draw for about 15-20 seconds, then it would drop down to 0.03A. I started pulling fuses again, resetting the circuit whenever the draw would drop down to 0.03A. When I got to the IPC/DIC fuse, the draw was gone.

So in conclusion what I learned is... A. The stereo system is screwed up somewhere. I'm trying to muster up the energy to care, but it's hard to do. B. There's something in the instrument panel circuit that pulls a small amount of amperage when it is first connected to power, like a test mode or something, but after a few seconds, no more issues.

Throughout this whole ordeal I was also able to determine that the A/C compressor is messed up, it makes a horrible noise when trying to engage. This is remedied by simply turning the A/C off. At the end of the day it looks to me like I'm going to get to keep my Tahoe drivetrain for my Model T Sedan Rat Rod build and my stepson can continue driving the 1994 Toyota pickup that I so generously bought him. I'm not sure where it derailed, but somewhere along the line it seems as though he came to the conclusion he was "entitled" to a newer vehicle, for nothing else other than the fact that he graces his mother and I with his presence, eats our food, and sleeps in our house. Now I can tell him with confidence, "Sure, you can have the Tahoe, but you're going to need an A/C compressor, you'll have no stereo, and you're still going to need to check the oil when you fill up with gas because it has a rear main drip just like the Toyota. Oh, that, and you have to pay for all of it." I'm thinking he'll probably end up continuing to drive the Toyota.

Thanks for pointing me in the right direction guys. This is a perfect example of why I love these forums!