Step-by-Step: How to Open F80 Trunk with Dead/Disconnected Battery

[jonnyfive]

This seems to be a rite of passage for M3 owners: closing the trunk while working on the car with a disconnected battery. In my extensive searching on the forums for advice on how to remedy this situation, I found no solutions that worked for me, but I did find that many others had made this same mistake as I did.

The obvious answer is to use the terminals under the hood of the car to supply power to your car, by hooking up jumper cables to another car or to an external power supply. For whatever reason, this did not work for me, at all. I tried two cars, and two sets of jumper cables, just to make sure those items were not the issue. No dice.

I also learned that the F80 has no lock cylinder on the trunk. Older models may have a lock, and if so you, could be in business.

Some other poor sap on the forums actually drilled a hole through his trunk lid to gain access. That's just crazy. Don't do that. Ever.

The tech savvy solution to this is to tap into the appropriate wire in your car and apply power with an external battery, thus powering the trunk enough to release it. The only writeup I could find on this was for an older model car, and so the wiring schematics did not apply for me. This sounded feasible and likely would have been my last resort, but I would have called a professional to handle this for me, as I just didn't have the patience left to pore over electrical schematics and figure this out.

In my despair I decided that perhaps I could remove enough of my rear seats to gain access to my trunk. Some older models have a "ski access" in the center of the seats that could be your solution - but for newer M3's this is not available. Since the seat releases are inside the trunk, I thought maybe if I could remove every other point of attachment, that I could pivot the seat(s) up just enough to give me access.

The side bolsters and the seat bottom all just pop straight off, and are easy enough to remove. This leaves just the two seat backs. I found a lone Torx 50 bolt attaching each seat on either side. This could be it! I removed the bolts, yanked on the seats...and found that they were connected in the center by a rod, through a hard point welded to the frame of the car. I could not for the life of me figure out how to remove that rod from between the seats. It seemed all was lost.

I started poking around with my phone on the inside of the trunk, through a gap in the seats, trying to take video and see what I could see. It's a new car for me, so I'm not terribly familiar with any cable routing. Lo and behold, dangling in the rear, center of the trunk lid, was the manual trunk release! The largest gap in the seats you can create is at the driver side bottom corner. I stuck a flashlight in that gap to light the trunk, and prop the seat open. I then rigged up a clothes hanger hook, but even at full extension it was not long enough to reach. So I grabbed one of my golf clubs, masking taped the hanger to the club, and was able to then reach the release. Massive crisis, somehow averted.

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[rakusak]

Thanks for the insight... curious to see what others have done...

Is the moral of the story to fold seats down whenever disconnecting battery?

[domino_z]

thanks for this mate

i just installed the bimmertech power trunk and was wondering how i'd open the trunk if the latch ever fails

[dm874]

I actually used this same exact method except I used a broom stick instead of a golf club. I had the same issue with the jumpers in the front not working. When I finally opened the trunk I noticed that the negative battery wire was touching the body of the car. I think this caused a short and would not allow the car to be jumped from the front. I had to get in through my back seats as well. I felt bad for not writing up a diy a few months ago on this but now I can sleep better at night knowing there's now one out there.

[Nomana]

i did it once however there is no hook inside the trunk but i can open the hood so i call bmw road assistant and did jump start.

[newnmpr0ved]

Instead of using the hook to pull the trunk release,
Its easier to use the golf club or anything similiar in length to push the seat release lever, then u can climb in and pull the yellow trunk release. I can't believe my dumbass forgot to reconnect the battery.

[dinonz]

I think someone should create a small plastic cover for the trunk closing mechanism that can live in the battery compartment, and when you disconnect the battery you take this little piece of plastic and cover your trunk latch with it - means you will not be able to close the trunk even by accident. Unless you stupidly remove the block before you reconnect the battery.

[Frode D]

Good to know. I have done this in a previous car and had a massive struggle to open it again.

My solution: Always pop the seat back when disconnecting the battery.

