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2Addicts | BMW 2-Series forum Technical Topics Mechanical Maintenance and TSBs: Break-in | Oil & Fluids | Servicing | TSB Battery Disconnected - Trunk Shut - Can't Jump Car

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      01-22-2022, 08:42 PM   #1
redgt00
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Battery Disconnected - Trunk Shut - Can't Jump Car

Hey all, first post here! Looking for some help.

I've got a 2016 M235i. Today, I did a valve cover gasket replacement to fix a small oil leak. The job went great, but I'm having trouble getting power back to the vehicle.

The night before, I disconnected the positive terminal on the battery in the trunk to help relieve fuel pressure. With this being my first BMW, I shut the trunk right afterwards...It didn't take long to realize that I couldn't get it back open.

When I disconnected the battery, the car lost power as it should, but a fan started blowing on the passenger side behind the glove box. I'm guessing this is the AC blower fan or something. It went for 5+ hours before I went to sleep. It was off in the morning. I tried to figure out how to shut it down, but had no luck.

Once I completed the job, I knew I needed to jump the car to open the trunk (can't go through backseat). I tried jumper cables from a running car as well as a battery booster/charger. No luck. However, when I put the booster on the terminals under the hood, the blower fan started going again. I'm getting absolutely no power inside the vehicle cabin but am measuring 12-12.5 volts at the positive terminal in the engine bay without anything hooked up to it.

I should also add that I've been over all my work numerous times and everything seems to be plugged back in just as it was.

Any help would be very much appreciated! I'm a fairly competent DIY mechanic, but this one has got me really stumped.
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      01-23-2022, 10:27 AM   #2
John in VA
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I'm surprised you can't get enough juice from connecting a battery or jump pack under the hood to pop the trunk from the fob or trunk switch - that's what those jump posts are meant for. Is it possible you have a valet lock in the glove box that is preventing the trunk from opening?

By the way - you should always disconnect the negative terminal from the battery first - the positive cable will be live & could short something.
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      01-23-2022, 10:57 AM   #3
redgt00
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Quote:
Originally Posted by John in VA View Post
I'm surprised you can't get enough juice from connecting a battery or jump pack under the hood to pop the trunk from the fob or trunk switch - that's what those jump posts are meant for. Is it possible you have a valet lock in the glove box that is preventing the trunk from opening?

By the way - you should always disconnect the negative terminal from the battery first - the positive cable will be live & could short something.
Hey John, appreciate the reply. You're right on the negative terminal. Not sure why I did the positive this time. I think at some point in my mind I started thinking you're supposed to remove the pos...

The switch in the glove box has the trunk set to unlocked.

When I hookup the booster, it doesn't give any power to the vehicle at all, which I find very odd. The only thing that happens is that a fan on the PS starts blowing. You can feel air coming out of the vents inside.

From what I've read, you're supposed to be able to get power to the car this way. I'm starting to think that this isn't working because the positive terminal is disconnected.

I've been attempting to remove the rear seat, but with no luck. The bottom popped right off. Next I removed the side bolsters. I then removed the two torx bolts on the lower left/right sides. It seems the seat back is latched to something in the center and won't come loose. I'm pretty sure you need to pop a latch in the trunk. The seat is one whole piece that looks like it folds down. I've tried getting something up behind the seat but with no luck. Can't see in there either.

Seems to me I need to find a way to tap into the switch to pop the trunk. If I could supply power to that, I should be able to open it.

Leaning towards having this thing towed to BMW.
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      01-23-2022, 11:05 AM   #4
MarcoZandrini
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Hookup power and the press the start button without stepping on the brake pedal.
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      01-23-2022, 11:15 AM   #5
redgt00
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Just hooked up the booster again for fun. Tried engine start mode and charge mode. No power is getting to the car. The only thing that happens is the fan turns on and starts blowing.

I'd think that the terminals in the engine bay would supply power to the car?
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      01-23-2022, 02:19 PM   #6
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With all that you did with the back seat you should be able to feed some stiff wire into the trunk and pop the seat release. Most likely the reason you cant get power is the way you pulled the positive off the battery, must have separated the feed to the front.
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      01-23-2022, 02:54 PM   #7
redgt00
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Quote:
Originally Posted by jzeiler4 View Post
With all that you did with the back seat you should be able to feed some stiff wire into the trunk and pop the seat release. Most likely the reason you cant get power is the way you pulled the positive off the battery, must have separated the feed to the front.
That's what I'm thinking. Wish I had just disconnected the negative terminal.
It's really tight back there. I know people have gotten in there, but I just can't see where I'm going if I stick something in there. I tried a 1/2" piece of pex pipe but couldn't get it in there.

If I had some sort of cable camera I could at least see what I'm doing.
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      01-27-2022, 09:18 AM   #8
redgt00
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Just an update for anyone reading this in the future:

ALWAYS DISCONNECT THE NEGATIVE TERMINAL FROM THE BATTERY FIRST.

I didn't even fully disconnect the positive cable. I disconnected another cable running to the positive side. I was a bit confused obviously, but the car shut down so I thought I was good to go.

I ended up towing the car to BMW. Their tech was able to tap into the wiring somewhere and release the latch to the trunk for the small fee of $222

As an added bonus, I apparently broke the coolant line that comes off the coolant reservoir. It sounds like these break all the time. Prop to BMW sarasota for being straight up with me and telling me I could fix that myself. Quote from them would have been around $400. I got the part for $40 and paid to tow the car back home.

All in all I'm calling this a win. I was out about $450 for the tows, VCG, coolant hose and labor for BMW to open the trunk. Still cheaper than paying them to do my VCG lol.

Last edited by redgt00; 01-27-2022 at 09:20 AM.. Reason: added info
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      01-27-2022, 04:18 PM   #9
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Sucks you had to pay that much but I'm glad you got a resolution!

Everytime I disconnect the battery, I always put down the back seats first.

Def kudos to that dealer for giving you a shot at the cheaper option for that expansion tank hose. I actually just keep a new one in my garage as a spare, lol.
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