128i looses ALL electrical at random, if I just wait an hour it ALL comes back.

[E70E90E88]

Here is an interesting one. My E88 has started doing this goofy nightmare issue where the car will loose ALL electrical. I only show power at the battery and at the jumper terminal under the hood.

If I wait about an hour it will at random start working again. I have been standing next to it when it just springs right back to life without anyone touching anything. New battery as the old one was overdue but the old battery also did it. The other day while driving the ABS light came on along with a bunch of other lights on the dash (combi module maybe?) but then while driving they all turned off and everything was normal again. I had the chime along with all the lights and errors and within 2 second all disappeared like they never even existed. Engine never missed a beat.

Sometimes it will go for months without causing any issue and other times it will do this dead car trick four times in one day.

I did notice one time when I pulled and re plugged in the 50A fuse behind the glove box and within 5 seconds the entire care came back to life. That said the last time it did the dead car trick that did not solve it the second time.

I am thinking the main computer, or maybe some kind of distribution box or relay system someplace. It does not have an alarm so it is not that going south.

I have latterly just sat in the car and waited, catch a few Z's waiting and BAM it just comes back to life at random times and starts and runs like normal.

Pulling the battery and reconnecting it does nothing. I can pull the batter for 45 mins and nothing, or I can just leave it alone and in about an hour it all comes back to life like normal.

Any ideas? Anyone seen this on the E88 or maybe the E90 cars?

Thanks in advance.

[Tuxedo]

there was a battery cable recall about 5yrs ago, make sure it was done. I'll poke around Monday for any ideas

[JimVonBaden]

Check the passenger side under the hood where the battery cables meet.


Near the red piece. One of the cables there gets loose.

[Stubbie Blue]

I had a similar thing happen to me, just driving then randomly get a chime, ABS warning, brake warning, and a few others. Then after a second it just disappears and goes back to normal. Once I hit a big bump and all that happened as well as my headlights going off and my radio lost power. I did check the brake fluid level and it was ok and changed around 1.5 yrs ago.

The only thing I've done recently was install an Android headunit and backup cam that I hooked up directly to the positive battery terminal so I retightened it to the 5 Nm spec (44 inch pounds) a couple of days ago, and it hasn't happened since, but I'll have to wait and see because maybe it could shake loose.

[Big boi m5]

I've seen watereak into the trunk and short wires.