[ArieArie]

Originally Posted by jonnyfive

This seems to be a rite of passage for M3 owners: closing the trunk while working on the car with a disconnected battery. In my extensive searching on the forums for advice on how to remedy this situation, I found no solutions that worked for me, but I did find that many others had made this same mistake as I did.

The obvious answer is to use the terminals under the hood of the car to supply power to your car, by hooking up jumper cables to another car or to an external power supply. For whatever reason, this did not work for me, at all. I tried two cars, and two sets of jumper cables, just to make sure those items were not the issue. No dice.

I also learned that the F80 has no lock cylinder on the trunk. Older models may have a lock, and if so you, could be in business.

Some other poor sap on the forums actually drilled a hole through his trunk lid to gain access. That's just crazy. Don't do that. Ever.

The tech savvy solution to this is to tap into the appropriate wire in your car and apply power with an external battery, thus powering the trunk enough to release it. The only writeup I could find on this was for an older model car, and so the wiring schematics did not apply for me. This sounded feasible and likely would have been my last resort, but I would have called a professional to handle this for me, as I just didn't have the patience left to pore over electrical schematics and figure this out.

In my despair I decided that perhaps I could remove enough of my rear seats to gain access to my trunk. Some older models have a "ski access" in the center of the seats that could be your solution - but for newer M3's this is not available. Since the seat releases are inside the trunk, I thought maybe if I could remove every other point of attachment, that I could pivot the seat(s) up just enough to give me access.

The side bolsters and the seat bottom all just pop straight off, and are easy enough to remove. This leaves just the two seat backs. I found a lone Torx 50 bolt attaching each seat on either side. This could be it! I removed the bolts, yanked on the seats...and found that they were connected in the center by a rod, through a hard point welded to the frame of the car. I could not for the life of me figure out how to remove that rod from between the seats. It seemed all was lost.

I started poking around with my phone on the inside of the trunk, through a gap in the seats, trying to take video and see what I could see. It's a new car for me, so I'm not terribly familiar with any cable routing. Lo and behold, dangling in the rear, center of the trunk lid, was the manual trunk release! The largest gap in the seats you can create is at the driver side bottom corner. I stuck a flashlight in that gap to light the trunk, and prop the seat open. I then rigged up a clothes hanger hook, but even at full extension it was not long enough to reach. So I grabbed one of my golf clubs, masking taped the hanger to the club, and was able to then reach the release. Massive crisis, somehow averted.

I probably do not understand the problem.
But if I can open the car's doors, I can also pop the hood and use jumper cables to power the car, and pop the trunk. Would this work?

[zaynn786]

Originally Posted by jonnyfive

This seems to be a rite of passage for M3 owners: closing the trunk while working on the car with a disconnected battery. In my extensive searching on the forums for advice on how to remedy this situation, I found no solutions that worked for me, but I did find that many others had made this same mistake as I did.

The obvious answer is to use the terminals under the hood of the car to supply power to your car, by hooking up jumper cables to another car or to an external power supply. For whatever reason, this did not work for me, at all. I tried two cars, and two sets of jumper cables, just to make sure those items were not the issue. No dice.

I also learned that the F80 has no lock cylinder on the trunk. Older models may have a lock, and if so you, could be in business.

Some other poor sap on the forums actually drilled a hole through his trunk lid to gain access. That's just crazy. Don't do that. Ever.

The tech savvy solution to this is to tap into the appropriate wire in your car and apply power with an external battery, thus powering the trunk enough to release it. The only writeup I could find on this was for an older model car, and so the wiring schematics did not apply for me. This sounded feasible and likely would have been my last resort, but I would have called a professional to handle this for me, as I just didn't have the patience left to pore over electrical schematics and figure this out.

In my despair I decided that perhaps I could remove enough of my rear seats to gain access to my trunk. Some older models have a "ski access" in the center of the seats that could be your solution - but for newer M3's this is not available. Since the seat releases are inside the trunk, I thought maybe if I could remove every other point of attachment, that I could pivot the seat(s) up just enough to give me access.

