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BMW E34 5-Series and E32 7-Series Locked Out – Dead Battery Emergency Entry

August 24, 2010

I’ve got this serious problem with my 92 535i. The central locking system has shut down and my doors are locked. I can only open the trunk. The trunk will not lock at all. I’ve tried the key in both doors…..the key does bounce back but the latch does not release. Also my battery has run down, (not sure if the locking sys. runs off the battery.) Is there any thing I can do from the inside of the trunk to open the doors.


This answer applies to all BMW E34 (5-series 89-96, 525i, 525it, 530i, 530it, 535i, 540i, M5) and E32 (7-series 88-93, 735i, 735il, 740i, 740il, 750il) models.

We have four different procedures that you can try in order to gain entry to an E34 or E32 BMW that has a dead battery, and the doors are locked.

1)  Emergency key entry:  This should work on most E34 (5-series 89-96) and E32 (7-series 88-94) models, when you have a dead battery.  At the passenger door, insert the key, pull up the door handle and then turn the key to the unlock position. This should unlock the door. Note that we have talked to E34 & E32 owners who have not been able to gain entry using this method.  If this does not work, see the procedures below.

2)  If the trunk can be opened, we can apply 12-volts (from another battery) to the positive wire for the trunk illumination lights.  At either of the tail light harness plugs or the trunk lid light, apply the positive from your remote battery to the red/white wire (this is the trunk illumination lighting circuit).  Connect the negative from the battery to a good chassis ground or any brown wire.  As long as the vehicle battery is not so dead that it is internally shorted, this should put enough power into the system to allow the door locks to function.

3)  Similar to the #2 above, we can apply 12-volts to the black/red wire for the central locking system.  The trunk lock actuator is mounted in the trunk lid.  The harness plug for the actuator will have a black/red wire.  Apply the positive from your remote battery to this wire and the negative to a chassis ground or any brown wire.  As long as the vehicle battery is not so dead that it is internally shorted, this should put enough power into the system to allow the door locks to function.

If the battery is so dead that the above steps do not work, you will need to apply enough power from your remote battery (or a charger) to put a bit of charge into the vehicle battery.  This can be done as follows:

4)  Jack up and safely support the front of the vehicle, so that you can get under the engine compartment.  Apply the positive cable from your remote battery (or charger) to the large positive terminal on the starter solenoid or the positive output terminal on the rear of the alternator.  Connect the negative to a good chassis grounding point.  If the locks do not work right away, give some time for the vehicle battery to gain a bit of charge and then try again.

  1. Damir permalink

    Hi. I have the same problem.

    Tomorrow, I will try to connect one external battery .

    the negative on the body
    the positive to the positive pin of lamp in the trunk.

    I think that it will open the doors.

    I will keep you informed



  2. timster permalink

    Any luck?
    I am having same problem.1990 525I
    Left lights on doors locked.
    The manual method to open the doors is not working.
    Can get into trunk.
    Anyone know if you can get through the back seat?

    • There is no easy access to the cabin, via the trunk. We have heard of people affixing a spare battery to the positive terminal on the starter (the one that the batter cable connects to) and negative to a good ground on the chassis, using wires and a small slip or clamp on the starter terminal. Of course, this must be done from under the car. This procedure should allow enough power into the system (via the cable from the starter, back to the battery), to get the doors to unlock.

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