Strange Electrical Problem

Hi all!

I've been having a hard time diagnosing an issue with our 99 Yukon. A few months ago I was going 65 down the interstate and it straight shut off on me. I pulled into the shoulder, put it in park, took the key out, then tried to restart it. No clicking, no turning, nothing. We had it towed back to the house and I started going through everything ignition wise. The battery was dead, but recharged fine. I replaced just about everything except the alternator and starter which tested fine at Auto Zone. So new ignition switch, module and coil, spark plugs, wires, cap and rotor, the works. The rotor was worn pretty bad and miraculously after replacing that, the Yukon ran, though it was rough. It would shake like it was missing during idle and sure enough pulled a code for cylinder 2 misfiring. Then, the missing stopped. For about 2 weeks it ran fantastic.

Now, I was trying to back out of the driveway and it died again. Straight shut off. I put it in park, took the key out, tried to start it up again and I got clicking, the radio turning on and off and an array of strange clicking noises coming from the steering column. The next time I keyed over I got absolutely nothing. The third time, it started and I was able to pull back in the driveway completely. I shut it off and came back to it later to find the battery completely drained.

I've got the battery recharging now, but I'm completely at a loss. I don't even know where to begin. I pulled all the fuses out and they LOOKED fine but I was told the best place to start is to take a test light to each one to find which system is faulty. Is it possible this could be the computer?

Has anyone had a similar problem or have any idea what could possibly be going on?

Thanks for any and all help!!!

well the question you shuold ask your self is:....... With this problem i have (battery going dead) how many things can kill the battery / power. Hint there are only a few things that can do this. Put on you thinking cap and check it out.

So the 6 month old battery ate the dust, like the 2 before it. Replaced the battery and hooked up a multimeter. Apparently, there is no parasitic draw on the battery when the car is at rest. And the alternator is fine. I'm at a loss.

Have you checked the voltage with it running to verify that it is charging ?

Have you hooked a test light up to it ?

Went out and bought a new multimeter, repeated the test.

Turns out my old multi died. Oh, technology. Thanks for bearing with me there.

So the new and WORKING multimeter reads that about 4.5A are being pulled from the battery when the car is at rest. Holy cow. That explains a lot.

There are four different fuses that when pulled one at a time, drop the reading down to 2.1A. For some reason though, the car never shows less than 2.1A. And this is with all the doors closed (or the door sensor clamped into the "shut" position).

Under the hood, the 50A Lighting (Headlamp and Panel Dimmer Switch, Fog and Courtesy Fuses), 50A Battery (Battery, Fuse Block Busbar) and 20A Horn (Horn, Underhood Lamps) fuses. The underhood light DID remain on during the testing so I wasn't surprised to see that one catch, but it dropped significantly for being one little bulb.

Inside the door panel, the 20A Courtesy Lamp (Courtesy Lamps, Cargo Lamp, Glove Box Lamp, Dome/Reading Lamps, Vanity Mirrors, Power Mirrors) fuse.

There is an obvious trend with LIGHTS. Which is ironic because I have never seen any lights remain on after the vehicle is shut off. You would think that if a light was remaining on it would be a little obvious.

I'm also confused because there are FOUR fuses in question, and even with those four out, the battery is still being drained 2.1A. From the wonderful instructional video I watched to learn how to do this, it was said the car should only be pulling about 50mA. What could possibly be drawing ALL that power?!

http://www.youtube.com/watch?v=KF1gijj03_0&feature=related

Trying to make my way through some wiring diagrams now to find a common denominator. Does anyone have any suggestions? Thanks in advance!