2006 X5 3.0i keeps running with key off

[Siggy]

Using my Google Foo, I found some information that suggested it might be the alternator back feeding to the ignition switch. The fix was to install a diode inline to keep that from happening.

That sounds a lot more like what's happening than anything else I've been able to figure out. It's certainly backfeeding at some point. I'm not sure how that would make everything come in when you hook the battery up, but I do think that could be the power issue where it's backfeeding into the ignition switch.

That info was from a non-BMW place so it might not be relevant.

Any thoughts? Or thoughts on what to check next?

I pulled all 3 of the main fuses on top of the fuse box, the 60,50, and 60A ones. All look very clean, don't smell burnt, and all text fine for continuity. The lugs they bolt on all look clean with no obvious signs of issues.

EDIT: My last post on page 9 had additional testing results.

[andrewwynn]

once the alternator is running, i think you can unplug the control lead; you'll for sure get an SES but if the engine shuts off you have your culprit.

there are a bunch of diodes in the alternator and if one fails it could easily send some weird voltages backwards through the control 12v 'ignitor' pin. (which i think BMW may also use for communication but not sure if alternator is 'dumb').

[Siggy]

I hooked everything back up for the most part, I did take the top of the airbox off (where the air filter is located) so I could get access to the plug on the alternator. Started it, it ran, I pulled that quick disconnect 2 wire plug on the alternator and the car immediately shut off. I went and took the key out and the dash lights stayed lit. I took the ignition switch off and measured power on the wires again.

With the plug on the alternator unplugged, the key out of the ignition, the ignition switch unplugged from the harness, I'm getting 1V on 5,6,7 pins of that ignition plug and 10V on all the other plugs.

I had to unplug the battery to get it all to stop.

I feel like I'm in the area or close to it, but still haven't found the issue yet.

[Overboost]

Seems like an unusual problem. Usually that is a ignition switch failure but I see you have eliminated that possibilty.

Being that is not a problem reported by other members through the years, I would start looking at anything installed that is aftermarket like Android conversions. Something is shorting KL30 and KL15 together.

[Clavurion]

Originally Posted by Overboost

Being that is not a problem reported by other members through the years, I would start looking at anything installed that is aftermarket like Android conversions. Something is shorting KL30 and KL15 together.

At this moment after all this test and measurements I can't think of anything other than internally failed junction box (front fuse box) that could cause these symptoms. I've never heard that these on E53 could fail like this. So I would also start digging anything that is not factory fit on the electric system.

[oldskewel]

I have not followed this thread closely, but I commend your perseverence and will offer some comments:

Originally Posted by Siggy

... Started it, it ran, I pulled that quick disconnect 2 wire plug on the alternator and the car immediately shut off...

That is a problem, right? The engine should continue to run when the alternator is disconnected (battery still connected, etc.), right? The engine should be able to start, run, and stop with no drive belt or alternator in the car, right?

If so, then that may be a clue that the alternator is somehow powering something that should actually be controlled by the ignition switch. I.e., the ignition switch should be holding something high, and it's not (I know you're on your 4th switch, so the problem is somewhere outside of that), but rather than just being failed, the alternator happens to also be connected to that point, keeping it high. I'd follow that debugging path.

Originally Posted by Siggy

I had to unplug the battery to get it all to stop...

I know this is the only way you have to kill this possessed beast, but ... My understanding is that:

back in the olden days, you could disconnect a battery from a running engine, and the generator / alternator would gladly keep it going with no problems.

On more modern cars, disconnecting the battery can cause voltage spikes that can damage the alternator and other voltage-sensitive components throughout the car. I actually experienced this once on an old 911 with a loosened battery clamp. So for you, you might consider that problems may be worsening as you proceed due to this - e.g., a weak, flaky diode may end up being killed.

So I never intentionally disconnect a battery cable from a running engine, but in this case, since you have to ... Should it kill the engine (as it does - other than in post #90)?

On the basic high-current wiring in the front there ...

There are at least two different ways BMW did it on E53s, I think choosing based on whether a water cooled alternator is used vs. air cooled. Some official-looking BMW info out there may be wrong in this area.

On the air-cooled alternators like you and I have, the fat +12V cable comes from the battery, passes into the engine bay through that B+ jump port, then down to the starter, then on to the alternator where it terminates. The alternator and starter are each grounded by being connected to the engine block, which is grounded.

[Siggy]

I haven't had the car too long, it was cheap at the time and about everything was wrong with it. Every light in the dash was on, the A/C didn't work, all the buttons were missing off the A/C controls. In looking through it, I found registration documents for the last 2 owners. Neither appeared to have the car long.

When I got it, it almost immediately had the "dead battery" situation. I had it tested and they told me it failed under load. I put new battery in it and that one wasn't in there long, and went bad. Took it to be tested, "failed under load", and I just took the one that replaced that in and it "failed under load".

My thought is whatever is causing the issues is smoking the batteries. I also suspect the reason I own it now is because no one else wanted to take the time to figure it out or couldn't afford to take it to the dealer.

It doesn't appear to have anything aftermarket on it. The only thing I did see was a line splitter connector coming off 1 wire that goes into the OBD plug. The connector is still spliced into the wire but there's no additional wire going anywhere so I don't know what that was for. It's factory radio, factory speakers, factory nav. I don't see anything that's aftermarket on the car.

Remind me, it's been a while since I was really under the car. I need to take the pan off the bottom to see the starter right? I've had the pan off before and I remember seeing the starter, but I don't recall if that was all at the same time.

[Overboost]

Originally Posted by Siggy

Remind me, it's been a while since I was really under the car. I need to take the pan off the bottom to see the starter right? I've had the pan off before and I remember seeing the starter, but I don't recall if that was all at the same time.

The starter is under the intake manifold on the M54. You can see a glimpse of it under the car but if you want to change it, be ready to remove the intake manifold.

[Siggy]

Thanks! No plans on removing it, just tracing wires and want to put my eyes and hands on the wires.

[cn90]

Originally Posted by Siggy

2006 3.0 with 156,000 miles on it...
Put another ignition switch in it tonight, buttoned it back up, started it, it started right up. Turned the key off and it kept running. Pulled the key out and it kept running. Clearly I'm missing something here.

It's a good, newer battery (less than a year old), new alternator, 2 new ignition switches.

I did not have time to go through 10 pages.
However, I think it is the tumbler part.