The Battery Drain Saga of 2019

[Stillife]

OK so I've been shaking out the issues on a 01 740il for the past few months. I have always had a drain problem. First I replaced the battery with a decent German battery. Still couldn't make it 3-4 days without finding the battery near 6v. Alternator was replaced 2 years prior to me owning it so I don't think that's it. Plus charging the battery was never the issue.

At this time I had also been dealing with the dreaded tree lights. ABS, Brake, and DSC would spark up randomly and throw a Trans Prog Message randomly as well. However trans didn't go into limp mode, no shifting change. I got a used ABS module and had the dealership code it for me. ABS and BRAKE codes/lights went away but DSC never would clear. DSC button is unresponsive and no traction control.

Weird. Trans Prog would still pop randomly as well. Still no limp mode. Still had the battery drain. So I grab my multi-meter and set up in the trunk. After triggering the latch and waiting 16min the draw is fluctuating 0.5 -2 amps and I can hear the Nav DVD spooling and crunching and quietly beeping. Eject button is unresponsive and I watched it for 30 min and the Nav DVD is just freaking out the whole time. Holy crap did I just find my electricity demon? At this point I'm just glad to have a bad part to blame and not some elusive wet/corroded connector deep in the depths of interior trim.

Question time.

Can I just unplug this relic and lose just Nav? Or will it brick the whole radio / CD / DSP system? Frankly I don't care about the built in GPS.

If I need a replacement then what are my options compatibility wise? I believe I have an MK4. Do I have to code it like the ABS Module or is it plug and play?

[SilverIris]

Try pulling its fuse (F69, 30A ATO style fuse) on the other side of the trunk and repeating the parasitic draw test. Usually, navigation drives go to sleep after a minute. E38s were given the MkIII system from the factory, which was CD-based. IIRC, retrofitting a MkIV (DVD-based) is a plug and play swap with no coding needed.

[Stillife]

Try pulling its fuse (F69, 30A ATO style fuse) on the other side of the trunk and repeating the parasitic draw test. Usually, navigation drives go to sleep after a minute. E38s were given the MkIII system from the factory, which was CD-based. IIRC, retrofitting a MkIV (DVD-based) is a plug and play swap with no coding needed.

I checked and I have the MKIV with DVD but weirdly no widescreen display. Can I replace it with any MKIV from E39 E46 X5? Or can I just pull it and keep my stereo?

[White94RX]

Why not just try it and see? Just unplug the NAV unit and see what happens? You're not going to do any permanent damage.

Man, we just don't see older cars like that anymore. But come to think of it, isn't the NAV unit basically the head unit (the brain) of the screen, radio, etc? Unplug it and see what works and what doesn't.

[SilverIris]

I checked and I have the MKIV with DVD but weirdly no widescreen display. Can I replace it with any MKIV from E39 E46 X5? Or can I just pull it and keep my stereo?

I don't see why it wouldn't work. If you find another working MkIV nav unit from a salvage yard, let me know. Marina wants one...

[Stillife]

Why not just try it and see? Just unplug the NAV unit and see what happens? You're not going to do any permanent damage.

Man, we just don't see older cars like that anymore. But come to think of it, isn't the NAV unit basically the head unit (the brain) of the screen, radio, etc? Unplug it and see what works and what doesn't.

OK guys I went ahead and pulled Fuse 69 and lost all radio functionality and CD playback. Reinstalled fuse and pulled Nav DVD unit. Car now draws .04Amps after 16min timeout. So I guess that confirms it. I started it up without Nav installed and my display has no power but radio and all associated button functions work.

Soooo I guess it's time for a new MK4 unit. Salvage yards are pretty crap around here. I got lucky with an MSport wheel and diff last month but I want proof of function before I buy a $400 used part. Any sources?

[Mayorchuck]

I checked and I have the MKIV with DVD but weirdly no widescreen display. Can I replace it with any MKIV from E39 E46 X5? Or can I just pull it and keep my stereo?

Yes. Same unit. There is a 2001 part out thread in the forum here. Might see what he has.