BMW Troubleshooting

[Nanometer]

Hey Hope I can find some help here...

Basically I was driving my X5 today and all of a sudden the car reported no DSC, no ABS, and then the Park Brake lights in the gauge cluster lit up. Additionally, the iDrive reported some sort of 4X4 issue.
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Now I didn't feel anything "break" so to speak. Was just cruising when the issue occurred. Only error code that popped up with P15B9, something about intake manifold leak, which does not appear to be released.
Any thoughts on this? Thanks in advance!

[Thecastle]

Bad battery and or bad alternator

[NorthCountryGuy]

Had a similar situation. My 650 was running well. Suddenly DSC, Transmission overheating warning (car was just started), Drivetrain Malfunction. Car went into Safe Mode. Only BMW code was crankshaft signal implausible. Changed the crankshaft sensor and still the same. Engine would go into Safe Mode. I looked and did what I could, but to no avail. Took it to my Indy. Took him 2 full days, but he found the cause. A bolt to the engine block was missing. This bolt grounded part of the harness for the coils on one bank. Overwhelmed the DME. Car now running like a charm (I now just had a vision of the lightning bolt to come...). Sounds electrical. From my experience with an old Porsche, ground maintenance is crucial.
Check battery status. Check alternator voltage while running. Examine grounds. Engine block ground to chassis low down on drivers side above hemi axle. Search. I posted on thread on servicing it.

Add: https://www.xbimmers.com/forums/show....php?t=1632755

[Nanometer]

Hey Thanks for the responses! The issue completely went away without me doing anything the following day. No error codes anymore, and the drivetrain issues went away. Could be battery or alternator. But it was interesting that it happened during a time that the better had not been sitting. Happened during a long drive. So maybe alternator. I suspect original battery which is around 6 years old, but Ill double check.

[Molez93]

A lot of my seemingly random BMW electrical issues have been solved over the years by replacing the battery. Lots of X5s, but some others too... same thing. If the errors don't otherwise make sense and the battery is (or might be) 3+ years old, I have had great luck just installing a new one.

Good luck!

[Nanometer]

So I replaced the battery 2 days ago, and have since logged about 3 hours of mostly highway driving. However, I am still getting voltage dips which is causing the faults. as soon as the voltage dipped below 11.9 or so I got the ABS fault light and bunch of other lights like DSC, Park brake, etc. See attached log of the voltage. Any thoughts? I was reading somewhere that ignition coils could cause this? They are factory original. What about anything else? Alternator seems to work.. just not charging at the right voltage when its supposed to!
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Also, battery seems to spend way too much time at low voltage, check out the 6 minute mark to 8 minute, where it averages around 12.2

[NorthCountryGuy]

This looks like a read out of defective alternator output. Should be reading around 14V with minor fluctuations. You have fluctuations down to battery voltage.

[Sophisticated Redneck]

Like NCG Said, could be defective alternator. Could also be BMW's absolutely mental battery management software. To try in get that .05% extra efficiency, the Alternator is only used in times of braking/coasting or excessive low voltage. I too have seen mine dip to 12.1 when on long cruises on the highway with no slow downs or braking. Turning on your headlights AND foglights overrides this crap and forces the alternator on. Try it for yourself. I always drive with my lights on now and my battery voltage never fluctuates, before it bounced all over the place anytime I braked or coasted. Ever notice your cabin fan speed increase when you brake? Now you know why. If even with the lights and fog lights on the voltage is still fluctuating, then most likely is your Alternator. Double check your main engine ground cable too which is located on the drivers side by the engine mount/steering rack. Its hard to see but a known failure point for electrical gremlins

[Nanometer]

I haven't noticed any change in fan speeds for A/C. I am going to have a tech check out some of the alternator parameters. It is just odd that the car allows the battery to drop so low, below 12.8V while running. I agree that it should always be higher than 13.1 for a healthy alternator, and not dropping below that, which mine is doing quite a lot. I do notice that the Voltage goes up when costing/braking, as it should. but sometimes when I hit the gas, I see dips into 12.5V which sounds very odd. I feel like it is not a defective alternator, because it shouldnt be so consistent with braking/costing if it were bad. It sounds to me like crappy software which I am not so sure of, a bad regulator, or some other hardware issue potentially. I'll keep looking! Hope I don't kill this battery... drive this morning was mostly okay, except for first 5 mins when voltage dropped to 12.2 momentarily.

[Nanometer]

How do you check the grounding strap? Where is it located? And how do you know if it's good or bad?

[heatmizr]

As above, by design the alternator charges only under certain parameters, and not under others. I am not familiar with a graph that shows exactly this, but your graph would seem to match what I would expect.
So possibly that alternator/charging battery management system IS working, but your alternator output is lower than it ought to be overall?
Not sure how an alternator would put out current but a little less than spec, seems more likely it would fail altogether instead...
What else could reduce the current, but still allow some through? A corroded ground or other connection?
What year is your X5?

[TwinSnailz]

Originally Posted by Nanometer

How do you check the grounding strap? Where is it located? And how do you know if it's good or bad?

Right above the driver side front differential. A bad strap will turn to a blue-ish/green color. This is a necessary item to replace. No if ands or buts. When it fail, it will leave you stranded(no start). But counter-bmw engineering like me figured out how to jump start this sucker if it ever failed.
“ ground the jump wire on an engine bolt” since theres no ground wire to the engine because it has failed.

[NorthCountryGuy]

Read posts.
See #3 above.

[Nanometer]

Thanks for the tips! The shop I had it at claim an intermittent ABS sensor may have been the culprit.. though I don't understand how that could possibly interfere with charging. Will provide an update to see if that really fixed it.