The side bolsters and the seat bottom all just pop straight off, and are easy enough to remove. This leaves just the two seat backs. I found a lone Torx 50 bolt attaching each seat on either side. This could be it! I removed the bolts, yanked on the seats...and found that they were connected in the center by a rod, through a hard point welded to the frame of the car. I could not for the life of me figure out how to remove that rod from between the seats. It seemed all was lost.

I started poking around with my phone on the inside of the trunk, through a gap in the seats, trying to take video and see what I could see. It's a new car for me, so I'm not terribly familiar with any cable routing. Lo and behold, dangling in the rear, center of the trunk lid, was the manual trunk release! The largest gap in the seats you can create is at the driver side bottom corner. I stuck a flashlight in that gap to light the trunk, and prop the seat open. I then rigged up a clothes hanger hook, but even at full extension it was not long enough to reach. So I grabbed one of my golf clubs, masking taped the hanger to the club, and was able to then reach the release. Massive crisis, somehow averted.

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I'm in a very similar situation with my F30. I was retrofitting LCI lights into my car and unplugged a module in the REM A174*13B which controls trunk realise I think. Anyways shut the boot and forgot to connect this plug and have no access to my trunk. I've took it the dealers but I don't think my car hasn't the emergency trunk release as I am in the UK. Be interesting to see what the dealers do lol

[danniexi]

Originally Posted by ArieArie

I probably do not understand the problem.
But if I can open the car's doors, I can also pop the hood and use jumper cables to power the car, and pop the trunk. Would this work?

it didn't work for OP.

that being said, i did the same stupid thing (disconnect battery and close trunk). buddy had jumper cables, so we popped the hood, connected the cables, and once he started his car i immediately kept pressing the trunk release button on my key fob which thankfully worked. trunk open i hooked up the battery and all was well.

[dubsesd]

So much effort just to get that pre workout powder , haha

[dzvero]

Or one can use jump start cables and another car to be able to open trunk which might be easier in some cases

[dubsesd]

Originally Posted by dzvero

Or one can use jump start cables and another car to be able to open trunk which might be easier in some cases

You didn't read the thread. OP tried that with 2 cars and cables and it didn't work for him

[M4DNS55]

Can anyone help here with an M4? I assume it would be similar to an M3? There seems to be some pictures missing from the guide...

[kubax86]

Originally Posted by M4DNS55

Can anyone help here with an M4? I assume it would be similar to an M3? There seems to be some pictures missing from the guide...

You can open the hood, and connect any battery using jumper cables. That will provide power to the car - you will be able to open trunk afterwards.

[M4DNS55]

Originally Posted by kubax86

You can open the hood, and connect any battery using jumper cables. That will provide power to the car - you will be able to open trunk afterwards.

I had my car on the trickle charger anyway and car would start.

The issue was that I didn't connect the wiring loom connection to the boot release so had no power going to it...

[kubax86]

Originally Posted by M4DNS55

I had my car on the trickle charger anyway and car would start.

The issue was that I didn't connect the wiring loom connection to the boot release so had no power going to it...

Trickle charger won't recognize battery.
Just simply connect another battery by jumper cables.

Thanks

[M4DNS55]

Originally Posted by kubax86

Trickle charger won't recognize battery.
Just simply connect another battery by jumper cables.

Thanks

But that won't help if there is no power running to the boot release.... Because the wiring loom is not connected to it....

[thestimp]

In the E series model, maybe f? I know this works because I've done it, the rear drivers speaker in the back window has the seat cable release wire that you can get to and pull so the seats unlock. It takes all of 5 mins to do if you have access to inside the car. Somewhere in my post history is the step by step.

[Jbrown7403]

I have always been paranoid that I would close my trunk after disconnecting my battery so first thing I do is tie microfiber towel around this...

[tom @ eas]

necro bump.

Easiest way to open trunk is to remove the trunk handle, which will allow you to reach the emergency trunk release with a reach tool. License plate needs to be removed to allow clearance for the trunk handle to pop out.