Trunk no longer opens/close after disconnecting the battery

[jlam86]

Hey fellas,

I was installing an amplifier into my car so I disconnected the battery to complete the job safely. Upon reconnecting it, the trunk stopped working, 4x4 and dtc failures came on. I remember reading somewhere it's due to the steering sensor that causes this issue and to turn it fully to the left then fully to the right and it will take care of the issue. Surprisingly it worked, so the 4x4 and dtc is active again but I can't figure out the trunk.

The latch unlatches when using the remote, console and rear latch but it won't roll up nor will it come down when you push the button to close the trunk. The red button does not even illuminate. Could I have popped a fuse when reconnecting the battery? So messed up... I wanted to look for the fuse number in my owners manual but it is stuck in my glove box and that won't open too!

Any ideas?

[jlam86]

Since I didn't get a single response to this thread, I figure, perhaps people were just unfamiliar with the issue. I took it to the dealer and I will shed some light in hope that if every anyone runs into the issue, this might contribute to your check list of things to look for.

So, issue is..Trunk was completely inoperable (remote, console) nada. I had to use the manual pull cable on the inside and push the gate open simultaneously. Also, glove box in front of passenger seat was not opening (apparently this is tied into the same module as the trunk, JBE).

BMW diagnosed that I had a corroded ISB cable. This ISB cable senses voltage and keeps the JBE (trunk/glove box/ and whatever else is connected to it) operating. Since my cable was "corroded", even though it's located in the cabin of the vehicle, the module sensed a low voltage and shut this module down to conserve energy.

Coles notes: Check the ISB cable. It's connected directly off the battery according to the service staff.

Hope this helps someone down the road.

[m3the01]

So they fixed this for free?

Strange...just to be clear u only pulled the negative terminal and upon reattaching these problems came up?

[jlam86]

That is correct. Strange but oh well. It's working again. Surprised to see that the glove box is electronic too. I think that is a silly design. God forbid if you get into an accident and the battery goes? All your belongings are going to be stuck in the glove box.

Yes they fixed it for free. Under warranty period still.

[StumpyPete]

I had a similar one when I was doing some work. Disconnected the battery and on reconnect - nothing. I pulled the Battery sensor cable and that enabled the car to start, reconnected the battery sensor and got all the warning lights. However for me the cure was simple - drive around the block. Once I had done that all the systems recalibrated and I was fine. No further issues until I got rid of the car.

[m3the01]

Is there a special procedure for pulling the negative terminal or something?

Seems trivial, but obviously it is not anymore...:-)

[jlam86]

I was wondering about this myself to be quite honest. With so many electronics in these cars, it really makes me wonder if there is a more guaranteed peace of mind way of doing this.

[m3the01]

I hear you, what is BMW's procedure when needing to disconnect the battery? Ive heard a lot of people with issues after boosting or disconnecting the battery.