Tries to start but the battery is discharging very quickly

MIKEHAWK

MEMBER
2007 BMW 525I
3.0L
V6
2WD
AUTOMATIC
130,000 MILES

Tries to start and nothing. Changed ignition coils, spark plugs, gas pump, starter, alternator, voltronic pending. Now I'm having an issue with battery discharging very quickly. Changed battery, now new one is acting out the same. So back to beginning it started with a fault code P0306, misfire cylinder 6 and a too lean code bank 2 then went to battery discharging. Now I can't use obd2 scan tool. Help!

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

If you just replaced the battery then we need to check the condition of it with a load test and then put a good battery in it.

https://www.2carpros.com/articles/car-battery-load-test

Then we need to do what is called a draw test. You do this by disconnecting the negative battery cable and connecting you voltmeter in line by connecting one lead to the battery post and the other lead to the negative cable. Set your meter to amperage and then open the doors so you can access the fuse panels but flip the door latch or ajar switch so that the vehicle things the doors are closed.

Once you have this set up you need to start pulling fuses until you find the one that causes the draw to drop below .030 amps (30 milliamps).

https://www.2carpros.com/articles/car-battery-dead-overnight

Once we find what fuse it is we can go from there. Let me know if you have questions. Thanks