Hi guys -

So I have been continuously destroying my battery for about a month now. I have a car computer and other various mods and additions, which obviously would be the first places to check.

Mods and additions:
Matrix 10 Car Alarm System
Car Computer (Computer in back, LCD screen in front, all run off of the car computer power supply, an M2-ATX. In other words, the LCD isnt getting any power unless the computer is getting power and turned on).
Planet Audio Multichannel amp

Interior lighting switched to LEDs
HVAC LED mod to white and blue LEDs
Guages LED modded to white and blue LEDs

and thats it.

I take the fuse out for the computer, overnight the car dies. Not the computer.

I take the main power fuse out for the amp and the computer, overnight the car dies. Not any of my audio setup. The computer only connects to a few things: a USB GPS dongle, the amplifier, the LCD up front, and a USB hub that leads up front. With the computer fuse out, everything dies. With the main fuse out, amplifier and computer and all accessories die.

At this point I decide to start measuring current flow in the fuse box. I figured I was looking for 100mA or more through one fuse, and I found it.

The ECU-B fuse is pulling varying amounts of current (here is where it gets tricky).

I measured the current to be about 190mA. I then removed the HVAC unit (parts of which I found to be connected to the ECU-B fuse via the tC 2005-2006 wiring diagram from this forum), and measured again. only about 45mA. I had found my culprit!

I completely redid my LED mod on the HVAC, and came back and decided to test again. Without the unit even in yet, it appeared to measure about 40mA. Then sometimes 180mA. Without changing anything in the car at all, the current had tripled for seemingly no reason.

I removed the gauge cluster to see if that had an impact. However, my current measurements were still just as random. always either 180mA down to 45mA and sometimes less, with seemingly no correlation to what I was doing in the car. I am obviously looking at everything that I have done/added to this car before anything else, but am stumped at this point.

From the wiring manual, I can see that the ECU-B fuse connects to:
ABS, Tire Pressure Warning
Air Conditioning
Back Door Opener
Combinational Meter (Gauge Cluster)
Cruise Control
Door Lock Control
ECT
Engine Control
Engine Immobilization
Illumination
Key Reminder
Light Reminder
Power Windows
Seat Belts
Sliding Roof
Wireless Door locks

A lot of this appears to be contained in the guage cluster and the HVAC unit. I remove both of them and the problem persists.
To say the least, THIS IS A LOT OF STUFF TO LOOK THROUGH.

So to cut to the chase, my question is, has anyone had this problem before?

(longshot question) Can anyone think off the top of their heads a part that may intermittently draw on the order of 180mA for no apparent reason? I have checked so much of my wiring and can't find anything!

I have a question for you... if it's only 180 mA, how is that draining your battery overnight? That's an extremely small amount of power. Maybe I'm wrong... But, I guess to answer your question... I read somewhere in the manual that there's something that tests the fuel or the fumes in the fuel tank about 5 hours after you turn your car off. It mentioned if you heard somwething, that's what it was.... but Other than that idea, I have no clue.

it didnt drain my battery overnight, sorry if I said that. It drained it over 2 days, which isn't that unreasonable at all. 200mA is certainly significant when the car is off.

I thought it was the guage cluster:

Put the gauge cluster in, draws about 200mA
Take the gauge cluster out, draws a little under 10mA.

I happen to have a spare gauge cluster which I know works, so I put that in just to make sure it's the gauge cluster.
It draws 200mA through the ECU-B fuse still.

This leads me to believe its something connected to the gauge cluster but not the cluster itself.

In 48 hours that accounts for 9.6amp hours of a 50+ amp hour battery charge so you have something else going on there. Did you have the door open to the car when making these measurements? Key in the ignition? Better put your amp meter between the battery post and the terminal clamped to it and then remove the clamp from the post and measure the current flowing - this keeps the ECU and everything powered up - then put the terminal back on the post after you get a reading.

In 48 hours that accounts for 9.6amp hours of a 50+ amp hour battery charge so you have something else going on there. Did you have the door open to the car when making these measurements? Key in the ignition? Better put your amp meter between the battery post and the terminal clamped to it and then remove the clamp from the post and measure the current flowing - this keeps the ECU and everything powered up - then put the terminal back on the post after you get a reading.

It's not something else going on. No, the lights werent on and the door wasnt open.

It killed my car in 48 hours, I know that much.
I recharged my battery. Then, I went hunting in the fuse box and found that the ECU-B fuse was drawing a much larger amount of current than other fuses.

(Note: My ammeter has a 200mA limit. However, if the 200mA limit is surpassed, the meter (interestingly enough) does not blow a fuse, it simply beeps. In the testing I've done, the meter will beep for a bit and then I see the current fall to about 190mA. This might suggest a current limiting circuit as protection in the meter, so I'm not sure if the current is larger than 200mA without the ammeter in).

Anyway, so I find that the ECU-B fuse is the 'culprit' persay. I fully charge the car battery, I remove the ECU-B fuse, and I go away on vacation for a week. I come back, the battery is unscathed.

Today I started pulling harnesses in the Instrument Panel below the drivers side section, but didnt really find much conclusive. With the gauge cluster in, troublesome amounts of current flow through the ECU-B fuse. With the gauge cluster out, current measurements seem fine to me. As mentioned up a few posts, I tried another gauge cluster in the car, which produced the same results. The problem must be something hooked up to the gauge cluster but not the cluster itself.

If the battery charged back up fast then you have a shot battery otherwise you have about a 1 amp drain someplace for it to kill the battery in 48 hours. To really test the car out you need a higher amp scale on your meter. Now I have a ScangaugeII connected to my xB and I find that if I use the remote lock the ECU wakes up and activates the Scangauge and usually crashes it so bad that I have to unplug it to reset the Scangauge. Alarm systems also draw a little bit of power.