jlopret

I have a 535xi with 148k miles on it. Everything runs and drives fine but recently i've been having electrical issues.

Since I’ve had the car the time wouldn’t keep, or I have to set it. Two weeks ago, I installed a subwoofer and amp (nothing crazy). It ran fine that night so the next day it drove to the store and when I got back into the car and put, they key into the ignition nothing happened. No lights, no dings, no idrive, and no start. The car was absolutely dead as if there was no battery in it. The key was stuck in the ignition, so I pulled out the removable key from the fob and went into the trunk. Everything looked fine in the battery compartment and auto zone tested the battery (luckily, I was in the parking lot when it happened) and they said it was a good battery. So, stranded there knowing the battery still had juice I disconnected the negative terminal and put it back on and everything worked for the drive home. I pulled onto my block and I got 4 error messages in I drive. Increased battery discharge, something about the window regulator, gear selector malfunction, and awd/dsc malfunction. I got into my driveway and went to shut off the car and it died and the only way to get it back on was removing the ground from the battery and putting it back on. I cleaned the terminals and went back to auto zone and bought a new battery even though after cleaning the terminals it stopped losing power. Now two weeks later I get to the store and same thing happened. I removed the ground off the battery and put it back car fired up but I heard a weird crack from the speakers and had no sound from the radio or dings. I turned off the car and back on and everything worked as normal. I can’t get the car to replicate the problem again.



Timeline:

-The time problem and error messages were only with the old battery.

-Complete electrical power loss started after amp install.

-New battery installed 2 weeks ago and still lost time but no error messages.

-Complete electrical power loss and sound loss with new battery.



Battery voltage is at 12.4 when off, steps down to 10.4-11v during start up and alternator keeps everything steady at 14.2 when running.



I’ve been reading forums about the IBS and I’ve been having similar problems with the time not staying but people with that problem are reporting the car just won’t crank over (their interior lights go on) not complete electrical failure upon inserting the key fob.



It almost seems like when it goes to prime the fuel pump when the key is inserted it fails and it needs to be reset by disconnecting and reconnecting the battery.



Thank you all for all the responses and help in advanced.

seanjordan20

Try disconnecting the amp you installed and whatever else to try and isolate the issue. If after a couple days you still get the issue then you have to find where the drain is.

You could be dealing with one issue and after installing the amp added another issue.

jlopret

thank you,
I noticed that when the car was off the amp stayed on for a couple min and periodically went back on with the random electronic sounds it makes so i switched the remote wire to the amp to a true 12v switch (the dc plug in the trunk) so it goes off with the key. Im going to run that for a couple of days and see if it happens again then the amp is going to get disconnected if that doesn't fix it. This might be a dumb question but i know its a bmw so you never know. Is there a special place in the car where the positive wire for the amp should go besides the battery? i ask that only because bmw's can be very problematic if you do something its not suppose to

seanjordan20

No I've only seen the power coming from the battery.

Dj530

Your title says " can bus and battery drain", what kind of voltage readings are you getting from the can bus wires?