Rex wont turn on at highway speeds...

[Onesince40]

I just purchased a 2014 I3 Rex and while driving on the highway this weekend, at about 5 miles left (10% EV battery) the car starts slowing down and on the right side of the screen the "ePower" Baby Blue and Gray bars disappeared.

I had to pull over on the side of the highway as the car slowed down to a stop and was dead! Now you can here the Rex trying to kick in but it sputters and never kicks in.

then I get a charging system malfunction and I finally had to get towed to the nearest charging station where I charged and the car behaved like normal.

I forced myself to do it again to video tape it and prove that I am not that crazy....

Link 1 from 5 miles range to dead: https://www.youtube.com/watch?v=uRYqCmgcEOY
Link 2 dead to Charge system malfunction: https://youtube.com/shorts/v8AwJ6ZLcBM


anyone deal with this craziness???

 

[o2cool4g63]

Have you tried to manually start the rex engine to see if it would even start?

Open the hatch
Get in the car and close the door
Press start button to turn on without brake
Accerator pedal down max and hold
Press brake 3 times with your left foot
Let off the accerator pedal while holding brake and press the start button

 

[Onesince40]

I tried the Open Trunk, Holding the Gas Pedal, and the pump brake 3 times, thing, and Rex tries to start as I get the yellow text that says Emissions mode has been started, but all you hear is Rex sputter, it tries to start but doesnt...

 

[o2cool4g63]

Then I would check spark plug, oil and air filter oil filter next. Do you know when was it last serviced or when rex was started last? Do you know how to check battery health from main display?

 

[EvanstonI3]

It is not supposed to come on until 6% Battery left. For a 9 year old battery like yours, battery degradation is most likely not allowing you to actually get to 6% battery left without running out of electrons.

I am seeing a few more anecdotal cases like this with 2014 models and I think that, other than a new HV traction battery, your only option is to get the BimmerCODE app along with a compatible OBDII dongle and change where "HSOC" (Hold State of Charge) comes on. In other words, make the REX come on sooner. I don't have a REX and have not done this so I can't instruct you further.

edit to add: you should follow the directions of other posts to make sure the REX can actually turn on as well. There is a common issue with a Fuel Pump Relay that fails, which prevents the REX from starting. It is apparently very easy to simply swap out.

 

[Onesince40]

Thank you all, I just ordered a ODBII and will try the HSOC option and also enable the rest of the gas tank, but its so concerning that Rex is going haywire like this…

 

[Onesince40]

And….I think this is it…..Software Issue

https://www.bmwblog.com/2017/04/17/bmw-address-issue-incorrect-state-charge-readings-i3/

 

[alohart]

And….I think this is it…..Software Issue

https://www.bmwblog.com/2017/04/17/bmw-address-issue-incorrect-state-charge-readings-i3/

If the REx engine would start and run normally, I would agree. It seems like the REx engine is trying to start automatically at ~6% charge level, but something is preventing it from running. There must be at least one DTC that's been recorded that could indicate the problem. Some common problems are a bad fuel pump relay, bad spark plugs or spark plug coils, or a bad crankshaft (or maybe camshaft) position sensor.

 

[Onesince40]

I was just able to start the Range Extender in Emmision mode, it ran for 15 or so minutes then shut off, so I did it again, and it worked, so its just when the battery is low where Rex wont turn on….

 

[alohart]

I was just able to start the Range Extender in Emmision mode, it ran for 15 or so minutes then shut off, so I did it again, and it worked, so its just when the battery is low where Rex wont turn on….

After watching the video showing the power bars starting to disappear at ~8% charge level, I agree that the BMS' idea of the charge level must be incorrect. BMW has a software fix for this. The power bars shouldn't start disappearing until the displayed charge level drops to ~2%. By then, the REx engine should have started to prevent the charge level from continuing to drop.

It wasn't easy for me to see the power bars. It almost looked like most of them suddenly disappeared within a few seconds. If that's what happened, the voltage of one of the battery cells might have suddenly decreased which isn't normal. It might be worth installing the mi3 app (iOS) or the electrified app (Android) to learn the minimum and maximum voltages, charge levels, and capacities of all 96 battery cells at a low charge level. That could indicate whether a weak cell or cells might be causing problems at low charge levels.

It also seems like the REx engine isn't behaving normally. You wrote that it wouldn't start and sputtered but now it seems to run normally. The charging error that was displayed might have been due to the REx engine not starting.