[Hauteknits]

Hey guys, I was pulling out of my parking structure after just driving the car about 5 hours ago, when I noticed that my power steering suddenly gave out. Then roughly 5-10 seconds later the engine stops and wouldn't crank. No weird noises, no smells, no fluid leaks, and no DTC codes. Battery voltage was fine (now sorta low due to crank attemps). Car wont crank at all, similar sounds and symptoms to dead battery. Battery is 9mo old, followed all the BMW battery procedures when replacing. Any thoughts as to what happened? Just due to how the event happened I'm a little nervous to crank the car again, got an oil change around 1500 mi ago

[Spooly]

I’m no expert but sounds electrical to me. I’d check your voltages, confirm your alternator is good. Check your belts. Check wiring. If you can get a laptop with ISTA, I’d do that and follow the diagnostic procedures on there.
If you’re really nervous to crank it, which I don’t think you should be, you can pull the plugs and look at them and change the oil to confirm no metal. If you spun a bearing, I don’t see how your power steering pump would give out first.

[Hauteknits]

I'll hop in ISTA and do some poking around. I'll double check the wiring as I did use some positaps while installing a WOTBox, but I've disconnected the WOTBox from the ignition and all of the DME wires appear to be fine (pedal and clutch source are confirmed working good, no way to verify crank position sensor currently). Serpentine belt appears fine and the timing chain appears taut. Hopefully electrical

[Xalithar]

It almost sounds like the car is not wanting to recognize your key any more. If you have a spare try that one and see if it works.

[yupetc]

Alternator would be my first assessed guess. You can try to charge up the battery again or use a high amperage battery supply to see if it come to life again. If it does, use an OBDII dongle and view the alternator voltage while the engine can still run. Many free apps allow you to view the voltages.

[Hauteknits]

Originally Posted by Xalithar

It almost sounds like the car is not wanting to recognize your key any more. If you have a spare try that one and see if it works.

I don't have a spare, but key buttons work fine and I can turn on both accessory and ignition, currently leaning towards Alternator

[Hauteknits]

Originally Posted by Spooly

I’m no expert but sounds electrical to me. I’d check your voltages, confirm your alternator is good. Check your belts. Check wiring. If you can get a laptop with ISTA, I’d do that and follow the diagnostic procedures on there.
If you’re really nervous to crank it, which I don’t think you should be, you can pull the plugs and look at them and change the oil to confirm no metal. If you spun a bearing, I don’t see how your power steering pump would give out first.

ISTA didn't show much of anything, but then again I'm not sure exactly what I'm looking for. Voltages are fine, belts are fine. I'm currently at my friends appt parking structure where I broke down, and I cant really get a jack and jack stands for oil check there

[Hauteknits]

Ended up taking to a shop. Couldn't see it at the time but the tensioner gave out and the serp belt locked itself around the crank pulley. Got it all replaced but after a single WOT pull the belt shredded itself again with same symptoms as before. Something is likely binding in the serp belt path and causing it. My money is on the alternator since it looked like it was splitting at the seam but going to wait to hear back. At least I didn't spin a bearing

[Spooly]

Originally Posted by Hauteknits

Ended up taking to a shop. Couldn't see it at the time but the tensioner gave out and the serp belt locked itself around the crank pulley. Got it all replaced but after a single WOT pull the belt shredded itself again with same symptoms as before. Something is likely binding in the serp belt path and causing it. My money is on the alternator since it looked like it was splitting at the seam but going to wait to hear back. At least I didn't spin a bearing

Glad to hear it you've got it figured out, and glad it wasn't worse. I've heard horror stories about the belt being sucked in through the front main seal.