stormtrooper57

Evening all, first post here after many years of browsing. Hoping somebody can share some knowledge or insight on this one.

Intermittently, when powering off the car using the start/stop button, all power will cut as though the battery is dead. This means the car does not allow the key fob to be ejected and is stuck in the barrel. This issue is quickly remedied by opening and then closing the door, which wakes the car back up. All the dash lights flash for a split second and she's back in the room - but everything needs resetting, the clock time goes, as does the mpg reading stored from the last trip. Although this method gets me going again, I'm concerned the damage this might be doing to other modules and/or components on each occurrence.

Just an added FYI, the tailgate wire looms are a mess, and have been previously poorly spliced from a donor car (there's an extra couples of plugs and wire that doesn't go anywhere, so I'm presuming it had an optional extra like an electric tailgate). I currently have no central locking, no rear wiper or split tailgate glass functionality, so I am wondering if something is shorting it out. My CCC iDrive is also a bit dicky.

In my research, I've found a few threads of folks having problems like this when trying to turn on the car, or strange power cuts when driving... but never when turning it off, hence starting this thread. Any thoughts or musings are greatly appreciated, but if anyone can recommend a reputable auto electrician in the south of England I'd be most grateful too. I own an LCI 525d touring auto.

Thanks in advance.

donpb

It would help you immensely to purchase a BMW specific code reader.

stormtrooper57

I have a Carly scanner on the way - do you have any recommendations?

donpb

I would not recommend it but since you already ordered, might as well use it.

nickstep

Hello. I just fixed a 2007 525xi with this identical issue (frequently when turning off car, loses power, key fob won't eject, car "wakes up" again by opening a door or worst case by performing a battery reset..no relevant fault codes will be stored). Replace the negative battery cable with integrated IBS (intelligent battery sensor) from HELLA (OEM manufacturer). You will most likely need to buy 2 small additional retrofit wire harnesses to be able to plug in the new and updated IBS to the existing vehicle connectors. I also VERY HIGHLY recommend replacing the vehicle battery at the same time with an OEM AGM battery and properly registering the battery exchange in the DME. Registration of the battery exchange informs the DME and all relevant control modules of the repair and clears their battery "memory". It basically resets every modules battery health information so that they can resume normal operation immediately and not shut down the vehicle electronics based on poor information from the bad IBS (in an attempt to prevent total battery discharge). Good luck! Let me know how you make out!