looking for some help with 2015 REX

Hello everybody! My wife has been driving her 2015 Rex since 2017 and absolutely loves the car. It has a bit over 50k miles now and worked flawlessly until last week when we experienced the 12V battery drama. Had I only read the forums before! The car shut down, I replaced the battery, bought bimmerlink to register, but have a really hard time with the red "Drivetrain: Stop carefully" message in the display (symbol showing the rex). I cannot wake the car up any more. The cooling fan is on (so I pulled the relais to keep 12V from draining too fast) and I have a yellow "Transmission Malfunction" message with the ignition off. I cannot get into any gear and Bimmerlink is unable to erase all errors. Since the car worked fine before, I hesitate to dig deeper and pull off panels to look for corrosion. Looking online I haven't found a good strategy for troubleshooting from here. Any advice on my particular situation is very much appreciated. Thanks a lot for reading all this.

1: did you make sure the 12v replacement was fully charged before installing it?

2: Plug the car into the charger and let it sit overnight, if not longer to let the computers "talk" to each other. It may seem odd but this simple procedure has saved many others in the past with a similar situation. There is no way to rush it.

Thanks for the tip. I may not have done this long enough before. I just plugged it in with full 12v battery, the white charging light came on for a few minutes (car is fully charged) and then turned off. Keeping fingers crossed….

No luck! Car was plugged in with a full 12V battery for 30+ hours. The yellow transmission malfunction is displayed when I get in the car with the ignition off. Then pushing the ignition button, the red "drivetrain: stop carefully" comes on. Plus all the other warnings and reminders. The car does not start. I cannot switch it to Neutral, so I could push it out of the garage and onto a trailer. I read that holding the trip reset button could reset the computer and the volume button would do something similar after 20s, but there is absolutely nothing happening. Since both warnings, the yellow transmission and the red drive, show the symbol for the REX, I think the problem must lie there. I'm thinking to pull fuses to hard reset, but is there a recommended sequence? Really, what I need is a travelling i3 expert Thanks for any ideas and suggestions.

If you haven't done so, download and license BimmerLink, buy an appropriate ODB to WiFi or Bluetooth adapter from Amazon, and clear all diagnostic trouble codes (DTC's). A DTC might be preventing your i3 from operating normally.

Unfortunately BimmerLink is unable to clear the faults. There are so many codes, especially in accumulator and motor electronics. I still have the drivetrain error (Rex) which prevents the car from starting… I think I have no choice at this point but to figure out a way to move and load the car up. Unless someone knows a traveling i3 tech around Asheville/Greenville?

This might be a shot in the dark, but did you fully reconnect the high voltage battery disconnect switch in the frunk after you installed the new 12 volt battery (assuming you disconnected it prior to battery installation)? Some people have had difficulties doing this after a 12 volt battery replacement, and the disconnect switch needs to be fully reconnected.

Thanks for your comment. Yes, I disconnected and the (orange) plug showed OFF - the hole for a padlock was complete. Then back to ON after the replacement. The plug itself is a little strange, I agree. You have to depress the small tab on the bottom to switch. It feels odd. In the meantime I read on another post that my problem might be that the 12V from the new battery does not reach this plug. I have yet to check that. There could be some sort of Pyro fuse or wiring damage. I would think that a fuse might be blown during the battery swap but cannot imagine to have created cable damage. The cables coming off the + connector on the battery all look very good, no chafing or other damage visible. Does anyone have any experience bridging the 12V supply from the battery directly to the High Voltage plug? Supposedly the drivetrain error may be caused by the HV system not being activated correctly.... I have a more experienced tech coming to the garage and will report back... Thanks again!

Tech found that the EME is no longer communicating. Apparently it had failed 2 miles before my wife turned off the car in the garage. This probably killed the old 12v battery since it no longer charged. Ok, so the root cause now shifted to the EME module. Before I order a wrecker to bring the car to a shop and pay 7K or so I would like to see if I can remove the EME and have an electronics guy take a look at it. Has anyone here experience with removing this from a Rex? The little bit of info I find online may suggest that the whole electric drivetrain has to come out? Thanks for any advice!!

buelltours said:

Before I order a wrecker to bring the car to a shop and pay 7K or so I would like to see if I can remove the EME and have an electronics guy take a look at it. Has anyone here experience with removing this from a Rex? The little bit of info I find online may suggest that the whole electric drivetrain has to come out?

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The official BMW procedure involves dropping the drivetrain. The high labor cost adds to BMW's very high total cost of replacing the EME, reportedly more than $10k. I don't know whether there's a way to remove the EME without dropping the drivetrain.

Auto-tec Diagnostics repairs i3 EME's for a fraction of BMW's price for a new one. They are located in the U.K., so depending on where you live, that could be a positive or a negative.