Battery drain led to no start?

Artemas · 10-17-2025, 02:06 PM

I need help with my BMW N54 E92 2008. About a month ago I left the lights on and the battery drained overnight. The next day I jumpstarted it with my truck and the car started fine. I drove it to work and everything seemed normal.
When I came off work I tried to jumpstart it again in the parking lot. This time the car did crank but it never fully started. After that moment it stopped cranking at all. I had it towed back to my house.
Since then I have replaced the starter and the battery. I also tried a ground strap bypass by putting jumper cables on both ends of the strap, but it still would not start. That might have been when the battery voltage was low though.
Now when I press and hold the start button, all I hear is a click from the fuse box in the glovebox. The starter itself does not make any sound at all.
One more thing I noticed: the OBD port only shows about 11.7 volts, but the ECU is seeing closer to 12.5 volts.
So the issue started as a battery drain, then it cranked but would not start, and now it has turned into no crank and no start even after replacing the starter and the battery.
Could this be a fuse, the junction box, or something else in the power path?

lookalikehuuh · 10-19-2025, 12:53 AM

So first thing is first, if you don't already have one, you need to acquire a BMW specific scan tool that can read more than just "P" codes like cheap Amazon OBDII readers. It will pay for itself 50x over in the first year.

After you get that tool, you can scan for codes, it will give you tons of clues to what the issue preventing your car from starting is.

Artemas · 10-19-2025, 12:56 AM

Quote:

Originally Posted by lookalikehuuh

So first thing is first, if you don't already have one, you need to acquire a BMW specific scan tool that can read more than just "P" codes like cheap Amazon OBDII readers. It will pay for itself 50x over in the first year.

After you get that tool, you can scan for codes, it will give you tons of clues to what the issue preventing your car from starting is.

I got these 3 codes with an app but if you can point me to a good scanner id appreciate it!

10-17-2025, 02:06 PM	#1
Artemas New Member 0 Rep 30 Posts Drives: E92 335i Join Date: May 2024 Location: Fairfax VA iTrader: (0)	Battery drain led to no start? I need help with my BMW N54 E92 2008. About a month ago I left the lights on and the battery drained overnight. The next day I jumpstarted it with my truck and the car started fine. I drove it to work and everything seemed normal. When I came off work I tried to jumpstart it again in the parking lot. This time the car did crank but it never fully started. After that moment it stopped cranking at all. I had it towed back to my house. Since then I have replaced the starter and the battery. I also tried a ground strap bypass by putting jumper cables on both ends of the strap, but it still would not start. That might have been when the battery voltage was low though. Now when I press and hold the start button, all I hear is a click from the fuse box in the glovebox. The starter itself does not make any sound at all. One more thing I noticed: the OBD port only shows about 11.7 volts, but the ECU is seeing closer to 12.5 volts. So the issue started as a battery drain, then it cranked but would not start, and now it has turned into no crank and no start even after replacing the starter and the battery. Could this be a fuse, the junction box, or something else in the power path?
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10-19-2025, 12:53 AM	#2
lookalikehuuh Colonel 1884 Rep 2,177 Posts Drives: 2006 330i, 2007 335i Join Date: Sep 2014 Location: San Diego, CA iTrader: (0)	So first thing is first, if you don't already have one, you need to acquire a BMW specific scan tool that can read more than just "P" codes like cheap Amazon OBDII readers. It will pay for itself 50x over in the first year. After you get that tool, you can scan for codes, it will give you tons of clues to what the issue preventing your car from starting is.
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